Insights into the activity of nickel boride/nickel heterostructures for efficient methanol electrooxidation

Vanadium-Modulated Molybdenum/Nickel-Based Multi-Heterostructures finely tailoring d-Band centers for electrocatalytic water splitting

Finely tailoring the d-band centers (εd) of various metals is expected to balance the adsorption/desorption of multiple intermediates for water electrolysis, but remains challenging. Herein, porous ultrathin nanosheets consisting of V-doped Mo/Ni-based multi-heterostructures (V-MoN/NixNy) are designed as bifunctional electrocatalysts for hydrogen and oxygen evolution reaction (HER/OER). V-substituted Mo-based polyoxometalates (POMs) were assembled with Ni(OH)2 to target multi-interface coupled Mo/Ni-based heterojunctions and precise V-doping. Theoretical calculations validate that V doping and heterostructure cause electron accumulation on the V-MoN side, which induces an upward shift in εd (Mo), strengthening H2O adsorption. New active sites (V) and the nearby N sites are responsible for *OH and H* adsorption, thereby improving HER performance. After forming heterostructure, ɛd (Ni) shifts upward and significantly enhances the adsorption of various key intermediates (OH*, O* and OOH*). While, V-doping renders ɛd (Ni) slightly shift downward, which largely weakens the O* adsorption. The elaborate customizing of εd (Ni) effectively promotes the transition of O* to OOH*, thereby improving OER activity. Impressively, V-MoN/NixNy manifests excellent activity, with overpotentials of 193 mV (HER) and 460 mV (OER) at 400 mA cm-2, significantly outperforming commercial Pt/C (306 mV) and RuO2 (512 mV). The assembled electrolyzer requires only 1.504 V@10 mA cm-2 for overall water splitting with good durability. This study underscores the superiority of finely tailoring εd in triggering multi-site synergism.

High loading of atomically exposed edge nickel sites embedded in hollow porous carbon nanofibers for enhanced methanol electrooxidation in direct methanol fuel cells

The enhancement of catalytic activity and durability for atomically dispersed metal-nitrogen-carbon (M-N-C) catalysts in methanol oxidation reaction (MOR) anodes within direct methanol fuel cells presents a significant challenge. Here, we developed hollow porous nanofiber catalysts featuring edge Ni-N4 atomic sites through coaxial electrostatic spinning with domain-restricted Ni atoms embedded within a zeolitic imidazolium ester backbone, thereby increasing the exposure of accessible active sites (Ni: 4.96 %). The distinctive hollow porous fiber morphology and hierarchical structure facilitate convenient electronic conductivity and mass transport of reactants. Theoretical findings indicate that the surface adsorption of methanol at the edge Ni-N4 atomic sites exhibits negative free energy, promoting the adsorption and activation of reactants. Furthermore, the initial dehydrogenation step demonstrates a low free energy change, favoring reaction kinetics. The membrane electrode assembly achieved a power density of 42.2 mW cm-2 in single-cell application tests while displaying improved durability. This research provides valuable insights for future advancements in single-atom catalyst development for fuel cells or other energy applications.

Geography-guided industrial-level upcycling of polyethylene terephthalate plastics through alkaline seawater-based processes

The escalating plastic crisis can be mitigated by upgrading waste polyethylene terephthalate (PET). Leveraging the geographical advantages of offshores with established chlor-alkali industries, abundant renewable energy, and extensive seawater, we here present a technically and economically viable strategy of harnessing natural seawater as a medium to transform PET plastics into high-value chemicals. We report a nickel-molybdenum catalyst incorporating frustrated Lewis pairs for the efficient breakage of C─C bond and the oxidation of ethylene glycol, which sustains a current of 6 amperes at 1.74 volts over 350 hours, with a projected revenue of approximately $304 United States dollar (USD) per ton of processed PET plastics. In a customized electrolyzer, we successfully convert 301.0 grams of waste PET into 227.1 grams of p-phthalic acid (95.5% yield), 1486.2 grams of potassium diformate (67.2% yield), and approximately 214.9 liters of green hydrogen. This study paves the way for scalable PET upcycling, contributing to a circular economy and mitigating the plastic pollution crisis.

Bioinspired Dual-Site Photocathode with Atomic Molybdenum and Alkynyl Networks for Scalable Solar Ammonia Synthesis

The Haber-Bosch process, while pivotal for global ammonia production, remains energy-intensive and environmentally unsustainable. Here, we report a nitrogenase-inspired photocathode (Mo1/HsGDY@Cu2O) that synergistically integrates light-harvesting Cu2O nanowires, hydrogen-radical-generating alkynyl-rich graphdiyne (HsGDY), and atomically dispersed molybdenum sites for solar-driven nitrogen fixation. Mimicking the Fe/MoFe-cofactor collaboration in nitrogenase, the photocathode enables efficient N2 adsorption at Mo1 sites and hydrogen radical transfer from adjacent alkynyl groups, significantly lowering the energy barrier for N2 hydrogenation. Under 10-sun illumination, the system achieves a record ammonia yield of 78.9 μg cm-2 h-1 with a Faradaic efficiency of 38.9% while maintaining 86% activity over 240 h. The ammonia solution directly enhances Epipremnum aureum root growth by 2.3-fold, demonstrating immediate agricultural utility. Combined with bias-free operation and scalable solar concentration, this work provides a practical blueprint for decarbonizing fertilizer production. Operando spectroscopy and DFT calculations further reveal that the dual-site synergy─Mo1 for N2 activation and alkynyl groups for H• supply─drives the catalytic mechanism, offering a universal strategy for enzyme-inspired energy conversion systems.

Coupling Value-Added Methanol Oxidation with CO2 Electrolysis by Low-Coordinated Atomic Ni Sites

The combination of CO2 fixation and small organic molecule oxidation offers a promising solution to increasing severe environmental issues and energy crises. Here, low-coordinated NiN3 sites were anchored onto nitrogen-doped ordered mesoporous carbon (Ni-SAs/NOMC), which is capable of efficiently catalyzing the coupled methanol oxidation reaction and CO2 reduction reaction (MOR||CO2RR), thereby reducing the energy required for CO2 conversion and enhancing the economic value of the CO2 electrolytic system. In the membrane electrode assembly electrolyzer-based MOR||CO2RR, Ni-SAs/NOMC achieved Faradaic efficiencies (FEs) of 95.4% for formate at the anode and 96.3% for CO at the cathode. Moreover, at a current density of 0.8 A cm-2, Ni-SAs/NOMC demonstrated stable electrolysis for up to 100 h, with FEs at both the anode and cathode remaining stable at approximately 90%. In situ spectroscopy analyses and theoretical calculations identified the formation of critical intermediate species and the origin of activity improvement, guiding the development of efficient electrosynthesis of valuable chemicals.

Electrochemical Hydrogen Production Coupling with the Upgrading of Organic and Inorganic Chemicals

Electrocatalytic water splitting powered by renewable energy is a green and sustainable method for producing high-purity H2. However, in conventional water electrolysis, the anodic oxygen evolution reaction (OER) involves a four-electron transfer process with inherently sluggish kinetics, which severely limits the overall efficiency of water splitting. Recently, replacing OER with thermodynamically favorable oxidation reactions, coupled with the hydrogen evolution reaction, has garnered significant attention and achieved remarkable progress. This strategy not only offers a promising route for energy-saving H₂ production but also enables the simultaneous synthesis of high-value-added products or the removal of pollutants at the anode. Researchers successfully demonstrate the upgrading of numerous organic and inorganic alternatives through this approach. In this review, the latest advances in the coupling of electrocatalytic H2 production and the upgrading of organic and inorganic alternative chemicals are summarized. What's more, the optimization strategy of catalysts, structure-performance relationship, and catalytic mechanism of various reactions are well discussed in each part. Finally, the current challenges and future prospects in this field are outlined, aiming to inspire further innovative breakthroughs in this exciting area of research.

Constructing nanoneedle arrays of heterostructured RuO2-Co3O4 with tip-effect-induced enrichment of reactants for enhanced water oxidation

Nanoneedle arrays of heterostructured RuO2-Co3O4 electrocatalysts were constructed, showing improved water oxidation activity and durable stability. The synergy of tip-effect-induced OH- enrichment, superior hydrophilicity, and heterojunction-enhanced electron transfer promotes water oxidation activity.

