Design and Synthesis of FeOOH/CeO2 Heterolayered Nanotube Electrocatalysts for the Oxygen Evolution Reaction

Interfacial engineering layered bimetallic oxyhydroxides for efficient oxygen evolution reaction

Transition metal-based oxyhydroxides (MOOH) have garnered significant attention as promising catalyst for the Oxygen Evolution Reaction (OER). However, the direct synthesis of MOOH poses challenges due to the instability of trivalent cobalt and nickel salts, attrivuted to their high oxidation states. In this study, theoretical computations predicted that Co(OH)2 nanosheets are exclusively formed on carbon structures, owing to the stronger binding energy between CoOOH and CC compared to Co(OH)2. Furthermore, the presence of FeOOH interface reduces the binding energy between CoOOH and carbon structure. Experiment evidence confirms that CoOOH can be directly synthesized through controlled epitaxial growth on an FeOOH interface using a hydrothermal method. Moreover, the in-situ doping of iron leads to the formation of high-quality Fe0.35Co0.65OOH with exceptional OER performance, displaying a low overpotential of 240 mV at 10 mA cm-2 and a small Tafel slope of 43 mV dec-1. Density functional theory (DFT) calculations uncover the substantial enhancement of oxygen-containing species adsorption abilities by Fe0.35Co0.65OOH, resulting in improved OER activity. This work presents a promising strategy for the efficient preparation of layered cobalt oxyhydroxides, enabling efficient energy conversion and storage.

CeO2 for modulating the electronic structure of nickel-cobalt bimetallic phosphides to promote efficient overall water splitting

The discovery of earth-abundant electrocatalysts to replace platinum and iridium for overall water splitting is a crucial step in reducing the cost of green hydrogen production. Transition metal phosphides have drawn wide attention due to their non-toxicity, good chemical stability, low cost, and stable catalytic activity in alkaline electrolytes. We report a three-dimensional flower-like structure composed of core-shell nanoneedles as catalysts, in which CeO2 is introduced on the surface of nickel cobalt bimetallic phosphide through electrodeposition. And X-ray photoelectron spectroscopy testing and DFT calculations show electron coupling and transfer between CeO2 and CoP3, thereby modulating the electronic structure of the catalyst surface and reducing the adsorption energy of H atoms during the catalytic process, resulting in enhanced catalytic activity. In 1 M KOH, it exhibits a low overpotential of 109 and 296 mV to achieve the current density of 50 mA cm-2 for HER and OER, respectively. When used as both cathode and anode as a bifunctional catalyst, a voltage of only 1.77 V is required to achieve a current density of 50 mA cm-2, demonstrating great industrial potential.

Designing transition metal-based porous architectures for supercapacitor electrodes: a review

Over the past decade, transition metal (TM)-based electrodes have shown intriguing physicochemical properties and widespread applications, especially in the field of supercapacitor energy storage owing to their diverse configurations, composition, porosity, and redox reactions. As one of the most intriguing research interests, the design of porous architectures in TM-based electrode materials has been demonstrated to facilitate ion/electron transport, modulate their electronic structure, diminish strain relaxation, and realize synergistic effects of multi-metals. Herein, the recent advances in porous TM-based electrodes are summarized, focusing on their typical synthesis strategies, including template-mediated assembly, thermal decomposition strategy, chemical deposition strategy, and host-guest hybridization strategy. Simultaneously, the corresponding conversion mechanism of each synthesis strategy are reviewed, and the merits and demerits of each strategy in building porous architectures are also discussed. Subsequently, TM-based electrode materials are categorized into TM oxides, TM hydroxides, TM sulfides, TM phosphides, TM carbides, and other TM species with a detailed review of their crystalline phase, electronic structure, and microstructure evolution to tune their electrochemical energy storage capacity. Finally, the challenges and prospects of porous TM-based electrode materials are presented to guide the future development in this field.

The role of reducibility vis-à-vis oxygen vacancies of doped Co3O4/CeO2 in the oxygen evolution reaction

Electrochemical water splitting, which is a highly promising and environmentally friendly technology for H2 fuel production, faces significant hurdles due to the sluggish kinetics of the oxygen evolution reaction. Co -based oxides have garnered significant attention as alternative catalysts for the oxygen evolution reaction owing to the Co2+/Co3+ redox couple. Enhancing the challenging Co2+ → Co3+ oxidation process can further improve the catalytic oxygen evolution reaction. The aim of our work was to design a Co3O4-based catalyst to enhance reactivity by increasing the number of Co3+ active sites, serving as an excellent platform for facilitating the oxygen evolution reaction. To drive the effectiveness of the catalyst, in this study, we synthesized Co3O4 anchored on CeO2 (Co3O4/CeO2). The kinetics and efficacy of the oxygen evolution reaction catalysed by Co3O4/CeO2 was significantly improved by aliovalent doping of Sr into Ce sites and Cu into Co sites. The reducible nature of Ce stimulates the formation of Co3+ ions, resulting in an increased production of intermediate -OOH species, thus expediting the reaction. The transformation of Co2+ to Co3+ consequently leads to an increase in anion vacancies, which, in turn, promotes the adsorption of more intermediate species at the active site. The Sr- and Cu-doped Co3O4/CeO2 catalyst exhibited a high current density of 200 mA cm-2 at 580 mV and a low overpotential of 297 mV at 10 mA cm-2. The study functions as a key indicator to establish a connection between oxygen vacancies and metal oxidation states in order to investigate the mechanistic aspects of the oxygen evolution reaction on mixed metal oxides. Moreover, this study is expected to pave the way for the development of innovative oxygen evolution reaction catalysts with reducible supports, thus offering a new pathway for their design.

