Operando unraveling photothermal-promoted dynamic active-sites generation in NiFe2O4 for markedly enhanced oxygen evolution

Photothermal enhanced bifunctional catalyst for overall water splitting with phosphide heterojunction Fe2P-CoMoP

The development of cost-effective bifunctional electrocatalysts remains a great challenge. In this work, high-performance Fe2P-CoMoP/NF catalysts were prepared using the strategy of constructing phosphide heterostructures with localized photothermal effect. At 10 mA·cm-2, the HER overpotential of Fe2P-CoMoP/NF is 30.8 mV and the OER overpotential is 180.9 mV. Compared to Fe2P/NF and CoMoP/NF, the higher content of oxygen vacancies in the phosphorylated heterostructure Fe2P-CoMoP/NF has the potential to enhance intrinsic activity and improve the photothermal effect. With the assistance of localized photothermal effect, the HER (η100 = 72.7 mV) and OER (η100 = 252.3 mV) overpotentials of Fe2P-CoMoP/NF decreased by 35.8 % and 9.9 %, which were more significant than those of CoMoP/NF and Fe2P/NF. Meanwhile, the Fe2P-CoMoP/NF catalyst has excellent stability, maintaining 96 % at -500 mA·cm-2 and 94 % at 300 mA·cm-2 after 100 h. In addition, overall water splitting can be carried out using solar panels with a voltage of 1.42 V, which shows its potential for application in combination with sustainable energy sources.

Catalytic synergism in heterostructural Ta-doped Mo-Ni-S nanospheres: an efficient bifunctional catalyst for water splitting

Designing suitable and efficient electrocatalysts for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial for sustainable hydrogen production. To date, extensive studies have focused on transition metal chalcogenides (TMSs) due to their unique electronic structure and strong ability to be modified. Herein, we reported a Ta-doped MoS2/NiS catalyst supported on NF with a stable hierarchical nanosphere structure (Ta-MNS). The synergy between the MoS2 and NiS phases in the same plane enhanced the mechanical strength and exposed more active sites, while Ta5+ was applied to adjust the electronic structure, resulting in a well-dispersed and flexible morphology. Moreover, the formation of the -S-Ta5+-S- bridge was proposed as a significant factor in enhancing the link between components at the active phase and further promoting electron transfer. As a result, for HER, the synthesized Ta-MNS required overpotentials of only 35 and 127 mV at current densities of 10 and 100 mA cm-2, respectively. Furthermore, it demonstrated outstanding performance for OER and excellent stability, maintaining stable operation for more than 80 h. This paves a new avenue for the design of novel catalysts for water splitting.

Photothermal-promoted anion exchange membrane seawater electrolysis on a nickel-molybdenum-based catalyst

Exploring active, durable catalysts and utilizing external renewable energy sources offer notable opportunities for advancing seawater electrolysis. Here, a multifunctional NiMo-based catalyst (NiMo-H2) composed of bimetallic Ni0.91Mo0.09 nanoparticles on MoO2 nanorods is demonstrated for the alkaline seawater hydrogen evolution reaction. The alloying effect and the nanorod-nanoparticle structure endow this catalyst with high structural stability, rapid electron transfer, and a large surface area. The in situ-generated alloyed nanoparticles have notable light absorption and photothermal conversion capabilities, while the vertically grown nanorods suppress diffuse reflection, enabling efficient localized photoheating. Consequently, light irradiation boosts the catalyst's activity and it works stably at a current density of 500 mA cm-2 in alkaline seawater. We then assemble the NiMo-H2||NiFe LDH pair in a photothermal anion exchange membrane electrolyzer, and it requires approximately 1.6 V to drive a current of 0.45 A, demonstrating robust durability in overall alkaline seawater electrolysis. This photothermal-promoted seawater electrolysis system shows notable potential for hydrogen production from seawater.

Insight into the structural reconstruction of alkaline water oxidation electrocatalysts

The oxygen-evolution reaction (OER) is an indispensable component of various energy storage and conversion electrocatalytic systems. However, the slow reaction kinetics have forced the development of advanced, efficient, and inexpensive OER electrocatalysts to break through the bottleneck of its application. Recently, the structural reconstruction of precatalysts has provided a promising avenue to boost the catalytic activity of electrocatalysts. Structural reconstruction implies atomic rearrangement and composition change of the pristine catalytic materials, which is a very complex process. Therefore, it is very crucial to have a deep understanding of the reconstruction chemical process and then modulate the reconstruction by deliberate design of electrochemical conditions and precatalysts. However, a systematic review of the structural reconstruction process, research methods, influencing factors and structure-performance relationship remains elusive, significantly impeding the further developments of efficient electrocatalysts based on structural reconstruction chemistry. This critical review is dedicated to providing a deep insight into the structural reconstruction during alkaline water oxidation, comprehensively summarizing the basic research methods to understand the structural evolution process and various factors affecting the structural reconstruction process, and providing a reference and basis for regulating the dynamic reconstruction. Moreover, the impact of reconstruction on the structure and performance is also covered. Finally, challenges and perspectives for the future study on structural reconstruction are discussed. This review will offer future guidelines for the rational development of state-of-the-art OER electrocatalysts.

Modulation of Electrochemical Reactions through External Stimuli: Applications in Oxygen Evolution Reaction and Beyond

Electrochemical water splitting is a promising method for generating green hydrogen gas, offering a sustainable approach to addressing global energy challenges. However, the sluggish kinetics of the anodic oxygen evolution reaction (OER) poses a great obstacle to its practical application. Recently, increasing attention has been focused on introducing various external stimuli to modify the OER process. Despite significant enhancement in catalytic performance, an in-depth understanding of the origin of superior OER activity contributed by the external stimuli remains elusive, which significantly hinders the further development of highly efficient and durable water electrolyzed devices. Herein, this review systematically summarizes the recent advancements in the understanding of various external stimuli, including photon irradiation, applied magnetic field, and thermal heating, etc., to boost OER activities. In particular, the underlying mechanisms of external stimuli to promote species transfer, modify the electronic structure of electrocatalysts, and accelerate structural reconstruction are highlighted. Additionally, applications of external stimuli in other electrocatalytic reactions are also presented. Finally, several remaining challenges and future opportunities are discussed, providing insights that could further the study of external stimuli in electrocatalytic reactions and support the rational design of highly efficient energy storage and conversion devices.

Triggering Oxygen Redox Cycles in Nickel Ferrite by Octahedral Geometry Engineering for Enhancing Oxygen Evolution

Spinel-type nickel ferrite (NixFe3-xO4, x≤1) is a widely used electrocatalyst for the oxygen evolution reaction (OER). Due to the lower hybridization of metal-d and oxygen-p orbitals, the OER process on NixFe3-xO4 follows the sluggish adsorbate evolution mechanism (AEM). Generally, activating the lattice oxygen to trigger the lattice-oxygen-mediated mechanism (LOM) can enhance the OER activity. Herein, to trigger the LOM pathway while maintaining high stability, iron foam (IF)-supported Ni0.75Fe2.25O4 (NiFeO) with geometrical defects of [NiO6] (nickel cation coordinated with six oxygen anions) units and higher ratio of Fe to Ni cations in octahedral sites (d-NiFeHRO/IF) is prepared by ion-exchanging with polar aprotic solvent followed by annealing. As a result, as-synthesized d-NiFeHRO/IF exhibits excellent activity (at 295 mV overpotential to achieve 100 mA cm-2), fast kinetics (Tafel slope of only 34.6 mV dec-1), and high stability (maintaining a current density of 100 mA cm-2 over 130 h) for the OER. The theoretical calculations reveal that the construction of octahedral defect in NixFe3-xO4 enhances the overlap of Fe-d and O-p orbitals, which can activate the lattice oxygen. Therefore, increasing the ratio of Fe to Ni will further improve the lattice oxygen redox activity, and thus trigger the fast LOM pathway, ultimately facilitating the OER process.