Magnetic Field-Enhanced Acidic CO2 Electroreduction Reaction on Single Nickel-Site Catalysts

The synergistic integration of electrochemical reactions with an external magnetic field offers a powerful strategy for enhancing reaction performance. Herein, we introduce a flexible and continuously adjustable external magnetic field to enhance acidic CO2 reduction reaction (CO2RR) performance. In an acidic electrolyte (pH = 0.91), the initial Faradaic efficiency (FE) of the CO2RR for CO is only 18%, which can be increased to 63.2% when a 2 T magnetic field is applied. More importantly, the introduction of this external magnetic field enables the continuous switching of CO2 reduction products in a noncontact magnetic switching mode. Theoretical calculations demonstrate that the application of a magnetic field promotes CO2 adsorption at Ni sites and inhibits the hydrogen evolution reaction (HER), ultimately enhancing CO2RR activity and selectivity. This work provides fresh insight into how an external magnetic field promotes CO2RR performance.

Ce Salt-Assisted Construction of Bilayer Cu-Ce-O Nanostructure Arrays on Cu Foil Enhances Methanol Oxidation Performance

The construction of highly ordered nanostructures on copper offers significant advantages in energy conversion electrocatalysis, particularly as a potential alternative to platinum-based precious metal catalysts in the methanol oxidation process to prevent catalytic poisoning. However, the self-assembly and ordered growth of nanostructures on copper has been a research challenge. Herein, we report a Ce salt-assisted electrooxidation strategy for the first time to prepare bilayer Cu-Ce-O nanostructures on copper, containing Cu2O-Ce2O3 nanorods on the top and Cu2O nanoparticles next to the substrate. The incorporation of Ce salts into the electrolyte enables the controllable oriented growth of nanostructures from cubic nanoparticles to nanorods. Moreover, the high activity surface area of nanorods demonstrates enhanced catalytic activity and long-term stability (6 h) in methanol oxidation, exhibiting a current density of 71.5 mA cm-2 and 72 mV lower onset overpotential compared to blank Cu foil. Density functional theory calculations also demonstrate that Cu2O enhances the adsorption of CH3OH. This strategy provides new insights into the rational construction of sophisticated copper-based nanostructures, showing promising potential for applications in methanol catalysis.

Manipulation of Hydrogen Transfer Behaviors by RhCu Alloying Enables an All-in-one Sustainable "Furfural-Nitrate" System

Nitrate and furfural are typical wastes mainly from industrialization and agriculturalization progresses, and their clean conversions are still very challenging for a sustainable future. Nevertheless, scant attention has been devoted to the core issues: the rational integration of two wastes recycling and the targeted manipulation of hydrogen (H*) transfer behaviors to address their sluggish reaction kinetics. Herein, we report an all-in-one electrochemical energy system that is thermodynamically designed by coupling nitrate reduction (NO3RR) and furfural oxidation reactions (FORs) together. Particularly, the poor kinetics for both electrode reactions are efficaciously optimized by the bifunctional electrocatalyst of RhCu alloy nanowires on copper foam (RhCu NW/CF) with highly improved dual-directional H*-modulation performances, thus initializing NO3RR for NH3 synthesis at +0.31 V and driving FOR for H2 harvest at an onset potential lower than 0 V. Eventually, such integrated "Furfural-Nitrate" system can simultaneously effectuate the electricity energy supply (10.76 mW cm-2), wastewater purification, cathodic hydrogen storage (NH3), anodic H2 production, and biomass upgrading. Hence, it provides a promising perspective of "turning waste into treasure" in a rational manner, justifying its all-in-one property in addressing the global challenge of sustainable energy.

2D Carbon-Anchored Platinum-Based Nanodot Arrays as Efficient Catalysts for Methanol Oxidation Reaction

Ultrafine Pt-based alloy nanoparticles supported on carbon substrates have attracted significant attention due to their catalytic potential. Nevertheless, ensuring the stability of these nanoparticles remains a critical challenge, impeding their broad application. In this work, novel nanodot arrays (NAs) are introduced where superfine alloy nanoparticles are uniformly implanted in a 2D carbon substrate and securely anchored. Electrochemical testing of the PtCo NAs demonstrates exceptional methanol oxidation reaction (MOR) activity, achieving 1.25 A mg-1. Moreover, the PtCo NAs exhibit outstanding stability throughout the testing period, underscoring the effectiveness of the anchoring mechanism. Comprehensive characterization and theoretical calculations reveal that the 2D carbon-anchored structure optimizes the electronic structure and coordination environment of Pt, restricts nanoparticle migration, and suppresses transition metal dissolution. This strategy represents a major advancement in addressing the stability limitations of ultrafine nanoparticles in catalytic applications and offers broader insights into the design of next-generation catalysts with enhanced durability and performance.

Manipulating the Interfacial Hydrophobic Microenvironment via Electrolyte Engineering Promotes Electrocatalytic Fatty Alcohol Oxidation Coupled with Hydrogen Production

The selective oxidation of fatty alcohols to fatty acids represents a pivotal transformation in organic synthesis. Traditional methods often require harsh conditions and environmentally harmful oxidants or solvents. Electrocatalytic oxidation emerges as a promising green alternative, enabling mild oxidation in aqueous media and concurrent energy-efficient hydrogen production at the cathode. However, the poor solubility of fatty alcohols in water poses a significant challenge, reducing the reactant availability at the electrode surface, thereby hindering mass transfer and overall reaction rates. Herein, we develop an electrolyte engineering strategy that incorporates cetyltrimethylammonium hydroxide (CTAOH) as an additive. This strategy significantly enhances the oxidation current density of fatty alcohols as well as the production rate of fatty acids on a gold electrocatalyst. Through a mechanistic investigation combining experimental evidence from a quartz crystal microbalance (QCM) and in situ attenuated total reflectance surface-enhanced infrared spectroscopy (ATR-SEIRAS) with molecular dynamics (MD) simulations, we confirm that the preferential adsorption of CTAOH creates a hydrophobic interfacial microenvironment at the anode, promoting the enrichment of reactant at the electrode-electrolyte interface. This work highlights the significance of interfacial hydrophobicity modulation in boosting aqueous-phase electrocatalytic oxidation, paving the way for more efficient electrocatalytic transformations involving water-insoluble reactants.

Recyclable Hydrazine-Passivated NiBx/Ni Heterostructured Catalyst for Enhanced Hydrogenation of Polystyrene Pyrolysis Oil

Nickel boride (Ni2B) is known to be an excellent catalyst for hydrogenation of olefin structures under mild reaction conditions. Its susceptibility to oxidation in air environments, however, limits its practical applications. Here, a hydrazine-passivated nickel boride/nickel (NiBx/Ni) heterostructured catalyst is developed to address the oxidation problem while improving the conversion efficiency of styrene to ethylbenzene in a real polystyrene (PS) pyrolysis oil. The calculated turnover frequency for styrene to ethylbenzene conversion is 24.9 mmol/h·g, with 99.9% selectivity, representing a 38.3% improvement compared with the control Ni2B catalyst (18.0 mmol/h·g). This outstanding performance is attributed to the increased charge density on both Ni and B, induced by a strong hydrazine reductant, which surpasses other amine-structured ligands, such as ethanolamine and ethylamine. Additionally, the enhanced magnetic properties of NiBx/Ni, resulting from the Ni(111) nanocrystalline structure along the easy axis of magnetization, enable facile recovery after a neodymium magnet. The catalyst demonstrated excellent stability, retaining catalytic efficacy over five consecutive cycles with only a 4% loss in activity. This study highlights the potential of the NiBx/Ni catalyst for low-cost and efficient hydrogenation in industrial applications.

Stable Ni(II) sites in Prussian blue analogue for selective, ampere-level ethylene glycol electrooxidation

The industrial implementation of coupled electrochemical hydrogen production systems necessitates high power density and high product selectivity for economic viability and safety. However, for organic nucleophiles (e.g., methanol, urea, and amine) electrooxidation in the anode, most catalytic materials undergo unavoidable reconstruction to generate high-valent metal sites under harsh operation conditions, resulting in competition with oxygen evolution reaction. Here, we present unique Ni(II) sites in Prussian blue analogue (NiFe-sc-PBA) that serve as stable, efficient and selective active sites for ethylene glycol (EG) electrooxidation to formic acid, particularly at ampere-level current densities. Our in situ/operando characterizations demonstrate the robustness of Ni(II) sites during EG electrooxidation. Molecular dynamics simulations further illustrate that EG molecule tends to accumulate on the NiFe-sc-PBA surface, preventing hydroxyl-induced reconstruction in alkaline solutions. The stable Ni(II) sites in NiFe-sc-PBA anodes exhibit efficient and selective EG electrooxidation performance in a coupled electrochemical hydrogen production flow cell, producing high-value formic acid compared to traditional alkaline water splitting. The coupled system can continuously operate at stepwise ampere-level current densities (switchable 1.0 or 1.5 A cm-2) for over 500 hours without performance degradation.