A motif for B/O-site modulation in LaFeO3 towards boosted oxygen evolution

Here, a series of transition metal (Ni) doped iron-based perovskite oxides LaFe1-xNixO3-δ (x = 0, 0.25, 0.5, 0.75, 1) were prepared, and then the perovskite oxide with the optimized nickel-iron ratio was doped with non-metallic elements (N). Experimental and theoretical investigations reveal that the co-doping breaks the traditional linear constraint relationship (GOOH - GOH = 3.2 eV) and the theoretical overvoltage is reduced from 0.64 V (LaFeO3-δ) to 0.44 V (LaFe0.5Ni0.5O3-δ/N). Specifically, Ni-doping can accelerate electron transfer and improve the conductivity. Moreover, N-doping can reduce the adsorption energy of *OH/*O and enhance the adsorption energy of *OOH. We demonstrated that the optimized cation and anion co-doped LaFe0.5Ni0.5O3-δ/N perovskite oxide exhibits an excellent OER performance, with a low overpotential of 270.6 mV at 10 mA cm-2 and a small Tafel slope of 65 mV dec-1 in 1 M KOH solution, markedly exceeding that of the parent perovskite oxide LaFeO3-δ (300.9 mV) and commercial IrO2 (289.1 mV). It also delivers decent durability with no significant degradation after a 35 h stability test. This work reveals the internal mechanism of perovskite oxide by doping cation and anion for water oxidation, which broadens the idea for the rational design of new perovskite-based sustainable energy catalysts.

Ce Hydroxide-Interfaced NiFe Sulfide Electrocatalyst with Improved Performance for the Oxygen Evolution Reaction

The development of electrochemically inexpensive, durable, and active electrocatalysts for the oxygen evolution reaction (OER) is attracting considerable attention. The heterogeneous interfacing might regulate the electronic structure and further improve the electrochemical activity. Herein, a Ce(OH)3 nanoparticle-interfaced Fe-doped nickel sulfide (Ce(OH)3@Fe-Ni3S2) electrocatalyst was prepared to improve the OER performance. The fabricated electrocatalyst displayed excellent intrinsic activity and long-term stability in 1 M KOH for the OER. The catalyst shows an ultralow overpotential of 195 mV at a current density of 10 mA cm-2 and a Tafel slope of 52 mV dec-1, which are remarkably smaller than those of the control samples. This excellent electrocatalytic activity is attributed to the incorporation of Ce(OH)3 nanoparticles on the surface of the Fe-Ni3S2 nanosheet, which increases the electrochemical activity and enlarges the active surface area of the catalyst. In comparison to previous nonprecious OER electrocatalysts, the prepared Ce(OH)3@Fe-Ni3S2 exhibits greater electrocatalytic activity and longer durability, allowing for the selection of new electrocatalysts for practical applications.

Boosting Electrochemical Nitrogen Fixation via Regulating Surface Electronic Structure by CeO2 Hybridization

Electrocatalytic nitrogen reduction reaction (NRR) paves a sustainable way to produce NH3 but suffering from the relatively low NH3 yield and poor selectivity. High-performance NRR catalysts and a deep insight into the structure-performance relationship are higher desired. Herein, a molten-salt approach is developed to synthesize tiny CeO2 nanoparticles anchored by ultra-thin MoN nanosheets as advanced catalysts for NRR. Specifically, a considerably high NH3 yield rate of 27.5 µg h-1  mg-1 with 17.2% Faradaic efficiency (FE) can be achieved at -0.3 V vs (RHE) under ambient conditions. Experimental and density functional theory (DFT) calculations further point out that the incorporation of MoN with CeO2 can promotes the enlargement of the electron deficient area of nitrogen vacancy site. The enlarged electron deficient area contributes to the accommodation of lone pair electrons of N2 , which dramatically improves the N2 adsorption/activation and the key intermediates (*NNH and *NH3 ) generation, thus boosting the NRR performance.

Macroscopic Spontaneous Piezopolarization and Oxygen-Vacancy Coupled Robust NaNbO3/FeOOH Heterojunction for Pharmaceutical Drug Degradation and O2 Evolution: Combined Experimental and Theoretical Study

Prompt recombination of photoproduced charges in bulk and surface of a photocatalyst significantly impedes catalytic efficiency. To address these challenges, FeOOH nanorods (NRs) anchored NaNbO3 (NNO) piezoelectric microcubes (MCs) have been fabricated for ciprofloxacin (CIP) degradation and oxygen evolution through water splitting by coupling macroscopic spontaneous piezoelectric polarization and a built-in electric field. The local electric field induced by surface oxygen vacancies (Ovs) and orientation of FeOOH NRs over NNO MCs afford the polarization electric field a significant boost, driving the quick separation/migration of charge carriers from bulk to the surface. The polarized NNO/FeOOH composite with ample Ovs demonstrates an outstanding piezophotocatalytic CIP degradation of 93% in 1 h, higher than pristine materials (NNO and FeOOH), and a high O2 evolution rate of 1155 μmol h-1. The effect of piezoelectric polarization on the catalytic activity is supplemented by theoretical simulations. This work offers an avenue for selective pollutant remediation and water splitting through the rational design of piezoelectric polarization-mediated heterostructure systems with surface Ovs.