Synergistic enhancement of electrochemical alcohol oxidation by combining NiV-layered double hydroxide with an aminoxyl radical

Electrochemical alcohol oxidation (EAO) represents an effective method for the production of high-value carbonyl products. However, its industrial viability is hindered by suboptimal efficiency stemming from low reaction rates. Here, we present a synergistic electrocatalysis approach that integrates an active electrode and aminoxyl radical to enhance the performance of EAO. The optimal aminoxyl radical (4-acetamido-2,2,6,6-tetramethylpiperidine 1-oxyl) and Ni0.67V0.33-layered double hydroxide (LDH) are screen as cooperative electrocatalysts by integrating theoretical predictions and experiments. The Ni0.67V0.33-LDH facilitates the adsorption and activation of N-(1-hydroxy-2,2,6,6-tetramethylpiperidin-4-yl)acetamide (ACTH) via interactions with ketonic oxygen, thereby improving selectivity and yield at high current densities. The electrolysis process is scaled up to produce 200 g of the steroid carbonyl product 8b (19-Aldoandrostenedione), achieving a yield of 91% and a productivity of 243 g h-1. These results represent a promising method for accelerating electron transfer to enhance alcohol oxidation, highlighting its potential for practical electrosynthesis applications.

Fluorine-Induced Lattice Oxygen Participation in 2D Layered Double Hydroxide/MXene Hybrids for Efficient Oxygen Evolution

In oxygen evolution reaction (OER), the participation of lattice oxygen can break the limitation of adsorption evolution mechanism, but the activation of lattice oxygen remains a critical challenge. Herein, a surface fluorinated highly active 2D/2D FeNi layered double hydroxide/MXene (F-LDH/MX) is demonstrated, boosting OER with the enhanced lattice-oxygen-mediated path. The introduction of fluorine promotes the self-evolution of catalyst in an alkaline environment, even without an external current. It further accelerates the formation of active metal oxyhydroxides with abundant oxygen vacancies under the operating potential. The introduced oxygen vacancy activates the lattice oxygen, increasing the proportion of lattice oxygen mechanism in OER. Owing to the synergistic effects of the 2D/2D hierarchical structure and the modulated active surface, F-LDH/MX possesses excellent electrochemical performances, including a low overpotential of 251 mV at 10 mA cm-2, a low Tafel slope of 40.28 mV dec-1, and robust stability. The water electrolyzer system with F-LDH/MX as the anode offers the benchmark current density at a low cell voltage of 1.53 V, while the Zn-air battery with F-LDH/MX as the air electrode exhibits a higher power density of 75.43 mW cm-2. This study presents a promising strategy to design highly active electrocatalysts for energy conversion and storage.

Synergistic Contribution of the Strain and Magnetic Field in Ferromagnetic NiMnIn Heusler Alloy Films for the Hydrogen Evolution Reaction

The external field-assisted hydrogen evolution reaction (HER), beyond modifying electrocatalysts themselves, has garnered significant research attention. However, achieving synergy between multiple fields to enhance the HER performance remains challenging and is not well-explored. Here, NiMnIn Heusler alloy thin films are fabricated using pulsed laser deposition on flexional Cu substrates. Due to the different adsorption free energy under tensile strain (TS) and compressive strain (CS), the most significant enhancement of the electrocatalytic HER activities for the NiMnIn film is observed in the 1.9% TS state, while the CS state of the NiMnIn film shows negative effects. Furthermore, when an external magnetic field is coupled to the 1.9% tensile-strained NiMnIn film, the total overpotential is reduced by 28.6% at a current density of -50 mA cm-2. This improvement is attributed to a synergistic effect that enhances the H adsorption stability and accelerates the H2 desorption process. This work demonstrates the effectiveness of combining multiple external fields and presents a promising strategy for advancing electrocatalysis.

Stability of electrocatalytic OER: from principle to application

Hydrogen energy, derived from the electrolysis of water using renewable energy sources such as solar, wind, and hydroelectric power, is considered a promising form of energy to address the energy crisis. However, the anodic oxygen evolution reaction (OER) poses limitations due to sluggish kinetics. Apart from high catalytic activity, the long-term stability of electrocatalytic OER has garnered significant attention. To date, several research studies have been conducted to explore stable electrocatalysts for the OER. A comprehensive review is urgently warranted to provide a concise overview of the recent advancements in the electrocatalytic OER stability, encompassing both electrocatalyst and device developments. This review aims to succinctly summarize the primary factors influencing OER stability, including morphological/phase change and electrocatalyst dissolution, as well as mechanical detachment, alongside chemical, mechanical, and operational degradation observed in devices. Furthermore, an overview of contemporary approaches to enhance stability is provided, encompassing electrocatalyst design (structural regulation, protective layer coating, and stable substrate anchoring) and device optimization (bipolar plates, gas diffusion layers, and membranes). Hopefully, more attention will be paid to ensuring the stable operation of electrocatalytic OER and the future large-scale water electrolysis applications. This review presents design principles aimed at addressing challenges related to the stability of electrocatalytic OER.

Unlocking Efficiency: Minimizing Energy Loss in Electrocatalysts for Water Splitting

Catalysts play a crucial role in water electrolysis by reducing the energy barriers for hydrogen and oxygen evolution reactions (HER and OER). Research aims to enhance the intrinsic activities of potential catalysts through material selection, microstructure design, and various engineering techniques. However, the energy consumption of catalysts has often been overlooked due to the intricate interplay among catalyst microstructure, dimensionality, catalyst-electrolyte-gas dynamics, surface chemistry, electron transport within electrodes, and electron transfer among electrode components. Efficient catalyst development for high-current-density applications is essential to meet the increasing demand for green hydrogen. This involves transforming catalysts with high intrinsic activities into electrodes capable of sustaining high current densities. This review focuses on current improvement strategies of mass exchange, charge transfer, and reducing electrode resistance to decrease energy consumption. It aims to bridge the gap between laboratory-developed, highly efficient catalysts and industrial applications regarding catalyst structural design, surface chemistry, and catalyst-electrode interplay, outlining the development roadmap of hierarchically structured electrode-based water electrolysis for minimizing energy loss in electrocatalysts for water splitting.

Catalyst-Support Interaction in Polyaniline-Supported Ni3Fe Oxide to Boost Oxygen Evolution Activities for Rechargeable Zn-Air Batteries

Catalyst-support interaction plays a crucial role in improving the catalytic activity of oxygen evolution reaction (OER). Here we modulate the catalyst-support interaction in polyaniline-supported Ni3Fe oxide (Ni3Fe oxide/PANI) with a robust hetero-interface, which significantly improves oxygen evolution activities with an overpotential of 270 mV at 10 mA cm-2 and specific activity of 2.08 mA cmECSA-2 at overpotential of 300 mV, 3.84-fold that of Ni3Fe oxide. It is revealed that the catalyst-support interaction between Ni3Fe oxide and PANI support enhances the Ni-O covalency via the interfacial Ni-N bond, thus promoting the charge and mass transfer on Ni3Fe oxide. Considering the excellent activity and stability, rechargeable Zn-air batteries with optimum Ni3Fe oxide/PANI are assembled, delivering a low charge voltage of 1.95 V to cycle for 400 h at 10 mA cm-2. The regulation of the effect of catalyst-support interaction on catalytic activity provides new possibilities for the future design of highly efficient OER catalysts.

Reasonable Design and Deep Insight of Efficient Integrated Photorechargeable Li-Ion Batteries by Using a Cu/CuO/Cu2S Electrode

Herein, Cu-foam-supported CuO nanowire arrays covered with Cu2S nanosheet substrates (Cu/CuO/Cu2S) are adopted as efficient photoelectrodes for photorechargeable lithium-ion batteries (PR-LIBs). The assembled PR-LIB exhibits remarkable solar energy conversion efficiency alongside superior lithium storage capabilities. Without an electrical power supply, the photocharged PR-LIB sustained a discharge process for 63.0 h under a constant current density of 0.05 mA cm-2. The corresponding solar-to-electrical energy conversion efficiency is 4.50%, which is an impressive achievement among recently reported contemporary technologies. Mechanism investigation shows that the Cu/CuO/Cu2S photogenerated carriers augment the extraction and insertion of Li+ according to different oxidation and reduction reactions in the charging and discharging reactions. This research delineates a refined model system and proposes innovative directions for developing efficient heterojunction photoelectrodes, significantly propelling the development of PR-LIB technology.