A Dynamic Active Site for OER Catalysis at Nickel-Vanadium-Phosphide Depends on V Surface Position and Fe in Alkaline

Enhancing the rate of the oxygen evolution reaction (OER) by doping Ni-based electrocatalysts with guest metals other than Fe (V in this work) and the stability of the metal site should be assessed independent of Fe traces and in relation to the guest metal activity in solution. We examined OER catalysis and its sustainability at vanadium-doped nickel phosphide (NixPy-V) independent of the role of Fe traces in alkaline. V was included in NixPy by codeposition at cathodic bias (termed Vbulk) or postdeposition during the phosphide-to-hydroxide surface transformation at anodic bias in alkaline spiked with VCl3 (termed Vsurface). Doping with Vsurface strongly promoted OER and reduced the Tafel slope in KOH purified of Fe traces (Fe-free KOH), indicating a Vsurface-path lowering of overpotentials independent of and different from the mechanism via Fe surface sites at NiOxHy. A similar effect was not observed with Vbulk inclusion. Sustaining catalysis via Vsurface-sites required maintaining a sufficiently high activity of V in solution. The prominent role of Vsurface sites and the dependence of stability on solution condition are reminiscent of the behavior of Fe surface sites in NiOxHy. This work points to a trend of behavior of active site dynamics at Ni-based OER catalysts in alkaline and presents a question and insight on how to stabilize the guest-metal site at the solid-liquid interface.

CeO2 Modification Promotes the Oxidation Kinetics for Adipic Acid Electrosynthesis from KA Oil Oxidation at 200 mA cm-2

Electrocatalytic oxidation of cyclohexanol/cyclohexanone in water provides a promising strategy for obtaining adipic acid (AA), which is an essential feedstock in the polymer industry. However, this process is impeded by slow kinetics and limited Faradaic efficiency (FE) due to a poor understanding of the reaction mechanism. Herein, NiCo2O4/CeO2 is developed to enable the electrooxidation of cyclohexanol to AA with a 0.0992 mmol  h-1 cm-2 yield rate and 87 % Faradaic efficiency at a lower potential. Mechanistic investigations demonstrate that cyclohexanol electrooxidation to AA is a gradual oxidation process involving the dehydrogenation of cyclohexanol to cyclohexanone, the generation of 2-hydroxy cyclohexanone, and subsequent C-C cleavage. Theoretical calculations reveal that electronic interactions between CeO2 and NiCo2O4 decrease the energy barrier of cyclohexanone oxidation to 2-hydroxy cyclohexanone and inhibit the *OH to *O step, leading to AA electrosynthesis with a high yield rate and FE. Kinetic analysis further elucidates the effect of CeO2 on promoting cyclohexanone adsorption and activation on the electrode surface, thus facilitating the reaction kinetics. Moreover, a two-electrode flow reactor is constructed to produce 72.1 mmol AA and 10.4 L H2 by using KA oil as the anode feedstock at 2.5 A (200 mA cm-2), demonstrating promising potential.

Revealing the promoting effect of heterojunction on NiSx/MoO2 in urea oxidation assisted water electrolysis

Investigating efficient non-precious metal-based catalysts for water electrolysis to produce hydrogen is a significant and urgent need in the field of clean energy technologies. Moreover, utilizing transition metal dichalcogenides (TMDs) to replace the oxygen evolution reaction (OER) with the urea oxidation reaction (UOR), coupled with the hydrogen evolution reaction (HER), is an effective energy-saving hydrogen production method. A heterostructure NiSx/MoO2 catalyst was prepared by a simple method, which exhibits excellent activity for UOR, requiring only 1.4 V to reach 100 mA cm-2. The high performance is attributed to the presence of the heterostructure, which effectively promotes charge redistribution and optimizes the electronic structure of the catalyst, thereby enhancing its adsorption capacity for intermediates. As a result, an electrolyzer assembled with NiSx/MoO2 as a bifunctional catalyst demonstrates excellent catalytic activity, ensures stability for over 200 h at a current density of 10 mA cm-2, and achieves a hydrogen production rate of 0.402 mmol h-1 at a potential of 1.8 V.

High-Entropy Layered Double Hydroxides for Efficient Methanol Electrooxidation

The electrocatalytic methanol oxidation reaction (MOR) is considered as an effective method to replace oxygen evolution reaction (OER) for efficient hydrogen production. However, the sluggish kinetics and the difficulty of breaking C─H bond of the Ni-based catalysts limit further application. Herein, three high-entropy layered double hydroxides (HELHs), namely ZnNiFeCoV-HELH, ZnNiFeCoCr-HELH, and ZnNiFeCoAl-HELH (denoted as V-HELH, Cr-HELH, and Al-HELH, respectively), are successfully synthesized. Among them, the V-HELH displays the lowest potential of 1.39 V at 100 mA cm-2 compared to Cr-HELH (1.41 V) and Al-HELH (1.44 V). After five cycles, the formate yield of V-HELH maintains over 95% of the first cycle with excellent stability. Such outstanding performance surpasses that of most state-of-the-art MOR catalysts reported so far. A series of experiments reveal that the V-HELH exhibits the fastest reaction kinetics and the largest number of active Ni3+ species. Further investigations and theoretical calculations prove that the V-HELH shows the strongest methanol adsorption with the lowest energy of -3.31 eV. The introduction of vanadium (V) with relatively larger tensile strain optimizes the d─band center of V-HELH (-0.54 eV) and lowers the energy barrier (-1.62 eV) from *CH3O to *CH2O. This work provides new insights for rational design of efficient MOR electrocatalysts.

Enhancing the Kinetics of Glucose Electro-Oxidation by Modulating the Binding Energy of Hydroxyl on Cobalt-Based Catalysts

Replacing the sluggish anodic water oxidation reaction with the glucose oxidation reaction (GOR) offers an energy-saving strategy to obtain value-added products during the hydrogen production process. However, rational design of the GOR electrocatalyst with an explicit structure-property relationship remains a challenge. In this study, by using cobalt chalcogenides as model catalysts, we performed an in-depth study of the GOR catalytic mechanism of CoS and CoSe nanosheets. Experimental and theoretical results revealed that the reaction pathway on cobalt chalcogenides strongly depends on their binding energy to hydroxyl (OHBE). For CoS with a weak OHBE, the reaction proceeds through an "electrophilic oxygen" route. While for CoSe, due to the strong OHBE, a surface reconstruction occurs before the GOR and therefore follows the "electrochemical-chemical" route. Inspired by these findings, a customized strategy was proposed to regulate the OHBE of the catalysts, which involved introducing F atoms into CoS to enhance its OHBE, and weakening the OHBE of CoSe by doping with Zn atoms. The optimized F-doped CoS and Zn-doped CoSe catalysts both exhibited significantly improved performance for GOR. This study thus provides a verifiable paradigm for improving the GOR performance via a customized strategy and sheds light on the design of novel catalysts in the future.

Anti-poisoning of CO and carbonyl species over Pd catalysts during the electrooxidation of ethylene glycol to glycolic acid at elevated current density

The electrocatalytic oxidation of ethylene glycol (EG) to produce valuable glycolic acid (GLYA) is a promising strategy to tackle EG overcapacity. Despite the good selectivity of Pd for EG oxidation, its performance is constrained by limited mass activity and toxicity of intermediates like CO or CO-analogues. This study reports the alloying of Pd with Ni and Mo metals to enhance the activity and durability of EG oxidation in alkaline media. Notably, the peak current density reached up to 2423 mA mg-1, double that of pristine Pd/C, accompanied by a GLYA Faraday efficiency up to 87.7%. Moreover, PdNiMo/C exhibited a 5-fold slower activity decline compared to Pd/C. In situ experiments and theoretical analysis reveal that Ni and Mo synergistically strengthen the oxygen affinity of the catalyst, facilitating the generation of *OH radicals at lower potentials, thereby accelerating EG oxidation kinetics. Additionally, Ni incorporation prevents C-C bond cleavage and weakens CO adsorption, effectively mitigating catalyst poisoning.