Single-atom catalysts supported on a hybrid structure of boron nitride/graphene for efficient nitrogen fixation via synergistic interfacial interactions

Hexagonal boron nitride (BN) shows significant chemical stability and promising thermal nitrogen reduction reaction (NRR) activity but suffers from low conductivity in electrolysis with a wide band gap. To overcome this problem, two-dimensional (2D) BN and graphene (G) are designed as a heterostructure, namely BN/G. According to density functional theory (DFT), the higher conductivity of G narrows the band gap of BN by inducing some electronic states near the Fermi energy level (Ef). Once transition metals (TMs) are anchored in the BN/G structure as single atom catalysts (SACs), the NRR activity improves as the inert BN basal layer activates with moderate *NH2 binding energy and further the band gap is reduced to zero. V (vanadium) and W (tungsten) SACs exhibit the best performance with limiting potentials of -0.22 and -0.41 V, respectively. This study helps in understanding the improvement of the NRR activity of BN, providing physical insights into the adsorbate-TM interaction.

Highly Efficient and Stable Mo-CoP3 @FeOOH Electrocatalysts for Alkaline Seawater Splitting

The introduction of high-valence state elements and highly active species is promisingly desired to design superior electrocatalysts for water electrolysis. Exploring scalable synthetic strategies is necessary for an in-depth understanding of the mechanism of improving electrocatalytic performance. But it remains challenging. Herein, several electrocatalysts through element doping are prepared. The obtained Mo-CoP3 -2@FeOOH samples show the overpotentials (OER) of 232 mV (alkaline seawater) and 262 mV (KOH electrolyte). As HER catalyst, it also presents an excellent electrocatalytic performance. The above electrocatalysts are utilized as anode/cathode to assemble devices for alkaline seawater/water electrolysis, which delivers a cell voltage of 1.58 V and durability of 350 h. Density functional theory calculations reveal that Mo ion doping and FeOOH significantly enhance the density states of the Fermi level and tune the position of the d-band center. It expedites the charge transfer and decreases the adsorption energy of intermediates. It demonstrates that transition-metal phosphides coated with highly active FeOOH offer an effective route to fabricate high-performance and durable catalysts for seawater/water electrolysis.

Ni-modified FeOOH integrated electrode by self-source corrosion of nickel foam for high-efficiency electrochemical water oxidation

The construction and application of efficient iron oxyhydroxide (FeOOH) is still a challenge in the field of energy conversion. Here, a facile preparation method is developed by directly utilizing commercialized nickel foams (NF) as the nickel source and the supporting framework, as well as the ingenious use of etching effect originating from acidic medium in the process of iron salt hydrolysis. As a result, a Ni-modulated FeOOH integrated electrode (Ni-FeOOH/NF) is obtained. Unexpectedly, the implementation of our scheme effectively activates the catalytic intrinsic activity of FeOOH, successfully transforming the inert NF into an integrated electrode with high oxygen evolution reaction (OER) performance. Specifically, the Ni-FeOOH/NF exhibits the overpotential of 277 mV (@100 mA cm-2) and superior stability for OER. Additionally, the as-prepared Ni-FeOOH/NF electrode could also operate steadily for OER in alkaline adjusted saline water. Our research provides a new idea for the preparation of satisfactory Fe-based metal materials as OER electrocatalysts.

In situ growth of NiCo-MOF and the derived NiCo2O4/NiCo2O4/Ni foam composite with a wire-penetrated-cage hierarchical architecture for an efficient oxygen evolution reaction

A NiCo2O4/NiCo2O4/Ni foam (NCO/NCO/NF) hybrid composite with a wire-penetrated-cage hierarchical structure was synthesized by in situ growth of bimetallic NiCo metal-organic frameworks (NiCo-MOF) on a NiCo layered double hydroxide (NiCo-LDH) nanowire-modified Ni foam (NF) surface and subsequent heat treatment in air. The NCO/NCO/NF hybrid composite shows higher specific surface area and more active sites than its individual components. The wire-penetrated-cage hierarchical structure of NCO/NCO/NF and the synergistic coupling of NCO hollow nanocages (NCO HNCs), NCO nanowires (NCO NWs) and NF provide a fast electron transfer path, improve the conductivity, accelerate the kinetic reaction rate, and enhance the structural stability. When assessed as an electrode for the oxygen evolution reaction (OER), the NCO/NCO/NF hybrid composite exhibits a low overpotential of 310 mV at 10 mA cm-2 and current density retention of 91% after a 100 h oxidation reaction, which indicates that it has excellent catalytic activity and durability in the electrocatalytic OER.