RuCo/ZrO2 Tandem Catalysts with Photothermal Confinement Effect for Enhanced CO2 Methanation

Photothermal CO2 methanation reaction represents a promising strategy for addressing CO2-related environmental issues. The presence of efficient tandem catalytic sites with a localized high-temperature is an effective pathway to enhance the performance of CO2 methanation. Here the bimetallic RuCo nanoparticles anchored on ZrO2 fiber cotton (RuCo/ZrO2) as a photothermal catalyst for CO2 methanation are prepared. A significant photothermal CO2 methanation performance with optimal CH4 selectivity (99%) and rate (169.93 mmol gcat -1 h-1) is achieved. The photothermal energy of the RuCo bimetallic nanoparticles, confined by the infrared insulation and low thermal conductivity of the ZrO2 fiber cotton (ZrO2 FC), provides a localized high-temperature. In situ spectroscopic experiments on RuCo/ZrO2, Ru/ZrO2, and Co/ZrO2 indicate that the construction of tandem catalytic sites, where the Co site favors CO2 conversion to CO while incorporating Ru enhances CO* adsorption for subsequent hydrogenation, results in a higher selectivity toward CH4. This work opens a new insight into designing tandem catalysts with a photothermal confinement effect in CO2 methanation reaction.

Amorphous/Crystalline Phases Mixed Nanosheets Array Rich in Oxygen Vacancies Boost Oxygen Evolution Reaction of Spinel Oxides in Alkaline Media

As promising oxygen evolution reaction (OER) catalysts, spinel-type oxides face the bottleneck of weak adsorption for oxygen-containing intermediates, so it is challenging to make a further breakthrough in remarkably lowering the OER overpotential. In this study, a novel strategy is proposed to substantially enhance the OER activity of spinel oxides based on amorphous/crystalline phases mixed spinel FeNi2O4 nanosheets array, enriched with oxygen vacancies, in situ grown on a nickel foam (NF). This unique architecture is achieved through a one-step millisecond laser direct writing method. The presence of amorphous phases with abundant oxygen vacancies significantly enhances the adsorption of oxygen-containing intermediates and changes the rate-determining step from OH*→O* to O*→OOH*, which greatly reduces the thermodynamic energy barrier. Moreover, the crystalline phase interweaving with amorphous domains serves as a conductive shortcut to facilitate rapid electron transfer from active sites in the amorphous domain to NF, guaranteeing fast OER kinetics. Such an anodic electrode exhibits a nearly ten fold enhancement in OER intrinsic activity compared to the pristine counterpart. Remarkably, it demonstrates record-low overpotentials of 246 and 315 mV at 50 and 500 mA cm-2 in 1 m KOH with superior long-term stability, outperforming other NiFe-based spinel oxides catalysts.

Electrochemically Induced Ru/CoOOH Synergistic Catalyst as Bifunctional Electrode Materials for Alkaline Overall Water Splitting

Efficient and affordable price bifunctional electrocatalysts based on transition metal oxides for oxygen and hydrogen evolution reactions have a balanced efficiency, but it remains a significant challenge to control their activity and durability. Herein, a trace Ru (0.74 wt.%) decorated ultrathin CoOOH nanosheets (≈4 nm) supported on the surface of nickel foam (Ru/CoOOH@NF) is rationally designed via an electrochemically induced strategy to effectively drive the electrolysis of alkaline overall water splitting. The as-synthesized Ru/CoOOH@NF electrocatalysts integrate the advantages of a large number of different HER (Ru nanoclusters) and OER (CoOOH nanosheets) active sites as well as strong in-suit structure stability, thereby exhibiting exceptional catalytic activity. In particular, the ultra-low overpotential of the HER (36 mV) and the OER (264 mV) are implemented to achieve 10 mA cm-2. Experimental and theoretical calculations also reveal that Ru/CoOOH@NF possesses high intrinsic conductivity, which facilitates electron release from H2O and H-OH bond breakage and accelerates electron/mass transfer by regulating the charge distribution. This work provides a new avenue for the rational design of low-cost and high-activity bifunctional electrocatalysts for large-scale water-splitting technology and expects to help contribute to the creation of various hybrid electrocatalysts.

Linker Mediated Electronic-State Manipulation of Conjugated Organic Polymers Enabling Highly Efficient Oxygen Reduction

Conjugated polymers with tailorable composition and microarchitecture are propitious for modulating catalytic properties and deciphering inherent structure-performance relationships. Herein, we report a facile linker engineering strategy to manipulate the electronic states of metallophthalocyanine conjugated polymers and uncover the vital role of organic linkers in facilitating electrocatalytic oxygen reduction reaction (ORR). Specifically, a set of cobalt phthalocyanine conjugated polymers (CoPc-CPs) wrapped onto carbon nanotubes (denoted CNTs@CoPc-CPs) are judiciously crafted via in situ assembling square-planar cobalt tetraaminophthalocyanine (CoPc(NH2)4) with different linear aromatic dialdehyde-based organic linkers in the presence of CNTs. Intriguingly, upon varying the electronic characteristic of organic linkers from terephthalaldehyde (TA) to 2,5-thiophenedicarboxaldehyde (TDA) and then to thieno/thiophene-2,5-dicarboxaldehyde (bTDA), their corresponding CNTs@CoPc-CPs exhibit gradually improved electrocatalytic ORR performance. More importantly, theoretical calculations reveal that the charge transfer from CoPc units to electron-withdrawing linkers (i.e., TDA and bTDA) drives the delocalization of Co d-orbital electrons, thereby downshifting the Co d-band energy level. Accordingly, the active Co centers with more positive valence state exhibit optimized binding energy toward ORR-relevant intermediates and thus a balanced adsorption/desorption pathway that endows significant enhancement in electrocatalytic ORR. This work demonstrates a molecular-level engineering route for rationally designing efficient polymer catalysts and gaining insightful understanding of electrocatalytic mechanisms.

Deciphering in-situ surface reconstruction in two-dimensional CdPS3 nanosheets for efficient biomass hydrogenation

Steering on the intrinsic active site of an electrode material is essential for efficient electrochemical biomass upgrading to valuable chemicals with high selectivity. Herein, we show that an in-situ surface reconstruction of a two-dimensional layered CdPS3 nanosheet electrocatalyst, triggered by electrolyte, facilitates efficient 5-hydroxymethylfurfural (HMF) hydrogenation to 2,5-bis(hydroxymethyl)furan (BHMF) under ambient condition. The in-situ Raman spectroscopy and comprehensive post-mortem catalyst characterizations evidence the construction of a surface-bounded CdS layer on CdPS3 to form CdPS3/CdS heterostructure. This electrocatalyst demonstrates promising catalytic activity, achieving a Faradaic efficiency for BHMF reaching 91.3 ± 2.3 % and a yield of 4.96 ± 0.16 mg/h at - 0.7 V versus reversible hydrogen electrode. Density functional theory calculations reveal that the in-situ generated CdPS3/CdS interface plays a pivotal role in optimizing the adsorption of HMF* and H* intermediate, thus facilitating the HMF hydrogenation process. Furthermore, the reconstructed CdPS3/CdS heterostructure cathode, when coupled with MnCo2O4.5 anode, enables simultaneous BHMF and formate synthesis from HMF and glycerol substrates with high efficiency.

Zn-based batteries for sustainable energy storage: strategies and mechanisms

Batteries play a pivotal role in various electrochemical energy storage systems, functioning as essential components to enhance energy utilization efficiency and expedite the realization of energy and environmental sustainability. Zn-based batteries have attracted increasing attention as a promising alternative to lithium-ion batteries owing to their cost effectiveness, enhanced intrinsic safety, and favorable electrochemical performance. In this context, substantial endeavors have been dedicated to crafting and advancing high-performance Zn-based batteries. However, some challenges, including limited discharging capacity, low operating voltage, low energy density, short cycle life, and complicated energy storage mechanism, need to be addressed in order to render large-scale practical applications. In this review, we comprehensively present recent advances in designing high-performance Zn-based batteries and in elucidating energy storage mechanisms. First, various redox mechanisms in Zn-based batteries are systematically summarized, including insertion-type, conversion-type, coordination-type, and catalysis-type mechanisms. Subsequently, the design strategies aiming at enhancing the electrochemical performance of Zn-based batteries are underscored, focusing on several aspects, including output voltage, capacity, energy density, and cycle life. Finally, challenges and future prospects of Zn-based batteries are discussed.