Methanol-Enhanced Low-Cell-Voltage Hydrogen Generation at Industrial-Grade Current Density by Triadic Active Sites of Pt1-Pdn-(Ni,Co)(OH)x

Methanol (ME) is a liquid hydrogen carrier, ideal for on-site-on-demand H2 generation, avoiding its costly and risky distribution issues, but this "ME-to-H2" electric conversion suffers from high voltage (energy consumption) and competitive oxygen evolution reaction. Herein, we demonstrate that a synergistic cofunctional Pt1Pdn/(Ni,Co)(OH)x catalyst with Pt single atoms (Pt1) and Pd nanoclusters (Pdn) anchored on OH-vacancy(VOH)-rich (Ni,Co)(OH)x nanoparticles create synergistic triadic active sites, allowing for methanol-enhanced low-voltage H2 generation. For MOR, OH* is preferentially adsorbed on Pdn and then interacts with the intermediates (such as *CHO or *CHOOH) adsorbed favorably on neighboring Pt1 with the assistance of hydrogen bonding from the surface hydrogen of (Ni,Co)(OH)x. The enhanced selectivity of the *CHOOH pathway, instead of *CO, sustains the MOR activity to a practically high current density. For HER, triadic Pt1, Pdn, and OH-vacancy sites on (Ni,Co)(OH)x create an "acid-base" microenvironment to facilitate water adsorption and splitting, forming H* species on Pt1 and Pdn, and *OH at the vacancy, to promote efficient H2 evolution from the asymmetric Pt1 and Pdn sites via the Tafel mechanism. The triadic-site synergy opens new avenues for the design and synthesis of highly efficient and stable cofunctional catalysts for "on-site-on-demand" H2 production, here facilitated by liquid methanol.

Cation-Vacancy Engineering in Cobalt Selenide Boosts Electrocatalytic Upcycling of Polyester Thermoplastics at Industrial-Level Current Density

The past decades have witnessed the increasing accumulation of plastics, posing a daunting environmental crisis. Among various solutions, converting plastics into value-added products presents a significant endeavor. Here, an electrocatalytic upcycling route that efficiently converts waste poly(butylene terephthalate) plastics into high-value succinic acid with high Faradaic efficiency of 94.0% over cation vacancies-rich cobalt selenide catalyst is reported, showcasing unprecedented activity (1.477 V vs. RHE) to achieve an industrial-level current density of 1.5 A cm-2, and featuring a robust operating durability (≈170 h). In particular, when combining butane-1,4-diol monomer oxidation (BOR) with hydrogen evolution using the cation vacancy-engineered cobalt selenide as bifunctional catalyst, a relatively low cell voltage of 1.681 V is required to reach 400 mA cm-2, manifesting an energy-saving efficiency of ≈15% compared to pure water splitting. The mechanism and reaction pathways of BOR over the vacancies-rich catalyst are first revealed through theoretical calculations and in-situ spectroscopic investigations. The generality of this catalyst is evidenced by its powerful electrocatalytic activity to other polyester thermoplastics such as poly(butylene succinate) and poly(ethylene terephthalate). These electrocatalytic upcycling strategies can be coupled with the reduction of small molecules (e.g., H2O, CO2, and NO3 -), shedding light on energy-saving production of value-added chemicals.

Fine-tuning d-p hybridization in Ni-Bx cocatalyst for enhanced photocatalytic H2 production

The H2-evolution kinetics play a pivotal role in governing the photocatalytic hydrogen-evolution process. However, achieving precise regulation of the H-adsorption and H-desorption equilibrium (Hads/Hdes) still remains a great challenge. Herein, we propose a fine-tuning d-p hybridization strategy to precisely optimize the Hads/Hdes kinetics in a Ni-Bx modified CdS photocatalyst (Ni-Bx/CdS). X-ray absorption fine-structure spectroscopy and theoretical calculations reveal that increasing B-atom amount in the Ni-Bx cocatalyst gradually strengthens the d-p orbital interaction between Ni3d and B2p, resulting in a consecutive d-band broadening and controllable d-band center on Ni active sites. The above consecutive d-band optimization allows for precise modulation of the Hads/Hdes dynamics in the Ni-Bx/CdS, ultimately demonstrating a remarkable H2-evolution activity of 13.4 mmol g-1 h-1 (AQE = 56.1 %). The femtosecond transient absorption spectroscopy further confirms the rapid electron-transfer dynamics in the Ni-Bx/CdS photocatalyst. This work provides insights into the optimal design of prospective H2-evolution catalysts.

Efficiently Re-Utilizing the High-Value Metals in the Spent LiNi1-x-yMnxCoyO2 for the Trifunctional Electrocatalysts by a Novel One-Pot Method

Traditional hydrometallurgy methods for recycling the spent lithium-ion battery materials face some challenges, including the complex processes, and difficulties in separating Ni/Co/Mn. To address these issues, this work proposes a simple one-pot method to achieve a high Li leaching efficiency (99.2%) and simultaneously transform the majority of Ni (99.5%) and Co (99.9%) into a high-performance multifunctional electrocatalyst (LNMCO-HS-180). LNMCO-HS-180 with single-phase structure shows a hollow microsphere morphology. LNMCO-HS-180 can efficiently catalyze the oxygen reduction (ORR), oxygen evolution (OER), and methanol oxidation reactions (MOR), with the ORR half-wave potential of 0.732 V and, OER potential of 1.469 V at 10 mA cm-2. This is mainly attributed to the unique hollow microsphere morphology, suitable Ni/Co/Mn oxidation states, and reduction in the free energy barriers for OER and ORR. Additionally, LNMCO-HS-180 exhibits an MOR potential of only 1.43 V at 100 mA cm-2 and excellent formate selectivity (>99%).

A Cosolvent Electrolyte Boosting Electrochemical Alkynol Semihydrogenation

Green electricity-driven alkenol electrosynthesis via electrocatalytic alkynol semihydrogenation represents a sustainable route to conventional thermocatalysis. Both the electrocatalyst and electrolyte strongly impact the semihydrogenation performance. Despite significant progress in developing sophisticated electrocatalysts, a well-designed electrolyte in conjunction with industrial catalysts is an attractive strategy to advance the industrialization process of electrocatalytic alkynol semihydrogenation, but remains unexplored. Here, we develop a dimethyl sulfoxide (DMSO)-H2O cosolvent electrolyte for electrocatalytic alkynol semihydrogenation. At an alkynol conversion of about 100%, the DMSO-H2O electrolyte compared to the DMSO-free counterpart enables the alkenol selectivity on Cu catalysts to be promoted from 60-70% to over 90% at all measured current densities; meanwhile, the reaction rate is slightly decreased due to the inhibited water dissociation. Mechanistic studies reveal that the strong hydrogen-bond interactions between DMSO and H2O suppress the dissociation of interfacial H2O, leading to a decreased H* coverage at the electrode surface. The decreased H* coverage hinders the overhydrogenation of alkynols and favors the production of alkenols. Remarkably, the DMSO-induced enhancement of alkenol selectivity is applicable to a set of commercial catalysts and to the semihydrogenation of various alkynols. Eventually, a scaled-up 3 × 100 cm2 electrolyzer stack is established to achieve an alkynol conversion of ∼96% and an alkenol selectivity of ∼95% in the cosolvent electrolyte. This work not only presents an electrolyte strategy for boosting alkenol electrosynthesis, but also highlights the possibility of sustainable alkenol electro-production.