Controlled synthesis of M doped NiVS (M = Co, Ce and Cr) as a robust electrocatalyst for urea electrolysis

Urea electrolysis can be used to treat wastewater containing urea and alleviate the energy crisis, so it is one of the best ways to solve environmental and energy problems. This paper reports the synthesis of M doped NiVS (M = Co, Ce and Cr) composites by a simple hydrothermal process for the first time. What is noteworthy is that the Ce-NiVS material as a catalytic electrode requires only 141 mV overpotential for the hydrogen evolution reaction (HER) and 1.291 V potential for the urea oxidation reaction (UOR) at a current density of 10 mA cm-2 in 1.0 M KOH and 0.5 M urea mixed alkaline solution. Using Ce-NiVS/NF as both the anode and cathode for urea electrolysis, a current density of 10 mA cm-2 is driven by a voltage of only 1.55 V, which is better than most previous catalysts. Experimental results demonstrate that the excellent catalytic activity of Ce-NiVS materials is due to the formation of a large number of active sites and the improvement of conductivity due to doping with Ce. Density functional theory calculation shows that the VS4 material has a small Gibbs free energy of hydrogen adsorption, which plays a major role in the hydrogen production process, and Ce-NiS has a higher density of states (DOS) near the Fermi level, indicating that Ce-NiS has better electronic conductivity. The synergistic catalysis of VS4 and Ce-NiS promoted the hydrogen production performance of the Ce-NiVS material. This work provides guidance for the optimization and design of low-cost electrocatalysts to replace expensive precious metal-based electrocatalysts for overall urea electrolysis.

Multifunctional Ni3S2@NF-based electrocatalysts for efficient and durable electrocatalytic water splitting

Transition-metal sulfides (TMSs) have indeed drawn dramatic interest as a potential species of electrocatalysts by virtue of their unique structural features. However, their poor stability and inherent activity have impeded their use in electrocatalytic water splitting. Here, we provide a rational design of a hierarchical nanostructured electrocatalyst containing CeOx-decorated NiCo-layered double hydroxide (LDH) coupled with Ni3S2 protrusions formed on a Ni foam (NF). Specifically, the as-prepared electrocatalyst, denoted as Ni2Co1 LDH-CeOx/Ni3S2@NF, presents only 250 and 300 mV overpotential at ±100 mA cm-2, respectively, along with the Tafel slope values of 92 and 52 mV dec-1, as well remarkable long-term life for water splitting in an alkaline electrolyte. Based on systematic experiments and theoretical analysis, the superior electrocatalytic property in terms of Ni2Co1 LDH-CeOx/Ni3S2@NF can be imputed to the following reasons: the porous framework of Ni3S2@NF provides a largely surface area and high conductivity; the NiCo LDH nanosheets provide enriched active sites and favorable adsorption ability; the oxygen-vacancy-rich CeOx optimizes the electronic configuration. Overall, these factors work synergistically to expedite the catalytic kinetics of splitting water. Our work concentrates on a rational interface to devise efficient, multifunctional, and serviceable electrocatalysts for future applications.

Synergistically Coupled Ni/CeOx@C Electrocatalysts for the Hydrogen Evolution Reaction: Remarkable Performance to Pt/C at High Current Density

Incredibly active electrocatalysts comprising earth-abundant materials that operate as effectively as noble metal catalysts are essential for the sustainable generation of hydrogen through water splitting. However, the vast majority of active catalysts are produced via complicated synthetic processes, making scale-up considerably tricky. In this work, a facile strategy is developed to synthesize superhydrophilic Ni/CeO_x nanoparticles (NPs) integrated into porous carbon (Ni/CeO_x@C) by a simple two-step synthesis strategy as efficient hydrogen evolution reaction (HER) electrocatalysts in 1.0 M KOH. Benefiting from the electron transport induced by the heterogeneous interface between Ni and CeO_x NPs and the superhydrophilic structure of the catalyst, the resultant Ni₂Ce₁@C/500 catalysts exhibit a low overpotential of 26 and 184 mV at a current density of 10 and 300 mA cm^-2, respectively, for HER with a small Tafel slope of 62.03 mV dec^-1 and robust durability over 300 h, and its overpotential at a high current density is much better than the benchmark commercial Pt/C. Results revealed that the electronic rearrangement between Ni and CeO_x integrated into porous carbon could effectively regulate the local conductivity and charge density. In addition, the oxygen vacancies and Ni/CeO_x heterointerface promote water adsorption and hydrogen intermediate dissociation into H₂ molecules, which ultimately accelerate the HER reaction kinetics. Notably, the electrochemical results demonstrate that structural optimization by regulating synthesis temperature and metal concentration could improve the surface features contributing to high electrical conductivity and increase the number of electrochemically active sites on the Ni/CeO_x@C heterointerface, high crystal purity, and better electrical conductivity, resulting in its exceptional electrocatalytic performance toward the HER. These results indicated that the Ni/CeO_x@C electrocatalyst has the potential for practical water-splitting applications because of its controlled production strategy and outstanding Pt-like HER performance.

In-situ growth of 3D hierarchical γ-FeOOH/Ni3S2 heterostructure as high performance electrocatalyst for overall water splitting

Obtaining efficient, stable, and low-cost electrocatalysts is the key to realizing large-scale water splitting. In this work, three-dimensional (3D) hierarchical γ-iron oxyhydroxide (γ-FeOOH)/Ni₃S₂ electrocatalyst on Ni foam is constructed for electrochemical overall water splitting. The 3D γ-FeOOH/Ni₃S₂ heterostructure can effectively enhance active sites and charge transfer capability, also the heterostructure can benefit electronic effect at the interfaces and synergistic effect of multiple components. Therefore, the γ-FeOOH/Ni₃S₂ exhibits excellent electrocatalytic activity with low overpotentials of 279 mV at 50 mA⋅cm^-2 for oxygen evolution reaction and 92 mV at 10 mA⋅cm^-2 for hydrogen evolution reaction, respectively. In addition, only a potential of 1.66 V is needed to attain 10 mA⋅cm^-2 for the overall water splitting. In particular, the γ-FeOOH/Ni₃S₂ exhibits long-term stability for 120 h at 10 mA⋅cm^-2 without significant degradation. This work provides a valuable idea for obtaining low-cost and high performance bifunctional electrocatalysts for water splitting.