Generic heterostructure interfaces bound to Co9S8 for efficient overall water splitting supported by photothermal

The increase of reaction temperature of electrocatalysts and the construction of heterogeneous structures is regarded as an efficient method to improve the electrocatalytic water splitting activity. Here, we report an approach to enhance the local heat and active sites of the catalyst by building a heterostructure with Co9S8 to significantly improve its electrocatalytic performance. The as-fabricated Co9S8@Ce-NiCo LDH/NF electrode possesses a notable photothermal ability, as it effectively converts near-infrared (NIR) light into the local heat, owing to its significant optical absorption. Leveraging these favorable qualities, the prepared Co9S8@Ce-NiCo LDH/NF electrode showed impressive performance in both hydrogen evolution reaction (HER) (η100 = 144 mV) and oxygen evolution reaction (OER) (η100 = 229 mV) under NIR light. Compared to the absence of the NIR light, the presence of NIR irradiation leads to a 24.6 % increase in catalytic efficiency for HER and a 15.8 % increase for OER. Additionally, other dual-functional electrocatalysts like NiCo-P, NiFeMo, and NiFe(OH)x also demonstrated significantly enhanced photothermal effects and improved catalytic performance owing to the augmented photothermal conversion when combined with Co9S8. This work offers novel pathways for the development of photothermal-electrocatalytic systems that facilitate economically efficient and energy-conserving overall water splitting processes.

External Field-Responsive Ternary Non-Noble Metal Oxygen Electrocatalyst for Rechargeable Zinc-Air Batteries

Despite the increasing effort in advancing oxygen electrocatalysts for zinc-air batteries (ZABs), the performance development gradually reaches a plateau via only ameliorating the electrocatalyst materials. Herein, a new class of external field-responsive electrocatalyst comprising Ni0.5Mn0.5Fe2O4 stably dispersed on N-doped Ketjenblack (Ni0.5Mn0.5Fe2O4/N-KB) is developed via polymer-assisted strategy for practical ZABs. Briefly, the activity indicator ΔE is significantly decreased to 0.618 V upon photothermal assistance, far exceeding most reported electrocatalysts (generally >0.680 V). As a result, the photothermal electrocatalyst possesses comprehensive merits of excellent power density (319 mW cm-2), ultralong lifespan (5163 cycles at 25 mA cm-2), and outstanding rate performance (100 mA cm-2) for liquid ZABs, and superb temperature and deformation adaptability for flexible ZABs. Such improvement is attributed to the photothermal-heating-enabled synergy of promoted electrical conductivity, reactant-molecule motion, active area, and surface reconstruction, as revealed by operando Raman and simulation. The findings open vast possibilities toward more-energy-efficient energy applications.

Magnet-in-ferroelectric crystals exhibiting photomultiferroicity

Growing crystallographically incommensurate and dissimilar organic materials is fundamentally intriguing but challenging for the prominent cross-correlation phenomenon enabling unique magnetic, electronic, and optical functionalities. Here, we report the growth of molecular layered magnet-in-ferroelectric crystals, demonstrating photomanipulation of interfacial ferroic coupling. The heterocrystals exhibit striking photomagnetization and magnetoelectricity, resulting in photomultiferroic coupling and complete change of their color while inheriting ferroelectricity and magnetism from the parent phases. Under a light illumination, ferromagnetic resonance shifts of 910 Oe are observed in heterocrystals while showing a magnetization change of 0.015 emu/g. In addition, a noticeable magnetization change (8% of magnetization at a 1,000 Oe external field) in the vicinity of ferro-to-paraelectric transition is observed. The mechanistic electric-field-dependent studies suggest the photoinduced ferroelectric field effect responsible for the tailoring of photo-piezo-magnetism. The crystallographic analyses further evidence the lattice coupling of a magnet-in-ferroelectric heterocrystal system.

An enhanced electrocatalytic oxygen evolution reaction by the photothermal effect and its induced micro-electric field

Promoting better thermodynamics and kinetics of electrocatalysts is key to achieving an efficient electrocatalytic oxygen evolution reaction (OER). Utilizing the photothermal effect and micro-electric field of electrocatalysts is a promising approach to promote the sluggish OER. Herein, to reveal the relationship of the photothermal effect and its induced micro-electric field with OER performance, NiSx coupled NiFe(OH)y on nickel foam (NiSx@NiFe(OH)y/NF) is synthesized and subjected to the OER under near-infrared (NIR) light. Owing to the photothermal effect and its induced micro-electric field, the OER performance of NiSx@NiFe(OH)y/NF is significantly enhanced. Compared with no NIR light irradiation, the overpotential at 50 mA cm-2 and the Tafel slope of NiSx@NiFe(OH)y/NF under NIR light irradiation were 234.1 mV and 38.0 mV dec-1, which were lower by 12.4 mV and 7.1 mV dec-1, and it exhibited stable operation at 1.6 V vs. RHE for 8 h with 99% activity maintained. This work presents a novel inspiration to understand the photothermal effect-enhanced electrocatalytic OER.

Mesoporous Single Atom-Cluster Fe-N/C Oxygen Evolution Electrocatalysts Synthesized with Bottlebrush Block Copolymer-Templated Rapid Thermal Annealing

Current electrocatalysts for oxygen evolution reaction (OER) are either expensive (such as IrO2, RuO2) or/and exhibit high overpotential as well as sluggish kinetics. This article reports mesoporous earth-abundant iron (Fe)-nitrogen (N) doped carbon electrocatalysts with iron clusters and closely surrounding Fe-N4 active sites. Unique to this work is that the mechanically stable mesoporous carbon-matrix structure (79 nm in pore size) with well-dispersed nitrogen-coordinated Fe single atom-cluster is synthesized via rapid thermal annealing (RTA) within only minutes using a self-assembled bottlebrush block copolymer (BBCP) melamine-formaldehyde resin composite template. The resulting porous structure and domain size can be tuned with the degree of polymerization of the BBCP backbone, which increases the electrochemically active surface area and improves electron transfer and mass transport for an effective OER process. The optimized electrocatalyst shows a required potential of 1.48 V (versus RHE) to obtain the current density of 10 mA/cm2 in 1 M KOH aqueous electrolyte and a small Tafel slope of 55 mV/decade at a given overpotential of 250 mV, which is significantly lower than recently reported earth-abundant electrocatalysts. Importantly, the Fe single-atom nitrogen coordination environment facilitates the surface reconstruction into a highly active oxyhydroxide under OER conditions, as revealed by X-ray photoelectron spectroscopy and in situ Raman spectroscopy, while the atomic clusters boost the single atoms reactive sites to prevent demetalation during the OER process. Density functional theory (DFT) calculations support that the iron nitrogen environment and reconstructed oxyhydroxides are electrocatalytically active sites as the kinetics barrier is largely reduced. This work has opened a new avenue for simple, rapid synthesis of inexpensive, earth-abundant, tailorable, mechanically stable, mesoporous carbon-coordinated single-atom electrocatalysts that can be used for renewable energy production.

Dynamic in situ Formation of Cu2 O Sub-Nanoclusters through Photoinduced pseudo-Fehling's Reaction for Selective and Efficient Nitrate-to-Ammonia Photosynthesis

Copper (Cu) is evidenced to be effective for constructing advanced catalysts. In particular, Cu2 O is identified to be active for general catalytic reactions. However, conflicting results regarding the true structure-activity correlations between Cu2 O-based active sites and efficiencies are usually reported. The structure of Cu2 O undergoes dynamic evolution rather than remaining stable under working conditions, in which the actual reaction cannot proceed over the prefabricated Cu2 O sites. Therefore, the dynamic construction of Cu2 O active sites can be developed to promote catalytic efficiency and reveal the true structure-activity correlations. Herein, by introducing the redox pairs of Cu2+ and reducing sugar into a photocatalysis system, it is clarified that the Cu2 O sub-nanoclusters (NCs), working as novel active sites, are on-site constructed on the substrate via a photoinduced pseudo-Fehling's route. The realistic interfacial charge separation and transformation capacities are remarkably promoted by the dynamic Cu2 O NCs under the actual catalysis condition, which achieves a milestone efficiency for nitrate-to-ammonia photosynthesis, including the targets of production rate (1.98±0.04 mol gCu -1  h-1 ), conversion ratio (94.2±0.91 %), and selectivity (98.6 %±0.55 %). The current work develops an effective strategy for integrating the active site construction into realistic reactions, providing new opportunities for Cu-based chemistry and catalysis sciences research.