A Green and Efficient Electrocatalytic Route for the Highly-Selective Oxidation of C-H Bonds in Aromatics over 1D Co3O4-Based Nanoarrays

Electrocatalytic oxidation of C-H bonds in hydrocarbons represents an efficient and sustainable strategy for the synthesis of value-added chemicals. Herein, a highly selective and continuous-flow electrochemical oxidation process of toluene to various oxygenated products (benzyl alcohol, benzaldehyde, and benzyl acetate) is developed with the electrocatalytic membrane electrodes (ECMEs). The selectivity of target products can be manipulated via surface and interface engineering of Co3O4-based electrocatalysts. We achieved a high benzaldehyde selectivity of 90 % at a toluene conversion of 47.6 % using 1D Co3O4 nanoneedles (NNs) loaded on a microfiltration (MF) titanium (Ti) membrane, i.e, Co3O4 NNs/Ti. In contrast, the main product shifted to benzyl alcohol with a selectivity of 90.1 % at a conversion of 32.1 % after modifying MnO2 nanosheets (NSs) on Co3O4 NNs/Ti (Co3O4@MnO2/Ti) catalyst. Moreover, benzyl acetate product can be obtained with a selectivity of 92 % at a conversion of 58.5 % at high current density (>1.5 mA cm-2), demonstrating that the pathway of toluene oxidation is readily maneuvered. DFT results reveal that modifying MnO2 on Co3O4 optimizes the electron structure of Co3O4@MnO2/Ti and modulates the adsorption behavior of intermediate species. This work demonstrates a sustainable, efficient, and continuous-flow process for precise control over the production selectivity of value-added oxygenated derivatives in the electrochemical oxidation of aromatic hydrocarbons.

Ozone-Assisted Cu-Based Catalysts for the Efficient Electro-Reforming Glycerol to Formic Acid

Glycerol electrooxidation reaction (GOR) to produce value-added chemicals, such as formic acid, could make more efficient use of abundant glycerol and meet future demand for formic acid as a fuel for direct or indirect formic acid fuel cells. Non-noble metal Cu-based catalysts have great potential in electro-reforming glycerol to formic acid. However, the high activity, selectivity and stability of Cu based catalysts in GOR cannot be achieved simultaneously. Here, we used ozone-assisted electrocatalyst to convert glycerol to formic acid under alkaline conditions, the onset potential was reduced by 60 mV, the Faraday efficiency (FE) reached 95 %. The catalyst has excellent stability within 300 h at the current density of 10 mA cm-2. The electron spin resonance proved that ozone produced superoxide anion during the GOR. In situ Raman spectroscopy, electrochemical studies showed that glycerol can be activated with ozone in GOR, and the C-C bond can be broken to reduce the polymerization of glycerol on the catalyst surface, so as to produce more formic acid at a lower voltage. Moreover, the removal of dissolved O3 from water can be up to 100 % after 30 minutes of GOR reaction at a solubility of 50 mg L-1 as measured by UV-VIS spectrophotometry.

Optimizing surface active sites via burying single atom into subsurface lattice for boosted methanol electrooxidation

The precise fabrication and regulation of the stable catalysts with desired performance still challengeable for single atom catalysts. Here, the Ru single atoms with different coordination environment in Ni3FeN lattice are synthesized and studied as a typical case over alkaline methanol electrooxidation. The Ni3FeN with buried Ru atoms in subsurface lattice (Ni3FeN-Ruburied) exhibits high selectivity and Faradaic efficiency of methanol to formate conversion. Meanwhile, operando spectroscopies reveal that the Ni3FeN-Ruburied exhibits an optimized adsorption of reactants along with an inhibited surface structural reconstruction. Additional theoretical simulations demonstrate that the Ni3FeN-Ruburied displays a regulated local electronic states of surface metal atoms with an optimized adsorption of reactants and reduced energy barrier of potential determining step. This work not only reports a high-efficient catalyst for methanol to formate conversion in alkaline condition, but also offers the insight into the rational design of single atom catalysts with more accessible surficial active sites.

Fundamentals and Challenges of Ligand Modification in Heterogeneous Electrocatalysis

The development of efficient catalytic materials in the energy field could promote the structural transformation from traditional fossil fuels to sustainable energy. In heterogeneous catalytic reactions, ligand modification is an effective way to regulate both electronic and steric structures of catalytic sites, thus paving a prospective avenue to design the interfacial structures of heterogeneous catalysts for energy conversion. Although great achievements have been obtained for the study and applications of heterogeneous ligand-modified catalysts, the systematical refinements of ligand modification strategies are still lacking. Here, we reviewed the ligand modification strategy from both the mechanistic and applicable scenarios by focusing on heterogeneous electrocatalysis. We elucidated the ligand-modified catalysts in detail from the perspectives of basic concepts, preparation, regulation of physicochemical properties of catalytic sites, and applications in different electrocatalysis. Notably, we bridged the electrocatalytic performance with the electronic/steric effects induced by ligand modification to gain intrinsic structure-performance relations. We also discussed the challenges and future perspectives of ligand modification strategies in heterogeneous catalysis.

Polyelectrolyte Additive-Modulated Interfacial Microenvironment Boosting CO2 Electrolysis in Acid

Acidic CO2 electrolysis offers a promising strategy to achieve high carbon utilization and high energy efficiency. However, challenges still remain in suppressing the competitive hydrogen evolution reaction (HER) and improving product selectivity. Although high concentrations of potassium ions (K+) can suppress HER and accelerate CO2 reduction, they still inevitably suffer from salt precipitation problems. In this study, we demonstrate that the sulfonate-based polyelectrolyte, polystyrene sulfonate (PSS), enables to reconstruct the electrode-electrolyte interface to significantly enhance the acidic CO2 electrolysis. Mechanistic studies reveal that PSS induces high local K+ concentrations through the electrostatic interaction between PSS anions and K+. In situ spectroscopy reveals that PSS reshapes the interfacial hydrogen-bond (H-bond) network, which is attributed to the H-bonds between PSS anions and hydrated proton, as well as the steric hindrance of the additive molecules. This greatly weakens proton transfer kinetics and leads to the suppression of undesirable HER. As a result, a Faradaic efficiency of 93.9 % for CO can be achieved at 250 mA cm-2, simultaneous with a high single-pass carbon efficiency of 72.2 % on commercial Ag catalysts in acid. This study highlights the important role of the electrode-electrolyte interface induced by polyelectrolyte additives in promoting electrocatalytic reactions.

Dynamic Self-Healing of the Reconstructed Phase in Perovskite Oxides for Efficient and Stable Electrocatalytic OER

Neither electrocatalytic activity nor structural stability is inconsequential in water electrolysis. Unfortunately, they have to be compromised in practice, especially in the anodic redox chemistry of lattice oxygen. Herein, the discovery of a La1- xCexFeO3 perovskite is presented which shows both good stability and high catalytic activity. Using advanced operando characterizations, it is identified that the self-healing evolution of the La1- xCexFeO3 perovskite plays a key role during water oxidation in the lattice oxygen-mediated mechanism (LOM) pathway. Unlike irreversible reconstruction, the formation of reconstructed active-phase α-FeOOH is reversed by re-crystallization of surface La1- xCexFeO3 upon return to noncatalytic conditions. The self-healing transformation of the α-FeOOH termination layer on the stable La1- xCexFeO3 core imparts remarkable long-term stability as well as excellent electrocatalytic performance. As a result, a composition La0.9Ce0.1FeO3@FeOOH is designed that exhibits ultralow overpotentials of 257 and 312 mV to achieve 10 and 100 mA cm-2, respectively. The findings provide insight into self-healing behavior toward engineering perovskite oxides for efficient and stable oxygen electrocatalysis.

Self-Reconstructed Amorphous CoOx/NiCoB Heterostructure Catalysts for Enhanced HER Performance

Amorphous electrocatalysts exhibit potentials as precursors for triggering the in situ reconstruction to generate the real catalytic active species toward electrochemical processes. In this work, a new kind of amorphous Ni-Co-B alloy pre-catalysts for hydrogen evolution reaction (HER) is reported, which is obtained via a facile electroless plating strategy on the nickel foam (NF). Interestingly, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and morphological characterizations identify the in situ reconstruction process during HER accompanied by the preferential leaching of surface B species and the formation of amorphous CoOx nanosheet arrays as the real active sites. Benefiting from the synergistic effect between the surface CoOx layer and the inner unaltered NiCoB phase, the resultant CoOx/NiCoB heterostructure catalyst achieves a low overpotential of 209 mV at the elevated current density of 500 mA cm-2 and maintains stability for 300 h without significant attenuation. Theoretical calculation reveals the electron reconfiguration at the interfaces between the newly formed CoOx and inner NiCoB phases, which is favorable for the stabilization of reconstructed active oxide layers at the reductive potentials for catalyzing HER. Moreover, the CoOx/NiCoB heterostructure optimizes hydrogen adsorption free energies, thereby enhancing HER catalytic activity.