Boosting oxygen evolution electrocatalysis via CeO2 engineering on Fe2N nanoparticles for rechargeable Zn-air batteries

In the process of developing low-cost and high-performance bifunctional electrocatalysts, rational selection of catalytic components and tuning of their electronic structures to achieve synergistic effects is a feasible approach. In this work, CeO₂ was composited into Fe/N-doped carbon foam by a molten salt method to improve the electrocatalytic performance of the composite catalyst for the oxygen evolution reaction (OER). The results showed that the excitation of oxygen vacancies in CeO₂ accelerated the migration of oxygen species and enhanced the oxygen storage/release capacity of the as-prepared catalyst. Meanwhile, the size effect of CeO₂ particles enabled the timely discharge of gas bubbles from the reaction system and thus improved the OER kinetics. In addition, a large number of pyridine-N species were induced by CeO₂-doping and sequentially anchored in the carbon matrix. As a result, the Fe₂N active state was formed through the strengthened binding of Fe-N elements. Benefiting from the strong electronic interaction between Fe₂N and CeO₂ components, the optimal CeO₂-Fe₂N/NFC_-2 catalyst sample showed a good OER performance (E_j=10 = 266 mV) and ORR electrocatalytic activity (E_1/2 = 0.87 V). The practical feasibility tests indicated that the Zn-air battery assembled by the CeO₂-Fe₂N/NFC_-2 catalyst exhibited a large energy density and an excellent long-term cycling stability.

Ce Site in Amorphous Iron Oxyhydroxide Nanosheet toward Enhanced Electrochemical Water Oxidation

Iron oxyhydroxide has been considered an auspicious electrocatalyst for the oxygen evolution reaction (OER) in alkaline water electrolysis due to its suitable electronic structure and abundant reserves. However, Fe-based materials seriously suffer from the tradeoff between activity and stability at a high current density above 100 mA cm^-2 . In this work, the Ce atom is introduced into the amorphous iron oxyhydroxide (i.e., CeFeO_x H_y ) nanosheet to simultaneously improve the intrinsic electrocatalytic activity and stability for OER through regulating the redox property of iron oxyhydroxide. In particular, the Ce substitution leads to the distorted octahedral crystal structure of CeFeO_x H_y , along with a regulated coordination site. The CeFeO_x H_y electrode exhibits a low overpotential of 250 mV at 100 mA cm^-2 with a small Tafel slope of 35.1 mVdec^-1 . Moreover, the CeFeO_x H_y electrode can continuously work for 300 h at 100 mA cm^-2 . When applying the CeFeO_x H_y nanosheet electrode as the anode and coupling it with the platinum mesh cathode, the cell voltage for overall water splitting can be lowered to 1.47 V at 10 mA cm^-2 . This work offers a design strategy for highly active, low-cost, and durable material through interfacing high valent metals with earth-abundant oxides/hydroxides.

Lamella-heterostructured nanoporous bimetallic iron-cobalt alloy/oxyhydroxide and cerium oxynitride electrodes as stable catalysts for oxygen evolution

Developing robust nonprecious-metal electrocatalysts with high activity towards sluggish oxygen-evolution reaction is paramount for large-scale hydrogen production via electrochemical water splitting. Here we report that self-supported laminate composite electrodes composed of alternating nanoporous bimetallic iron-cobalt alloy/oxyhydroxide and cerium oxynitride (FeCo/CeO_2-xN_x) heterolamellas hold great promise as highly efficient electrocatalysts for alkaline oxygen-evolution reaction. By virtue of three-dimensional nanoporous architecture to offer abundant and accessible electroactive CoFeOOH/CeO_2-xN_x heterostructure interfaces through facilitating electron transfer and mass transport, nanoporous FeCo/CeO_2-xN_x composite electrodes exhibit superior oxygen-evolution electrocatalysis in 1 M KOH, with ultralow Tafel slope of ~33 mV dec^-1. At overpotential of as low as 360 mV, they reach >3900 mA cm^-2 and retain exceptional stability at ~1900 mA cm^-2 for >1000 h, outperforming commercial RuO₂ and some representative oxygen-evolution-reaction catalysts recently reported. These electrochemical properties make them attractive candidates as oxygen-evolution-reaction electrocatalysts in electrolysis of water for large-scale hydrogen generation.

Quantum dot-doped CeOx-NiB with modulated electron density as a highly efficient bifunctional electrocatalyst for water splitting

Development of economical, efficient and durable non-noble metal electrocatalysts for the hydrogen/oxygen evolution reaction (HER/OER) holds great promise, but still faces great challenges. Herein, a strategy of doping metal borides with rare earth metal oxides and introducing silicon carbide (SiC) quantum dots has been explored to develop efficient bifunctional electrocatalysts. A novel electrocatalyst consists of SiC quantum dot-decorated CeO_x-NiB supported on nickel foam via a one-step mild electroless plating reaction (denoted as CeO_x-NiB/SiC@NF). Notably, the modulated electron density of the CeO_x-NiB/SiC@NF electrode significantly boosts the electrochemically active surface area and electron transfer, and optimizes the hydrogen/water absorption free energy, which delivers current densities of 50 mA cm^-2 and 10 mA cm^-2 at overpotentials of only 131 mV and 234 mV for the HER and the OER, respectively. The target electrode requires only 1.43 V to provide 10 mA cm^-2 for overall water splitting in 1.0 M KOH. Moreover, the electrode also exhibits good stability and durability at the industrial-grade current density (0.5-1 A cm^-2). This work provides a new idea for the development of efficient and durable non-precious metal catalysts.