Ni-Fe/Co-Fe Oxide-MoSe2 Hybrid Nanostructures as Novel Electrocatalysts for High-Performance Rechargeable Zinc-Air Batteries

Metal-air batteries can play a crucial role in curbing air pollution due to carbon emission. Here, we report the hydrothermally synthesized bimetal oxides (NiFe2O4 and CoFe2O4) and their hybrid nanostructures with MoSe2 as potential electrocatalysts for electrically rechargeable Zn-air batteries. The NiFe2O4-MoSe2 hybrid nanostructure exhibits the best electrocatalytic activity (overpotential η10 ≈ 218 mV and Tafel slope ≈ 37 mV dec-1) for the OER study among prepared electrocatalysts in 1 M KOH electrolyte. Among the designed rechargeable Zn-air batteries, hybrid nanostructure-based batteries show superior performance, with the NiFe2O4-MoSe2 based device showing the best performance, having a high open-circuit voltage of ∼1.43 V, a peak power density of ∼176 mW cm-2, a specific capacity of ∼1025 mAh gZn-1, and an energy density of ∼1205 Wh kgZn-1. The superior performance of the hybrid nanostructures is due to the synergistic effect between MoSe2 and bimetal oxides, which enhances the conductivity, oxygen mobility, and active sites of the catalysts.

Engineering organic polymers as emerging sustainable materials for powerful electrocatalysts

Cost-effective and high-efficiency catalysts play a central role in various sustainable electrochemical energy conversion technologies that are being developed to generate clean energy while reducing carbon emissions, such as fuel cells, metal-air batteries, water electrolyzers, and carbon dioxide conversion. In this context, a recent climax in the exploitation of advanced earth-abundant catalysts has been witnessed for diverse electrochemical reactions involved in the above mentioned sustainable pathways. In particular, polymer catalysts have garnered considerable interest and achieved substantial progress very recently, mainly owing to their pyrolysis-free synthesis, highly tunable molecular composition and microarchitecture, readily adjustable electrical conductivity, and high stability. In this review, we present a timely and comprehensive overview of the latest advances in organic polymers as emerging materials for powerful electrocatalysts. First, we present the general principles for the design of polymer catalysts in terms of catalytic activity, electrical conductivity, mass transfer, and stability. Then, the state-of-the-art engineering strategies to tailor the polymer catalysts at both molecular (i.e., heteroatom and metal atom engineering) and macromolecular (i.e., chain, topology, and composition engineering) levels are introduced. Particular attention is paid to the insightful understanding of structure-performance correlations and electrocatalytic mechanisms. The fundamentals behind these critical electrochemical reactions, including the oxygen reduction reaction, hydrogen evolution reaction, CO2 reduction reaction, oxygen evolution reaction, and hydrogen oxidation reaction, as well as breakthroughs in polymer catalysts, are outlined as well. Finally, we further discuss the current challenges and suggest new opportunities for the rational design of advanced polymer catalysts. By presenting the progress, engineering strategies, insightful understandings, challenges, and perspectives, we hope this review can provide valuable guidelines for the future development of polymer catalysts.

Surface-Reconstructed Ru-Doped Nickel/Iron Oxyhydroxide Arrays for Efficient Oxygen Evolution

The generation of an active phase through dynamic surface reconstruction is a promising strategy for improving the activity of electrocatalysts. However, studies investigating the reconstruction process and its impact on the intrinsic properties of the catalysts are scarce. Herein, the surface reconstruction of NiFe2 O4 interfaced with NiMoO4 (Ru-NFO/NMO) facilitated by Ru doping is reported. The electrochemical and material characterizations demonstrate that Ru doping can regulate the electronic structure of NFO/NMO and induce the high-valence state of Ni3.6+ δ , facilitating the surface reconstruction to highly active Ru-doped NiFeOOH/NiOOH (SR-Ru-NFO/NMO). The optimized SR-Ru-NFO/NMO exhibits promising performance in the oxygen evolution reaction, displaying a low overpotential of 229 mV at 10 mA cm-2 and good stability at varying current densities for 80 h. Density functional theory calculations indicate that Ru doping can increase the electron density and optimize intermediate adsorption by shifting the d-band center downward. This work provides valuable insights into the tuning of electrocatalysts by surface reconstruction and offers a rational design strategy for the development of highly active oxygen evolution reaction electrocatalysts.

The ionic liquids upon perchlorate to promote the C-C/C-O bonds cleavage in alkali lignin under photothermal synergism

Transforming lignin into aromatic monomers is critically attractive to develop green and sustainable energy supplies. However, the usage of the additional catalysts like metal or base/acid is commonly limited by the caused repolymerized and environmental issues. The key step is to mediate electron transfer in lignin to trigger lignin C-C/C-O bonds cleavage without the catalysts mentioned above. Here, we report that the ionic liquids [BMim][ClO4] was found to trigger lignin electron transfer to cleave the C-C/C-O bonds for aromatic monomers without any additional catalyst. The proton transfer from [BMim]+ to [ClO4]- could polarize the anion and decrease its structure stability, upon which the active hydroxyl radical generated and induced lignin C-C/C-O bonds fragmentation via free radical-mediated routes with the assistance of photothermal synergism. About 4.4 wt% yields of aromatic monomers, mainly composed of vanillin and acetosyringone, are afforded in [BMim][ClO4] under UV-light irradiation in the air at 80 °C. This work opens the way to produce value-added aromatic monomers from lignin using an eco-friendly, energy-efficient, and simple route that may contribute to the sustainable utilization of renewable natural resources.

Water activating fresh NiMo foam for enhanced urea electrolysis

Recently, production of hydrogen (H2) through the urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) has acquired great attention because it is more environmentally friendly and energy-saving. Herein, an approach of water activation was developed for in situ growth of NiMo LDH nanosheet arrays on NiMo foam without using any binder or pressurizing or heating steps. The obtained NiMo foam electrodes showed exceptional catalytic activity and durability for both the UOR and HER. This work offers a new standpoint on designing electrodes with high activation for efficient and sustainable hydrogen production coupled with urea organic oxidation.

A Mild Hyperthermia Hollow Carbon Nanozyme as Pyroptosis Inducer for Boosted Antitumor Immunity

The immune checkpoint blockade (ICB) antibody immunotherapy has demonstrated clinical benefits for multiple cancers. However, the efficacy of immunotherapy in tumors is suppressed by deficient tumor immunogenicity and immunosuppressive tumor microenvironments. Pyroptosis, a form of programmed cell death, can release tumor antigens, activate effective tumor immunogenicity, and improve the efficiency of ICB, but efficient pyroptosis for tumor treatment is currently limited. Herein, we show a mild hyperthermia-enhanced pyroptosis-mediated immunotherapy based on hollow carbon nanozyme, which can specifically amplify oxidative stress-triggered pyroptosis and synchronously magnify pyroptosis-mediated anticancer responses in the tumor microenvironment. The hollow carbon sphere modified with iron and copper atoms (HCS-FeCu) with multiple enzyme-mimicking activities has been engineered to induce cell pyroptosis via the radical oxygen species (ROS)-Tom20-Bax-Caspase 3-gasdermin E (GSDME) signaling pathway under light activation. Both in vitro and in vivo antineoplastic results confirm the superiority of HCS-FeCu nanozyme-induced pyroptosis. Moreover, the mild photothermal-activated pyroptosis combining anti-PD-1 can enhance antitumor immunotherapy. Theoretical calculations further indicate that the mild photothermal stimulation generates high-energy electrons and enhances the interaction between the HCS-FeCu surface and adsorbed oxygen, facilitating molecular oxygen activation, which improves the ROS production efficiency. This work presents an approach that effectively transforms immunologically "cold" tumors into "hot" ones, with significant implications for clinical immunotherapy.