Construction of iron-doped nickel cobalt phosphide nanoparticles via solvothermal phosphidization and their application in alkaline oxygen evolution

Multi-metallic phosphides offer the possibility to combine the strategies of surface reconstruction, electronic interaction and mechanistic pathway tuning to achieve high electrocatalytic oxygen evolution activity. Here, iron-doped nickel cobalt phosphide nanoparticles (FexCoyNi2-x-yP) with the crystalline NiCoP phase are for the first time synthesized by the solvothermal phosphidization method via the reaction between metal-organic frameworks and white phosphorus. When used to electrochemically catalyze oxygen evolution reaction (OER), the Fe0.4Co0.8Ni0.8P supported by nickel foam requires only 248 mV overpotential to achieve 10 mA cm-2 current densities, and is robust towards the long-term OER in 1 M KOH. The higher number of electrochemically active sites can account for the good OER activity, along with the improved intrinsic activity which is caused by the electron interaction that optimizes the adsorption energy of hydroxyl intermediates, and that increases the acidity of high-valent metal centers. The OER mechanistic pathway involves both adsorbate and lattice oxygen. Surface conversion is observed after OER in alkaline solution, and metal phosphide layer transforms to metal oxides and (oxy)hydroxides.

p-n-Type LaCoO3/NiFe LDH Heterostructures for Enhanced Photogenerated Carrier-Assisted Electrocatalytic Oxygen Evolution Reaction

The oxygen evolution reaction (OER) poses a significant kinetic challenge for various critical energy conversion and storage technologies including electrocatalytic water splitting and metal-air batteries. In this study, a LaCoO3/NiFe layered double hydroxide (LDH) catalyst was synthesized through the in situ growth of n-type NiFe LDH on the surface of the p-type LaCoO3 semiconductor, resulting in a p-n heterostructure for a photogenerated carrier-assisted electrocatalytic OER (PCA-eOER). The alignment of their band structures facilitates the formation of an internal electric field at the heterojunction interface, which promotes the creation of oxygen vacancies and enhances electron transport. Under illumination, the expanded visible-light absorption range and built-in electric field work synergistically to improve the generation and separation of photogenerated carriers. Meanwhile, the accumulation of photogenerated holes on the surface of NiFe LDH results in an enhancement in the concentration of high-valent active metal sites, resulting in a boost in the PCA-eOER efficiency. The LaCoO3/NiFe LDH has achieved an overpotential of 260 mV at the current density of 10 mA cm-2, 50 mV lower than in the absence of illumination. In addition, LaCoO3/NiFe LDH was assembled into an alkaline water electrolyzer and zinc-air batteries (ZABs), showing excellent practical application capability. We explored the application of LaCoO3 in a PCA-eOER, which provides a concept for designing PCA-eOER catalysts and advancing the development of perovskite-based catalysts for clean energy conversion technology.

Modification d x 2 - y 2 ${{d}_{{{x}^2} - {{y}^2}}}$ Orbital Electronic States in Nickel-Based Hydroxides Via Cobalt/Iron Co-Doping for High-Efficiency Methanol Electrooxidation

The nickel hydroxide-based (Ni(OH)2) methanol-to-formate electrooxidation reaction (MOR) performance is greatly related to thed x 2 - y 2 ${{d}_{{{x}^2} - {{y}^2}}}$ orbital electronic states. Hence, optimizing thed x 2 - y 2 ${{d}_{{{x}^2} - {{y}^2}}}$ orbital electronic states to achieve enhanced MOR activities are highly desired. Here, cobalt (Co) and iron (Fe) doping are used to modify thed x 2 - y 2 ${{d}_{{{x}^2} - {{y}^2}}}$ orbital electronic states. Although both dopants can broaden thed x 2 - y 2 ${{d}_{{{x}^2} - {{y}^2}}}$ orbital; however, Co doping leads to an elevation in the energy level ofd x 2 - y 2 ${{d}_{{{x}^2} - {{y}^2}}}$ highest occupied crystal orbital (HOCO), whereas Fe doping results in its reduction. Such a discrepancy in the regulation ofd x 2 - y 2 ${{d}_{{{x}^2} - {{y}^2}}}$ orbital electronic states stems from the disparate partial electron transfer mechanisms amongst these transition metal ions, which possess distinct energy level and occupancy of d orbitals. Motivated by this finding, the NiCoFe hydroxide is prepared and exhibited an excellent MOR performance. The results showed that the Co dopants effectively suppress the partial electron transfer from Ni to Fe, combined with thed x 2 - y 2 ${{d}_{{{x}^2} - {{y}^2}}}$ orbital broadening induced by NiO6 octahedra distortion, endowing NiCoFe hydroxide with highd x 2 - y 2 ${{d}_{{{x}^2} - {{y}^2}}}$ HOCO and broadd x 2 - y 2 ${{d}_{{{x}^2} - {{y}^2}}}$ orbital. It is believed that the work gives an in-depth understanding ond x 2 - y 2 ${{d}_{{{x}^2} - {{y}^2}}}$ orbital electronic states regulation in Ni(OH)2, which is beneficial for designing Ni(OH)2-based catalysts with high MOR performance.

Parameterization and quantification of two key operando physio-chemical descriptors for water-assisted electro-catalytic organic oxidation

Electro-selective-oxidation using water as a green oxygen source demonstrates promising potential towards efficient and sustainable chemical upgrading. However, surface micro-kinetics regarding co-adsorption and reaction between organic and oxygen intermediates remain unclear. Here we systematically study the electro-oxidation of aldehydes, alcohols, and amines on Co/Ni-oxyhydroxides with multiple characterizations. Utilizing Fourier transformed alternating current voltammetry (FTacV) measurements, we show the identification and quantification of two key operando parameters (ΔIharmonics/IOER and ΔVharmonics) that can be fundamentally linked to the altered surface coverage ( Δ θ OH * / θ OH * OER ) and the changes in adsorption energy of vital oxygenated intermediates (Δ G OH * EOOR - Δ G OH * OER ), under the influence of organic adsorption/oxidation. Mechanistic analysis based on these descriptors reveals distinct optimal oxyhydroxide surface states for each organics, and elucidates the critical catalyst design principles: balancing organic and M3+δ-OH* coverages and fine-tuning ΔG for key elementary steps, e.g., via precise modulation of chemical compositions, crystallinity, defects, electronic structures, and/or surface bimolecular interactions.

Self-sacrificing and self-supporting biomass carbon anode-assisted water electrolysis for low-cost hydrogen production

Electrooxidation of renewable and CO2-neutral biomass for low-cost hydrogen production is a promising and green technology. Various biomass platform molecules (BPMs) oxidation assisted hydrogen production technologies have obtained noticeable progress. However, BPMs anodic oxidation is highly dependent on electrocatalysts, and the oxidation mechanism is ambiguous. Meanwhile, the complexity and insolubility of natural biomass severely constrain the efficient utilization of biomass resources. Here, we develop a self-sacrificing and self-supporting carbon anode (SSCA) using waste corncobs. The combined results from multiple characterizations reveal that the structure-property-activity relationship of SSCA in carbon oxidation reaction (COR). Theoretical calculations demonstrate that carbon atoms with a high spin density play a pivotal role in reducing the adsorption energy of the reactive oxygen intermediate (*OH) during the transition from OH- to *OH, thereby promoting COR. Additionally, the HER||COR system allows driving a current density of 400 [Formula: see text] at 1.24 V at 80 °C, with a hydrogen production electric consumption of 2.96 kWh Nm-3 (H2). The strategy provides a ground-breaking perspective on the large-scale utilization of biomass and low-energy water electrolysis for hydrogen production.

Molybdenum iron carbide-copper hybrid as efficient electrooxidation catalyst for oxygen evolution reaction and synthesis of cinnamaldehyde/benzalacetone

Oxygen evolution reaction (OER) is the efficiency limiting half-reaction in water electrolysis for green hydrogen production due to the 4-electron multistep process with sluggish kinetics. The electrooxidation of thermodynamically more favorable organics accompanied by CC coupling is a promising way to synthesize value-added chemicals instead of OER. Efficient catalyst is of paramount importance to fulfill such a goal. Herein, a molybdenum iron carbide-copper hybrid (Mo2C-FeCu) was designed as anodic catalyst, which demonstrated decent OER catalytic capability with low overpotential of 238 mV at response current density of 10 mA cm-2 and fine stability. More importantly, the Mo2C-FeCu enabled electrooxidation assisted aldol condensation of phenylcarbinol with α-H containing alcohol/ketone in weak alkali electrolyte to selective synthesize cinnamaldehyde/benzalacetone at reduced potential. The hydroxyl and superoxide intermediate radicals generated at high potential are deemed to be responsible for the electrooxidation of phenylcarbinol and aldol condensation reactions to afford cinnamaldehyde/benzalacetone. The current work showcases an electrochemical-chemical combined CC coupling reaction to prepare organic chemicals, we believe more widespread organics can be synthesized by tailored electrochemical reactions.