Engineering Z-Scheme FeOOH/PCN with Fast Photoelectron Transfer and Surface Redox Kinetics for Efficient Solar-Driven CO2 Reduction

Solar-driven conversion of carbon dioxide (CO₂) without sacrificial agents offers an attractive alternative in sustainable energy research; nevertheless, it is often retarded by the sluggish water oxidation kinetics and severe charge recombination. To this end, a Z-scheme iron oxyhydroxide/polymeric carbon nitride (FeOOH/PCN) heterojunction, as identified by quasi in situ X-ray photoelectron spectroscopy, is constructed. In this heterostructure, the two-dimensional FeOOH nanorod provides rich coordinatively unsaturated sites and highly oxidative photoinduced holes to boost the sluggish water decomposition kinetics. Meanwhile, PCN acts as a robust agent for CO₂ reduction. Consequently, FeOOH/PCN achieves efficient CO₂ photoreduction with a superior selectivity of CH₄ (>85%), together with an apparent quantum efficiency of 2.4% at 420 nm that outperforms most two-step photosystems to date. This work offers an innovative strategy for the construction of photocatalytic systems toward solar fuel production.

Interface engineering of CeO2 nanoparticle/Bi2WO6 nanosheet nanohybrids with oxygen vacancies for oxygen evolution reactions under alkaline conditions

Because of the interactive combination synergy effect, hetero interface engineering is used way for advancing electrocatalytic activity and durability. In this study, we demonstrate that a CeO₂/Bi₂WO₆ heterostructure is synthesized by a hydrothermal method. Electrochemical measurement results indicate that CeO₂/Bi₂WO₆ displays not only more OER catalytic active sites with an overpotential of 390 mV and a Tafel slope of 117 mV dec^-1 but also durability for 10 h (97.57%). Such outstanding characteristics are primarily attributed to (1) the considerable activities by CeO₂ nanoparticles uniformly distributed on Bi₂WO₆ nanosheets and (2) the plentiful Bi-O-Ce and W-O-Ce species playing the role of strong couples between CeO₂ nanoparticles and Bi₂WO₆ nanosheets and oxygen vacancy existence in CeO₂ nanoparticles, which can improve the electrochemical active surface area (ECSA) and activity, and enhance the conductivity for OERs. This CeO₂/Bi₂WO₆ consists of the heterojunction engineering that can open a modern method of thinking for high effective OER electrocatalysts.

Effect of Cooperative Redox Property and Oxygen Vacancies on Bifunctional OER and HER Activities of Solvothermally Synthesized CeO2/CuO Composites

Herein, we report the synthesis of the CeO₂/CuO composite as a bifunctional oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) electrocatalyst in a basic medium. The electrocatalyst with an optimum 1:1 CeO₂/CuO shows low OER and HER overpotentials of 410 and 245 mV, respectively. The Tafel slopes of 60.2 and 108.4 mV/dec are measured for OER and HER, respectively. More importantly, the 1:1 CeO₂/CuO composite electrocatalyst requires only a 1.61 V cell voltage to split water to achieve 10 mA/cm² in a two-electrode cell. The role of oxygen vacancies and the cooperative redox activity at the interface of the CeO₂ and CuO phases is explained in the light of Raman and XPS studies, which play the determining factor for the enhanced bifunctional activity of the 1:1 CeO₂/CuO composite. This work provides guidance for the optimization and design of a low-cost alternative electrocatalyst to replace the expensive noble-metal-based electrocatalyst for overall water splitting.

Apparent activity and specific activity of lanthanides (La, Ce, Nd) decorated Co-MOF derivatives for electrocatalytic water splitting

Lanthanide (Ln) rare Earth (RE) elements are often used to incorporate and regulate the local coordination environment and electronic configuration of transition metal based electrocatalysts for acquiring improved electrocatalytic performance. But for a given pristine electrode, is a Ln element concentrated more on promoting the apparent activity of original electrode or on enhancing its specific activity? To address this issue, Ln (La, Ce and Nd) decorated ZIF-67 derivative electrodes (Ln/Co/NC) were fabricated following with the detailed experimental testing of apparent activity and specific activity of assembled electrodes. X-ray photoelectron spectroscopy data confirmed that Ce, Nd and La have played their own role in regulating the coordination electronic structure of the surface atoms of the derived Co/NC by forming different types of chemical bonds. Electrochemical (EC) results confirmed that Ce is concentrated more on the apparent activity of derived Co/NC electrode with the smallest overpotential at 50 mA cm^-2(η₅₀), while Nd contributes more to its reaction kinetic property with the smallest value of Tafel slope in alkaline hydrogen evolution reaction process. But for oxygen evolution reaction, all of La, Ce and Nd deteriorate the apparent activity of the pristine Co/NC electrode. Comparatively, La shows a greater ability to modulate the specific activity of Co/NC with a larger electrochemical active surface area normalized current density, while Nd exhibits the best ability to re-establish the properties of reaction centers. This work illustrates the difference influence of La, Ce and Nd on the apparent activity and specific activity of the ZIF-67 derivative Co/NC electrode. It will do some favors in engineering RE elements modified composite electrodes for EC applications.