Enhanced Electrocatalytic Water Oxidation by Interfacial Phase Transition and Photothermal Effect in Multiply Heterostructured Co9 S8 /Co3 S4 /Cu2 S Nanohybrids

The rational design of advanced nanohybrids (NHs) with optimized interface electronic environment and rapid reaction kinetics is pivotal to electrocatalytic schedule. Herein, we developed a multiple heterogeneous Co9 S8 /Co3 S4 /Cu2 S nanoparticle in which Co3 S4 germinates between Co9 S8 and Cu2 S. Using high-angle annular-dark-field imaging and theoretical calculation, it was found that the integration of Co9 S8 and Cu2 S tends to trigger the interface phase transition of Co9 S8 , leading to Co3 S4 interlayer due to the low formation energy of Co3 S4 /Cu2 S (-7.61 eV) than Co9 S8 /Cu2 S (-5.86 eV). Such phase transition not only lowers the energy barrier of oxygen evolution reaction (OER, from 0.335 eV to 0.297 eV), but also increases charge carrier density (from 7.76×1014 to 2.09×1015  cm-3 ), and creates more active sites. Compared to Co9 S8 and Cu2 S, the Co9 S8 /Co3 S4 /Cu2 S NHs also demonstrate notable photothermal effect that can heat the catalyst locally, offset the endothermic enthalpy change of OER, and promote carrier migrate, reaction intermediates adsorption/deprotonation to improve reaction kinetics. Profiting from these favorable factors, the Co9 S8 /Co3 S4 /Cu2 S catalyst only requires an OER overpotential of 181 mV and overall water splitting cell voltage of 1.43 V to driven 10 mA cm-2 under the irradiation of near-infrared light, outperforming those without light irradiation and many reported Co-based catalysts.

Integrated Photochromic-Photothermal Processes for Catalytic Plastic Upcycling

Incorporating high-energy ultraviolet (UV) photons into photothermal catalytic processes may enable photothermal-photochemical synergistic catalysis, which represents a transformative technology for waste plastic recycling. The major challenge is avoiding side reactions and by-products caused by these energetic photons. Here, we break through the limitation of the existing photothermal conversion mechanism and propose a photochromic-photothermal catalytic system based on polyol-ligated TiO2 nanocrystals. Upon UV or sunlight irradiation, the chemically bonded polyols can rapidly capture holes generated by TiO2 , enabling photogenerated electrons to reduce Ti4+ to Ti3+ and produce oxygen vacancies. The resulting abundant defect energy levels boost sunlight-to-heat conversion efficiency, and simultaneously the oxygen vacancies facilitate polyester glycolysis by activating the nucleophilic addition-elimination process. As a result, compared to commercial TiO2 (P25), we achieve 6-fold and 12.2-fold performance enhancements under thermal and photothermal conditions, respectively, while maintaining high selectivity to high-valued monomers. This paradigm-shift strategy directs energetic UV photons for activating catalysts and avoids their interaction with reactants, opening the possibility of substantially elevating the efficiency of more solar-driven catalysis.

Facile deposition of FeNi/Ni hybrid nanoflower electrocatalysts for effective and sustained water oxidation

Bimetallic iron-nickel (FeNi) compounds are widely studied materials for the oxygen evolution reaction (OER) owing to their high electrocatalytic performance and low cost. In this work, we produced thin films of the FeNi alloy on nickel foam (NF) by using an aerosol-assisted chemical deposition (AACVD) method and examined their OER catalytic activity. The hybrid FeNi/Ni catalysts obtained after 1 and 2 h of AACVD deposition show improved charge transfer and kinetics for the OER due to the strong interface between the FeNi alloy and Ni support. The FeNi/Ni-2h catalyst has higher catalytic activity than the FeNi/Ni-1h catalyst because of its nanoflower morphology that provides a large surface area and numerous active sites for the OER. Therefore, the FeNi/Ni-2h catalyst exhibits low overpotentials of 300 and 340 mV at 50 and 500 mA cm-2 respectively, and excellent stability over 100 h, and ∼0% loss after 5000 cycles in 1 M KOH electrolyte. Furthermore, this catalyst has a small Tafel slope, low charge transfer resistance and high current exchange density and thus surpasses the benchmark IrO2 catalyst. The easy, simple, and scalable AACVD method is an effective way to develop thin film electrocatalysts with high activity and stability.

Enhanced Oxygen Evolution Reaction Performance on NiSx@Co3O4/Nickel Foam Electrocatalysts with Their Photothermal Property

Based on the principle of heterogeneous catalysis for water electrolysis, electrocatalysts with appropriate electronic structure and photothermal property are expected to drive the oxygen evolution reaction effectively. Herein, amorphous NiS_x-coupled nanourchin-like Co₃O₄ was prepared on nickel foam (NiS_x@Co₃O₄/NF) and investigated as a electrocatalyst for photothermal-assisted oxygen evolution reaction. The experimental investigations and simulant calculations jointly revealed NiS_x@Co₃O₄/NF to be of suitable electronic structure and high near-infrared photothermal conversion capability to achieve the oxygen evolution reaction advantageously both in thermodynamics and in kinetics. Relative to Co₃O₄/NF and NiS_x/NF, better oxygen evolution reaction activity, kinetics, and stability were achieved on NiS_x@Co₃O₄/NF in 1.0 M KOH owing to the NiS_x/Co₃O₄ synergetic effect. In addition, the oxygen evolution reaction performance of NiS_x@Co₃O₄/NF can be obviously enhanced under near-infrared light irradiation, since NiS_x@Co₃O₄ can absorb the near-infrared light to produce electric and thermal field. For the photothermal-mediated oxygen evolution reaction, the overpotential and Tafel slope of NiS_x@Co₃O₄/NF at 50 mA cm^-2 were reduced by 23 mV and 13 mV/dec, respectively. The present work provides an inspiring reference to design and develop photothermal-assisted water electrolysis using abundant solar energy.

Transforming NiCo2O4 nanorods into nanoparticles using citrus lemon juice enhancing electrochemical properties for asymmetric supercapacitor and water oxidation

Recently, the nanostructured nickel-cobalt bimetallic oxide (NiCo₂O₄) material with high electrochemical activity has received intensive attention. Beside this, the biomass assisted synthesis of NiCo₂O₄ is gaining popularity due to its advantageous features such as being low cost, simplicity, minimal use of toxic chemicals, and environment-friendly and ecofriendly nature. The electrochemical activity of spinel NiCo₂O₄ is associated with its mixed metal oxidation states. Therefore, much attention has been paid to the crystal quality, morphology and tunable surface chemistry of NiCo₂O₄ nanostructures. In this study, we have used citrus lemon juice consisting of a variety of chemical compounds having the properties of a stabilizing agent, capping agent and chelating agent. Moreover, the presence of several acidic chemical compounds in citrus lemon juice changed the pH of the growth solution and consequently we observed surface modified and structural changes that were found to be very effective for the development of energy conversion and energy storage systems. These naturally occurring compounds in citrus lemon juice played a dynamic role in transforming the nanorod morphology of NiCo₂O₄ into small and well-packed nanoparticles. Hence, the prepared NiCo₂O₄ nanostructures exhibited a new surface-oriented nanoparticle morphology, high concentration of defects on the surface (especially oxygen vacancies), sufficient ionic diffusion and reaction of electrolytic ions, enhanced electrical conductivity, and favorable reaction kinetics at the interface. The electrocatalytic properties of the NiCo₂O₄ nanostructures were studied in oxygen evolution reaction (OER) at a low overpotential of 250 mV for 10 mA cm^-2, Tafel slope of 98 mV dec^-1, and durability of 40 h. Moreover, an asymmetric supercapacitor was produced and the obtained results indicated a high specific capacitance of (C_s) of 1519.19 F g^-1, and energy density of 33.08 W h kg^-1 at 0.8 A g^-1. The enhanced electrochemical performance could be attributed to the favorable structural changes, surface modification, and surface crystal facet exposure due to the use of citrus lemon juice. The proposed method of transformation of nanorod to nanoparticles could be used for the design of a new generation of efficient electrocatalyst materials for energy storage and conversion uses.