Modulating Silver Performance in Electrocatalytic Oxidation of HCHO via SMSI between Ag-Co3O4 Interfaces

The replacement of oxygen evolution reactions with organic molecule oxidation reactions to enable energy-efficient hydrogen production has been a subject of interest. However, further reducing reaction energy consumption and releasing hydrogen from organic molecules continue to pose significant challenges. Herein, a strategy is proposed to produce hydrogen and formic acid from formaldehyde using Ag/Co3O4 interface catalysts at the anode. The key to improving the performance of Ag-based catalysts for formaldehyde oxidation lies in the strong SMSI achieved through the well-designed "spontaneous redox reaction" between Ag and Co3O4 precursors. Nano-sized Ag particles are uniformly dispersed on Co3O4 nanosheets, and electron-deficient Agδ+ are formed by the SMSI between Ag and Co3O4. Ag/Co3O4 demonstrates exceptional formaldehyde oxidation activity at low potentials of 0.32 V versus RHE and 0.65 V versus RHE, achieving current densities of 10 and 100 mA cm-2, respectively. The electrolyzer "Ag/Co3O4||20% Pt/C" achieves over 195% hydrogen efficiency and over 98% formic acid selectivity, maintaining stable operation for 60 hours. This work not only presents a novel approach to precisely modulate Ag particle size and interface electronic structure via SMSI, but also provides a promising approach to efficient and energy-saving hydrogen production and the transformation of harmful formaldehyde.

Facilitating Formate Selectivity via Optimizing eg* Band Broadening in NiMn Hydroxides for Ethylene Glycol Electro-Oxidation

Ethylene glycol electro-oxidation reaction (EGOR) on nickel-based hydroxides (Ni(OH)2) represents a promising strategy for generating value-added chemicals, i.e. formate and glycolate, and coupling water-electrolytic hydrogen production. The high product selectivity was one of the most significant area of polyols electro-oxidation process. Yet, developing Ni(OH)2-based EGOR electrocatalyst with highly selective product remains a challenge due to the unclear cognition about the EGOR mechanism. Herein, Mn-doped Ni(OH)2 catalysts were utilized to investigate the EGOR mechanism. Experimental and calculation results reveal that the electronic states of eg* band play an important role in the catalytic performance and the product selectivity for EGOR. Broadening the eg* band could effectively enhance the adsorption capacity of glyoxal intermediates. On the other hand, this enhanced adsorption could lead to reduced side reactions associated with glycolate formation, simultaneously promoting the cleavage of C-C bonds. Consequently, the selectivity for formate was notably augmented by these enhancements. This work offers new insights into the regulation of catalyst electronic states for improving polyol electrocatalytic activity and product selectivity.

Modulation in work function of CoTe as bifunctional electrocatalyst for rechargeable zinc air battery

The sluggish kinetics and inferior stability of oxygen electrocatalyst in rechargeable zinc air battery (ZAB) hamper its industrialization. In this work, we activate cobalt telluride (CoTe) by introduction of metallic cobalt (Co) to modulate the work function to facilitate the electron transfer from Co to CoTe during oxygen catalysis; additionally, the three-dimensional porous carbon nanosheets (3DPC) are invited to reduce the resistance towards electrolyte/oxygen diffusion. Thereby, Co-CoTe@3DPC only demands 280 mV overpotential to reach 10 mA cm-2 under alkaline oxygen evolution reaction (OER) condition, relatively lower than commercial iridium oxides (IrO2); besides, the operando electrochemical impedance spectroscopy (EIS) indicates a better resistance towards surface reconstruction than Co@3DPC leading to a superior stability. A Pt-like oxygen reduction reaction (ORR) performance, half-wave potential associated with kinetic current density, is achieved for Co-CoTe@3DPC. A maximum power density of 203 mW cm-2 is achieved and sustains for 800 h. Furthermore, the all-solid-state ZAB offers 97 mW cm-2. Theoretical calculation suggests that the incorporation of metallic Co to CoTe maintains the superb ORR activity and promotes the OER catalysis.

Edge-Rich Pt-O-Ce Sites in CeO2 Supported Patchy Atomic-Layer Pt Enable a Non-CO Pathway for Efficient Methanol Oxidation

Rational design of efficient methanol oxidation reaction (MOR) catalyst that undergo non-CO pathway is essential to resolve the long-standing poisoning issue. However, it remains a huge challenge due to the rather difficulty in maximizing the non-CO pathway by the selective coupling between the key *CHO and *OH intermediates. Here, we report a high-performance electrocatalyst of patchy atomic-layer Pt epitaxial growth on CeO2 nanocube (Pt ALs/CeO2) with maximum electronic metal-support interaction for enhancing the coupling selectively. The small-size monolayer material achieves an optimal geometrical distance between edge Pt-O-Ce sites and *OH absorbed on CeO2, which well restrains the dehydrogenation of *CHO, resulting in the non-CO pathway. Meanwhile, the *CHO/*CO intermediate generated at inner Pt-O-Ce sites can migrate to edge, inducing the subsequent coupling reaction, thus avoiding poisoning while promoting reaction efficiency. Consequently, Pt ALs/CeO2 exhibits exceptionally catalytic stability with negligible degradation even under 1000 s pure CO poisoning operation and high mass activity (14.87 A/mgPt), enabling it one of the best-performing alkali-stable MOR catalysts.

A Stable High-Performance Zn-Ion Batteries Enabled by Highly Compatible Polar Co-Solvent

Uncontrollable growth of Zn dendrites, irreversible dissolution of cathode material and solidification of aqueous electrolyte at low temperatures severely restrict the development of aqueous Zn-ion batteries. In this work, 2,2,2-trifluoroethanol (TFEA) with a volume fraction of 50% as a highly compatible polar-solvent is introduced to 1.3 M Zn(CF3SO3)2 aqueous electrolyte, achieving stable high-performance Zn-ion batteries. Massive theoretical calculations and characterization analysis demonstrate that TFEA weakens the tip effect of Zn anode and restrains the growth of Zn dendrites due to electrostatic adsorption and coordinate with H2O to disrupt the hydrogen bonding network in water. Furthermore, TFEA increases the wettability of the cathode and alleviates the dissolution of V2O5, thus improving the capacity of the full battery. Based on those positive effects of TFEA on Zn anode, V2O5 cathode, and aqueous electrolyte, the Zn//Zn symmetric cell delivers a long cycle-life of 782 h at 5 mA cm-2 and 2 mA h cm-2. The full battery still declares an initial capacity of 116.78 mA h g-1, and persists 87.73% capacity in 2000 cycles at -25 °C. This work presents an effective strategy for fully compatible co-solvent to promote the stability of Zn anode, V2O5 cathode and aqueous electrolyte for high-performance Zn-ion batteries.

High-Dimensional Nb2O5 with NbO6 Octahedra for Efficient Electrocatalytic Upgrading of Methanol to Formate

Facilitating the selective electrochemical oxidation of methanol into value-added formate is essential for electrochemical refining. Here we propose a high-dimensional Nb2O5 on Ni foam (Nb2O5-HD@NF) composite as anode for methanol oxidation reaction (MOR) for efficient production of formate. In an electrolyte containing 3 M methanol aqueous solution, the Nb2O5-HD@NF anode requires only 240 mV overpotential to deliver an industrial-level current density of 100 mA cm-2 with a formate Faraday efficiency of 100%. In situ Raman and electrochemical kinetic analyses reveal that the origin of the excellent activity in 3 M methanol electrolyte can be ascribed to the NbO6 octahedra as active sites and the Lewis acid sites on the surface of Nb2O5-HD. This work may pave a way for the design of non-noble metal electrocatalysts with surface acidity engineering for the effective electrocatalytic upgrading of biomass molecules.