RE-doped (RE = La, Ce and Er) Ni2P porous nanostructures as promising electrocatalysts for hydrogen evolution reaction

The construction of an efficient non-noble-metal electrocatalyst towards alkaline hydrogen evolution is challenging but in great demand. The fabrication of a porous nanostructure and heteroatom doping are two productive strategies for developing effective electrocatalysts. In this contribution, we report the preparation of La, Ce and Er-doped Ni₂P porous nanostructures through a facile water bath method and phosphorization strategy. The Er-doped Ni₂P porous nanostructure exhibits superb hydrogen evolution reaction (HER) catalytic performance under alkaline conditions with a low cathodic overpotential of 87 mV (10 mA cm^-2, glassy carbon) and a small Tafel slope of 65.4 mV dec^-1. It also displays excellent electrochemical stability in alkaline electrolytes. First-principles density functional theory (DFT) calculations disclosed the mechanism of the alkaline HER catalysis. For pristine Ni₂P, the P site acts as the optimal active site with the Gibbs free energy of H* absorption (ΔG_H*) of 0.48 eV. After La, Ce and Er are doped, respectively, the P site is still the active center of the three doping systems. Notably, the ΔG_H* value is reduced from 0.48 eV to 0.23 eV (P site in La-doped Ni₂P), 0.20 eV (P site in Ce-doped Ni₂P) and 0.18 eV (P site in Er-doped Ni₂P), suggesting that doping with La, Ce and Er atoms plays a crucial role in decreasing the H* absorption energy on optimal P sites and the optimum active site with a smaller ΔG_H* can expedite the charge transfer rate for H* midbody and H₂ generation. This is particularly noticeable for Er doping, which is in accordance with the experimental result.

In Situ Reconstruction NiO Octahedral Active Sites for Promoting Electrocatalytic Oxygen Evolution of Nickel Phosphate

Electrochemical activation strategy is very effective to improve the intrinsic catalytic activity of metal phosphate toward the sluggish oxygen evolution reaction (OER) for water electrolysis. However, it is still challenging to operando trace the activated reconstruction and corresponding electrocatalytic dynamic mechanisms. Herein, a constant voltage activation strategy is adopted to in situ activate Ni₂ P₄ O₁₂ , in which the break of NiONi bond and dissolution of PO₄ ^3- groups could optimize the lattice oxygen, thus reconstructing an irreversible amorphous Ni(OH)₂ layer with a thickness of 1.5-3.5 nm on the surface of Ni₂ P₄ O₁₂ . The heterostructure electrocatalyst can afford an excellent OER activity in alkaline media with an overpotential of 216.5 mV at 27.0 mA cm^-2 . Operando X-ray absorption fine structure spectroscopy analysis and density functional theory simulations indicate that the heterostructure follows a nonconcerted proton-electron transfer mechanism for OER. This activation strategy demonstrates universality and can be used to the surface reconstruction of other metal phosphates.

Modulating Electronic Characteristics of Nickel Molybdate via an Effective Manganese-Doping Strategy to Enhance Oxidative Desulfurization Performance

Modulating the electronic characteristics of catalysts plays a significant role in optimizing their catalytic activity. Herein, Mn-doped nickel molybdate (MNMO) nanorods are synthesized via replacing the partial Ni sites by the Mn element, engineering a bimetallic synergistic effect to enhance the activation of oxygen (O₂). Compared with the extremely low catalytic activity of pristine nickel molybdate (NiMoO₄), complete desulfurization can be achieved by MNMO under the same reaction conditions. Characterization results show that the electronic structure and surface atomic composition of pure NiMoO₄ will be modulated owing to the introduction of Mn atoms, leading to the enhancement of the oxygen vacancy content and stronger O₂ activation capacity. Besides, the optimized catalyst MNMO-20 also displays satisfactory cycle performance, and the sulfur removal of dibenzothiophene still maintains 96.1% after six times of recycling. The distinctive engineering strategy and simple synthesis method provide a new insight in designing and developing oxidative desulfurization catalysts with high stability and effectivity.

Incorporation of CeO2 with Ni-Co mixed metal phosphide boosts electrochemical seawater oxidation performance

Electrochemical seawater oxidation has been regarded as one of the most promising strategies for cost-efficient production of hydrogen from the standpoint of sustainability, but suffers from a competitive chlorine evolution/oxidation reaction. Herein, we report a facile hard templated route to fabricate CeO₂ incorporated Ni-Co mixed metal phosphide embedded in a carbon matrix (CeO₂-Co_2-xNi_xP@C). Benefiting from compositional and structural features, the obtained CeO₂-Co_2-xNi_xP@C possesses remarkably improved OER performance in 1 M KOH (η = 295 mV at 10 mA cm^-2) compared with Co_2-xNi_xP@C. More importantly, the catalytic activity and stability is retained well after changing fresh water to seawater to constitute the working electrolyte. The promotion effect of CeO₂ can be attributed to its unique capability in regulating the surface state of catalysts, contributing to efficient inhibition of chlorine competition.