Room-temperature self-healing polyurethane-cellulose nanocrystal composites with strong strength and toughness based on dynamic bonds

Self-healing materials suffer from a trade-off relationship between their self-healing ability and mechanical strength, which limits their applications. Therefore, we developed a room-temperature self-healing supramolecular composite based on polyurethane (PU) elastomer, cellulose nanocrystals (CNCs), and multiple dynamic bonds. In this system, the abundant hydroxyl groups on the surfaces of the CNCs form multiple hydrogen bonds with the PU elastomer, yielding a dynamic physical cross-linking network. This dynamic network enables self-healing without degrading the mechanical properties. As a result, the obtained supramolecular composites exhibited high tensile strength (24.5 ± 2.3 MPa), good elongation at break (1484.8 ± 74.9 %), favourable toughness (156.4 ± 31.1 MJ m^-3, which is equivalent to that of spider silk and 5.1-times higher than that of aluminium), and excellent self-healing efficiency (95 ± 1.9 %). Notably, the mechanical properties of the supramolecular composites were almost completely retained after reprocessing three times. Further, using these composites, flexible electronic sensors were prepared and tested. In summary, we have reported a method for preparing supramolecular materials having high toughness and room temperature self-healing ability that have applications in flexible electronics.

Promoting the electrocatalytic oxygen evolution reaction on NiCo2O4 with infrared-thermal effect: A strategy to utilize the infrared solar energy to reduce activation energy during water splitting

Utilization of the infrared (IR) solar energy remains a challenging task for traditional photo(electro)catalysis. Taking advantage of the IR-thermal effect to facilitate sluggish electrocatalytic reactions emerges as a promising way to utilize the IR band of the solar spectrum. In this work, nickel foam (NF) supported NiCo₂O₄ nanoneedles (NF/NiCo₂O₄ NNs) were prepared to promote the oxygen evolution reaction (OER) via the IR-thermal effect, with the NF/NiCo₂O₄ NNs acting as both the IR absorbing antennae and the OER active anode. The potential required to deliver a current density of 200 mA cm^-2 is negatively shifted from 1.618 V in the dark to 1.578 V under IR irradiation, and the Tafel slope is also decreased from 106 to 89 mV dec^-1. We demonstrate that the enhancement of OER activity is due to the localized temperature rise under IR irradiation. We measured the electrochemical activation energy of OER on NF/NiCo₂O₄ with and without IR irradiation, and the results reveal that IR irradiation reduces the kinetic energy barrier of the OER by IR-thermal effect and then facilitates OER kinetics. This work highlights a new approach to utilizing the IR portion of the sunlight to produce renewable hydrogen energy via water splitting.

Ir-CoO Active Centers Supported on Porous Al2 O3 Nanosheets as Efficient and Durable Photo-Thermal Catalysts for CO2 Conversion

Photo-thermal catalytic CO₂ hydrogenation is currently extensively studied as one of the most promising approaches for the conversion of CO₂ into value-added chemicals under mild conditions; however, achieving desirable conversion efficiency and target product selectivity remains challenging. Herein, the fabrication of Ir-CoO/Al₂ O₃ catalysts derived from Ir/CoAl LDH composites is reported for photo-thermal CO₂ methanation, which consist of Ir-CoO ensembles as active centers that are evenly anchored on amorphous Al₂ O₃ nanosheets. A CH₄ production rate of 128.9 mmol g_cat⁻ ¹ h⁻¹  is achieved at 250 °C under ambient pressure and visible light irradiation, outperforming most reported metal-based catalysts. Mechanism studies based on density functional theory (DFT) calculations and numerical simulations reveal that the CoO nanoparticles function as photocatalysts to donate electrons for Ir nanoparticles and meanwhile act as "nanoheaters" to effectively elevate the local temperature around Ir active sites, thus promoting the adsorption, activation, and conversion of reactant molecules. In situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) demonstrates that illumination also efficiently boosts the conversion of formate intermediates. The mechanism of dual functions of photothermal semiconductors as photocatalysts for electron donation and as nano-heaters for local temperature enhancement provides new insight in the exploration for efficient photo-thermal catalysts.

Superwettable and photothermal all-in-one electrocatalyst for boosting water/urea electrolysis

Developing multifunctional all-in-one electrocatalysts for energy-saving hydrogen generation remains a challenge. In this study, a simple and feasible thermal phosphorization strategy is explored to rationally construct P-doped MoO₂-NiMoO₄ heterostructure on nickel foam (NF). The heterointerfaced P-MoO₂-NiMoO₄/NF can simultaneously realize the integrated all-in-one functionalities, innovatively introducing superwettable surfaces, photothermal conversion capabilities and electrocatalytic functions. The superwettability gives P-MoO₂-NiMoO₄/NF sufficient electrolyte permeation and smooth bubble detachment. The plasmonic MoO₂ with photothermal performance greatly elevates the local surface temperature of in P-MoO₂-NiMoO₄/NF, which is conducive to improve the electrocatalytic efficiency. The favorable in-situ surface reconstruction brings abundant active sites for electrocatalytic reactions. As an advanced multifunctional electrocatalyst, the superwettable and photothermal P-MoO₂-NiMoO₄/NF exhibits significantly improved performances in oxygen evolution reaction (OER) and urea oxidation reaction (UOR). More importantly, the highly efficient and stable overall water-urea electrolysis assisted by photothermal fields can be simply achieved by exposing P-MoO₂-NiMoO₄/NF to near-infrared (NIR) light.

Oxygen Evolution/Reduction Reaction Catalysts: From In Situ Monitoring and Reaction Mechanisms to Rational Design

The oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are core steps of various energy conversion and storage systems. However, their sluggish reaction kinetics, i.e., the demanding multielectron transfer processes, still render OER/ORR catalysts less efficient for practical applications. Moreover, the complexity of the catalyst-electrolyte interface makes a comprehensive understanding of the intrinsic OER/ORR mechanisms challenging. Fortunately, recent advances of in situ/operando characterization techniques have facilitated the kinetic monitoring of catalysts under reaction conditions. Here we provide selected highlights of recent in situ/operando mechanistic studies of OER/ORR catalysts with the main emphasis placed on heterogeneous systems (primarily discussing first-row transition metals which operate under basic conditions), followed by a brief outlook on molecular catalysts. Key sections in this review are focused on determination of the true active species, identification of the active sites, and monitoring of the reactive intermediates. For in-depth insights into the above factors, a short overview of the metrics for accurate characterizations of OER/ORR catalysts is provided. A combination of the obtained time-resolved reaction information and reliable activity data will then guide the rational design of new catalysts. Strategies such as optimizing the restructuring process as well as overcoming the adsorption-energy scaling relations will be discussed. Finally, pending current challenges and prospects toward the understanding and development of efficient heterogeneous catalysts and selected homogeneous catalysts are presented.

Synthesis of Hollow Leaf-Shaped Iron-Doped Nickel–Cobalt Layered Double Hydroxides Using Two-Dimensional (2D) Zeolitic Imidazolate Framework Catalyzing Oxygen Evolution Reaction

Layered double hydroxides (LDHs) have been reported as one of the most effective materials for oxygen evolution reaction (OER) catalysts, which are prone to hydrolysis and oxidation under OER conditions. Metal–organic frameworks (MOFs) are porous materials with high crystallinity and internal surface area. The design of LDHs based on MOFs has attracted increasing attention owing to their high surface area, exposed catalysis sites, and fast charge/mass transport kinetics. Herein, we report a novel approach to fabricate a leaf-shaped iron-doped nickel–cobalt LDH (L-Fe-NiCoLDH) derived from a two-dimensional (2D) zeolitic imidazolate framework with a leaf-like morphology (ZIFL). Iron doping played a significant role in enhancing the specific surface area, affecting the OER performance. L-Fe-NiCoLDH showed high OER performance with an overpotential of 243 mV at 10 mA cm−2 and high durability after 20 h. The design of LDHs based on the leaf morphology of MOFs offers tremendous potential for improving OER efficiency.