NiCo-Phosphide Bifunctional Electrocatalyst Realizes Electrolysis of Sugar Solution to Formic Acid and Hydrogen

As a promising liquid hydrogen carrier, formic acid is essential for hydrogen energy. Glucose, as the most widely distributed monosaccharide in nature, is valuable for co-electrolysis with water to produce formic acid and hydrogen, though achieving high formate yield and current density remains challenging. Herein, a nanostructured NiCoP on a 3D Ni foam catalyst enables efficient electrooxidation of glucose to formate, achieving an 85% yield and 200 mA current density at 1.47 V vs RHE. The catalyst forms a NiCoOOH/NiCoP/Ni foam sandwich structure via anodic oxidative reconstruction, with NiCoOOH as the active site and NiCoP facilitating electron conduction. Additionally, NiCoP/Ni foam serves as both an anode and cathode for the production of formate and hydrogen from wood-extracted sugar solutions. At 2.1 V, it reaches a 300 mA current density, converting mixed sugars to formate with a 74% yield and producing hydrogen at 104 mL cm2 h-1 with near 100% Faradaic efficiency.

Surfactant Directionally Assembled at the Electrode-Electrolyte Interface for Facilitating Electrocatalytic Aldehyde Hydrogenation

Electrocatalytic hydrogenation of unsaturated aldehydes to unsaturated alcohols is a promising alternative to conventional thermal processes. Both the catalyst and electrolyte deeply impact the performance. Designing the electrode-electrolyte interface remains challenging due to its compositional and structural complexity. Here, we employ the electrocatalytic hydrogenation of 5-hydroxymethylfurfural (HMF) as a reaction model. The typical cationic surfactant, cetyltrimethylammonium bromide (CTAB), and its analogs are employed as electrolyte additives to tune the interfacial microenvironment, delivering high-efficiency hydrogenation of HMF and inhibition of the hydrogen evolution reaction (HER). The surfactants experience a conformational transformation from stochastic distribution to directional assembly under applied potential. This oriented arrangement hampers the transfer of water molecules to the interface and promotes the enrichment of reactants. In addition, near 100 % 2,5-bis(hydroxymethyl)furan (BHMF) selectivity is achieved, and the faradaic efficiency (FE) of the BHMF is improved from 61 % to 74 % at -100 mA cm-2. Notably, the microenvironmental modulation strategy applies to a range of electrocatalytic hydrogenation reactions involving aldehyde substrates. This work paves the way for engineering advanced electrode-electrolyte interfaces and boosting unsaturated alcohol electrosynthesis efficiency.

Manipulating Dual-Metal Catalytic Activities toward Organic Upgrading in Upcycling Plastic Wastes with Inhibited Oxygen Evolution

Electrorefinery of polybutylene terephthalate (PBT) waste plastic, specifically conversion of a PBT-derived 1,4-butanediol (BDO) monomer into value-added succinate coupled with H2 production, emerges as an auspicious strategy to mitigate severe plastic pollution. Herein, we report the synthesis of Mn-doped NiNDA nanosheets (NDA: 2,6-naphthalenedicarboxylic acid), a metal-organic framework (MOF) through a ligand exchange method, and its utilization for electrocatalytic BDO oxidation to succinate. Interestingly, the transformation of doped layered-hydroxide (d-LH) precursors to MOF promotes BDO oxidation while hindering the competitive oxygen evolution reaction. Experimental and theoretical results indicate that the MOF has a higher affinity (i.e., alcoholophilic) for BDO than the d-LH, while Mn doping into NiNDA results in electron accumulation at Ni sites with an upward shift in the d-band center and convenient spin-dependent charge transfer, which are all beneficial for BDO oxidation. The as-constructed two-electrode membrane-electrode assembly (MEA) flow cell, by coupling BDO oxidation and hydrogen evolution reaction, attains an industrial current density of 1.5 A cm-2@1.82 V at 50 °C, corresponding to a specific energy consumption of 3.68 kWh/Nm3 H2. This represents an energy saving of >25% for hydrogen production on an industrial scale compared to conventional water electrolysis (∼5 kWh/Nm3 H2) in addition to the production of valuable chemicals.

Construction of an electron-transfer channel via Cu-O-Ni to inhibit the overoxidation of Ni for durable methanol oxidation at industrial current density

The electrocatalytic methanol oxidation reaction (MOR) is a viable approach for realizing high value-added formate transformation from biomass byproducts. However, usually it is restricted by the excess adsorption of intermediates (COad) and overoxidation of catalysts, which results in low product selectivity and inactivation of the active sites. Herein, a novel Cu-O-Ni electron-transfer channel was constructed by loading NiCuO x on nickel foam (NF) to inhibit the overoxidation of Ni and enhance the formate selectivity of the MOR. The optimized NiCuO x -2/NF demonstrated excellent MOR catalytic performance at industrial current density (E 500 = 1.42 V) and high faradaic efficiency of ∼100%, as well as durable formate generation up to 600 h at ∼500 mA cm-2. The directional electron transfer from Cu to Ni and enhanced lattice stability could alleviate the overoxidation of Ni(iii) active sites to guarantee reversible Ni(ii)/Ni(iii) cycles and endow NiCuO x -2/NF with high stability under increased current density, respectively. An established electrolytic cell created by coupling the MOR with the hydrogen evolution reaction could produce H2 with low electric consumption (230 mV lower voltage at 400 mA cm-2) and concurrently generated the high value-added product of formate at the anode.

Energy-Saving Electrochemical Hydrogen Production Coupled with Biomass-Derived Isobutanol Upgrading

The widespread application of electrochemical hydrogen production faces significant challenges, primarily attributed to the high overpotential of the oxygen evolution reaction (OER) in conventional water electrolysis. To address this issue, an effective strategy involves substituting OER with the value-added oxidation of biomass feedstock, reducing the energy requirements for electrochemical hydrogen production while simultaneously upgrading the biomass. Herein, we introduce an electrocatalytic approach for the value-added oxidation of isobutanol, a high energy density bio-fuel, coupled with hydrogen production. This approach offers a sustainable route to produce the valuable fine chemical isobutyric acid under mild condition. The electrodeposited Ni(OH)2 electrocatalyst exhibits exceptional electrocatalytic activity and durability for the electro-oxidation of isobutanol, achieving an impressive faradaic efficiency of up to 92.4 % for isobutyric acid at 1.45 V vs. RHE. Mechanistic insights reveal that side reactions predominantly stem from the oxidative C-C cleavage of isobutyraldehyde intermediate, forming by-products including formic acid and acetone. Furthermore, we demonstrate the electro-oxidation of isobutanol coupled with hydrogen production in a two-electrode undivided cell, notably reducing the electrolysis voltage by approximately 180 mV at 40 mA cm-2. Overall, this work represents a significant step towards improving the cost-effectiveness of hydrogen production and advancing the conversion of bio-fuels.

Molybdenum, tungsten doped cobalt phosphides as efficient catalysts for coproduction of hydrogen and formate by glycerol electrolysis

H2 and formate are important energy carriers in fuel-cells and feedstocks in chemical industry. The hydrogen evolution reaction (HER) coupling with electro-oxidative cleavage of thermodynamically favorable polyols is a promising way to coproduce H2 and formate via electrochemical means, highly active catalysts for HER and electrooxidative cleavage of polycols are the key to achieve such a goal. Herein, molybdenum (Mo), tungsten (W) doped cobalt phosphides (Co2P) deposited onto nickel foam (NF) substrate, denoted as Mo-Co2P/NF and W-Co2P/NF, respectively, were investigated as catalytic electrodes for HER and electrochemical glycerol oxidation reaction (GOR) to yield H2 and formate. The W-Co2P/NF electrode exhibited low overpotential (η) of 113 mV to attain a current density (J) of -100 mA cm-2 for HER, while the Mo-Co2P/NF electrode demonstrated high GOR efficiency for selective production of formate. In situ Raman and infrared spectroscopic characterizations revealed that the evolved CoO2 from Co2P is the genuine catalytic sites for GOR. The asymmetric electrolyzer based on W-Co2P/NF cathode and Mo-Co2P/NF anode delivered a J = 100 mA cm-2 at 1.8 V voltage for glycerol electrolysis, which led to 18.2 % reduced electricity consumption relative to water electrolysis. This work highlights the potential of heteroelement doped phosphide in catalytic performances for HER and GOR, and opens up new avenue to coproduce more widespread commodity chemicals via gentle and sustainable electrocatalytic means.