Sulfate-Decorated Amorphous-Crystalline Cobalt-Iron Oxide Nanosheets to Enhance O-O Coupling in the Oxygen Evolution Reaction

The electrochemical oxygen evolution reaction (OER) plays a fundamental role in several energy technologies, which performance and cost-effectiveness are in large part related to the used OER electrocatalyst. Herein, we detail the synthesis of cobalt-iron oxide nanosheets containing controlled amounts of well-anchored SO₄^2- anionic groups (CoFe_xO_y-SO₄). We use a cobalt-based zeolitic imidazolate framework (ZIF-67) as the structural template and a cobalt source and Mohr's salt ((NH₄)₂Fe(SO₄)₂·6H₂O) as the source of iron and sulfate. When combining the ZIF-67 with ammonium iron sulfate, the protons produced by the ammonium ion hydrolysis (NH₄⁺ + H₂O = NH₃·H₂O + H⁺) etch the ZIF-67, dissociating its polyhedron structure, and form porous assemblies of two-dimensional nanostructures through a diffusion-controlled process. At the same time, iron ions partially replace cobalt within the structure, and SO₄^2- ions are anchored on the material surface by exchange with organic ligands. As a result, ultrathin CoFe_xO_y-SO₄ nanosheets are obtained. The proposed synthetic procedure enables controlling the amount of Fe and SO₄ ions and analyzing the effect of each element on the electrocatalytic activity. The optimized CoFe_xO_y-SO₄ material displays outstanding OER activity with a 10 mA cm^-2 overpotential of 268 mV, a Tafel slope of 46.5 mV dec^-1, and excellent stability during 62 h. This excellent performance is correlated to the material's structural and chemical parameters. The assembled nanosheet structure is characterized by a large electrochemically active surface area, a high density of reaction sites, and fast electron transportation. Meanwhile, the introduction of iron increases the electrical conductivity of the catalysts and provides fast reaction sites with optimum bond energy and spin state for the adsorption of OER intermediates. The presence of sulfate ions at the catalyst surface modifies the electronic energy level of active sites, regulates the adsorption of intermediates to reduce the OER overpotential, and promotes the surface charge transfer, which accelerates the formation of oxygenated intermediates. Overall, the present work details the synthesis of a high-efficiency OER electrocatalyst and demonstrates the introduction of nonmetallic anionic groups as an excellent strategy to promote electrocatalytic activity in energy conversion technologies.

In Situ Anodic Oxidation Tuning of NiFeV Diselenide to the Core-Shell Heterojunction for Boosting Oxygen Evolution

Developing non-noble metal-based core-shell heterojunction electrocatalysts with high catalytic activity and long-lasting stability is crucial for the oxygen evolution reaction (OER). Here, we prepared novel core-shell Fe,V-NiSe₂@NiFe(OH)_x heterostructured nanoparticles on hydrophilic-treated carbon paper with high electronic transport and large surface area for accelerating the oxygen evolution rate via high-temperature selenization and electrochemical anodic oxidation procedures. Performance testing shows that Fe,V-NiSe₂@NiFe(OH)_x possesses the highest performance for OER compared to as-prepared diselenide core-derived heterojunctions, which only require an overpotential of 243 mV at 10 mA cm^-2 and a low Tafel slope of 91.6 mV decade^-1 under basic conditions. Furthermore, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) confirm the morphology and elementary stabilities of Fe,V-NiSe₂@NiFe(OH)_x after long-term chronopotentiometric testing. These advantages are largely because of the strong synergistic effect between the Fe,V-NiSe₂ core with high conductivity and the amorphous NiFe(OH)_x shell with enriched defects and vacancies. This study also presents a general approach to designing and synthesizing more active core-shell heterojunction electrocatalysts for OER.

Electron delocalization triggers nonradical Fenton-like catalysis over spinel oxides

Nonradical Fenton-like catalysis offers opportunities to overcome the low efficiency and secondary pollution limitations of existing advanced oxidation decontamination technologies, but realizing this on transition metal spinel oxide catalysts remains challenging due to insufficient understanding of their catalytic mechanisms. Here, we explore the origins of catalytic selectivity of Fe-Mn spinel oxide and identify electron delocalization of the surface metal active site as the key driver of its nonradical catalysis. Through fine-tuning the crystal geometry to trigger Fe-Mn superexchange interaction at the spinel octahedra, ZnFeMnO₄ with high-degree electron delocalization of the Mn-O unit was created to enable near 100% nonradical activation of peroxymonosulfate (PMS) at unprecedented utilization efficiency. The resulting surface-bound PMS* complex can efficiently oxidize electron-rich pollutants with extraordinary degradation activity, selectivity, and good environmental robustness to favor water decontamination applications. Our work provides a molecule-level understanding of the catalytic selectivity and bimetallic interactions of Fe-Mn spinel oxides, which may guide the design of low-cost spinel oxides for more selective and efficient decontamination applications.

Rational coordination regulation in carbon-based single-metal-atom catalysts for electrocatalytic oxygen reduction reaction

Single-metal-atom catalysts (SMACs) have garnered extensive attention for various electrocatalytic applications, owing to their maximum atom-utilization efficiency, tunable electronic structure, and remarkable catalytic performance. In particular, carbon-based SMACs exhibit optimal electrocatalytic activity for the oxygen reduction reaction (ORR) which is of paramount importance for several sustainable energy conversion and generation technologies, such as fuel cells and metal-air batteries. Despite continuous endeavors in developing various advanced carbon-based SMACs for electrocatalytic ORR, the rational regulation of coordination structure and thus the electronic structure of carbon-based SMACs remains challenging. In this review, we critically examine the role of coordination structure, including local coordination structure (i.e., metal atomic centers and the first coordination shell) and extended local coordination structure (i.e., the second and higher coordination shells), on the rational design of carbon-based SMACs for high-efficiency electrocatalytic ORR. Insights into the relevance between coordination structures and their intrinsic ORR activities are emphatically exemplified and discussed. Finally, we also propose the major challenges and future perspectives in the rational design of advanced carbon-based SMACs for electrocatalytic ORR. This review aims to emphasize the significance of coordination structure and deepen the insightful understanding of structure-performance relationships.

Ultrafast Preparation of Nonequilibrium FeNi Spinels by Magnetic Induction Heating for Unprecedented Oxygen Evolution Electrocatalysis

Carbon-supported nanocomposites are attracting particular attention as high-performance, low-cost electrocatalysts for electrochemical water splitting. These are mostly prepared by pyrolysis and hydrothermal procedures that are time-consuming (from hours to days) and typically difficult to produce a nonequilibrium phase. Herein, for the first time ever, we exploit magnetic induction heating-quenching for ultrafast production of carbon-FeNi spinel oxide nanocomposites (within seconds), which exhibit an unprecedentedly high performance towards oxygen evolution reaction (OER), with an ultralow overpotential of only +260 mV to reach the high current density of 100 mA cm⁻². Experimental and theoretical studies show that the rapid heating and quenching process (ca. 10³ K s⁻¹) impedes the Ni and Fe phase segregation and produces a Cl-rich surface, both contributing to the remarkable catalytic activity. Results from this study highlight the unique advantage of ultrafast heating/quenching in the structural engineering of functional nanocomposites to achieve high electrocatalytic performance towards important electrochemical reactions.

Correlating the effect of preparation methods on the structural and magnetic properties, and reducibility of CuFe2O4 catalysts

CuFe2O4 spinel oxide has attracted research interest because of its versatile practical applications, especially for catalysis. In this study, nanometre-sized CuFe2O4 particles were prepared by three different methods, including nanospace confinement in SBA-15, hard template removal, and sol-gel combustion. The relationship between structure, size, magnetic behaviour, and reducibility of the catalysts was further investigated by various advanced techniques. Samples prepared by impregnation and hard template removal show high surface area and small crystallite size with superparamagnetic behaviour. In contrast, the sol-gel sample exhibits ferromagnetic properties with a large crystallite size and low surface area. Although all samples present a tetragonal crystal structure, the distributions of Fe and Cu cations in tetrahedral and octahedral sites in the spinel structure are different. The reducibility results demonstrate that the supported CuFe2O4/SBA-15 shows the lowest reduction profile. These results could suggest that the synthesis method strongly affects the crystal properties and cation distribution in the spinel structure, microstructure, surface area and reducibility, which are among the most relevant physicochemical properties for the catalytic activity.