Expediting hole transfer via surface states in hematite-based composite photoanodes

Regarding the indirect hole transfer route in hematite-based photoelectrodes, the widely accepted viewpoint is that the Fe^IVO states act as a hole transfer medium, while other types of surface states act as recombination centers. Alternatively, it has rarely been reported that the recombining surface states may contribute to the charge transport in modified photoelectrodes. In this study, we employed CoCr layered double hydroxide (LDH)/Fe₂O₃ and CoCr LDH/Zr:Fe₂O₃ as research models to investigate the distinct charge transfer pathways in composite photoanodes. Different from the adverse role of surface states at ∼0.7 V versus the reversible hydrogen electrode (r-SS) in the bare hematite photoelectrodes (Fe₂O₃ or Zr:Fe₂O₃), the r-SS in the composite photoanodes (CoCr LDH/Fe₂O₃ or CoCr LDH/Zr:Fe₂O₃) served as a hole transfer station to induce high-valent Co cations, and the position of r-SS determined the onset potential of the composite photoelectrodes. Moreover, the Fe^IVO states still acted as active intermediates to transport numerous holes to the cocatalyst, which enhanced the charge utilization efficiency at 1.23 V versus the reversible hydrogen electrode (RHE) to a large extent. Besides, a noteworthy fact is that Zr doping increased the number of active Fe^IVO states, which significantly contributed to the enhancement in current density. However, it led to a delayed onset potential because of the positively shifted surface states (r-SS and Fe^IVO). Evidently, the different surface state distributions between Fe₂O₃ and Zr:Fe₂O₃ gave rise to anisotropic charge transfer and recombination behavior in the composite photoanodes. This study gives extensive insight into the hole transfer route in composite photoanodes and reveals the surface state-tuning effects of dopants and cocatalysts, which are significant for a deep understanding of the surface states and optimal design of composite photoanodes via surface state modulation.

Yttrium- and Cerium-Codoped Ultrathin Metal-Organic Framework Nanosheet Arrays for High-Efficiency Electrocatalytic Overall Water Splitting

The construction of low-cost, highly efficient, and stable electrocatalysts is a significant challenge for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, we report a facile strategy to fabricate ultrathin metal-organic framework (MOF) nanosheet arrays doped with two rare-earth elements, Y and Ce, and self-supported on nickel foam (NF) to enhance the HER and OER performance by constructing abundant active sites and bimetallic synergistic effects. The NiYCe-MOF/NF features an ultrathin nanosheet array structure and is uniformly and richly codoped by Y and Ce. When it was explored as both the anode and cathode electrocatalysts for overall water splitting, it achieved 10 mA cm^-2 at 136 and 245 mV for the HER and OER in an alkaline electrolyte, respectively. Notably, an extremely low cell voltage of 1.54 V was required to achieve 100 mA cm^-2 in 1.0 M KOH solution, making it a promising substitute for noble-metal catalysts.

Chemical Transformation Induced Core-Shell Ni2P@Fe2P Heterostructures toward Efficient Electrocatalytic Oxygen Evolution

The oxygen evolution reaction (OER) is a crucial reaction in water splitting, metal-air batteries, and other electrochemical conversion technologies. Rationally designed catalysts with rich active sites and high intrinsic activity have been considered as a hopeful strategy to address the sluggish kinetics for OER. However, constructing such active sites in non-noble catalysts still faces grand challenges. To this end, we fabricate a Ni₂P@Fe₂P core-shell structure with outperforming performance toward OER via chemical transformation of rationally designed Ni-MOF hybrid nanosheets. Specifically, the Ni-MOF nanosheets and their supported Fe-based nanomaterials were in situ transformed into porous Ni₂P@Fe₂P core-shell nanosheets composed of Ni₂P and Fe₂P nanodomains in homogenous dispersion via a phosphorization process. When employed as the OER electrocatalyst, the Ni₂P@Fe₂P core-shell nanosheets exhibits excellent OER performance, with a low overpotential of 238/247 mV to drive 50/100 mA cm^-2, a small Tafel slope of 32.91 mV dec^-1, as well as outstanding durability, which could be mainly ascribed to the strong electronic interaction between Ni₂P and Fe₂P nanodomains stabilizing more Ni and Fe atoms with higher valence. These high-valence metal sites promote the generation of high-active Ni/FeOOH to enhance OER activity.

Zinc-doped ferric oxyhydroxide nano-layer enhances the bactericidal activity and osseointegration of a magnesium alloy through augmenting the formation of neutrophil extracellular traps

Implant-associated infections (IAI) and osseointegration disorders are the most common complications in orthopedics. Studies have shown that neutrophils surrounding implants play a vital role in regulating these complications. Although magnesium (Mg) and its alloys are considered promising biodegradable bone implants, their role in neutrophil-mediated antibacteria has not yet been examined. Considering the rapid corrosion of Mg, it is necessary to develop methods to inhibit its corrosion. To solve these issues, a zinc-doped ferric oxyhydroxide nano-layer modified plasma electrolytic oxidation (PEO)-coated Mg alloy (PEO-FeZn) was developed in this study, and its antibacterial, immune anti-infective, and osteogenic ability were systematically evaluated. The results showed that PEO-FeZn nano-layer enhanced the corrosion resistance, biocompatibility, bactericidal activity, and osteoblastic differentiation activity of the Mg alloy. Moreover, PEO-FeZn nano-layer inhibited immune evasion-related gene expression and contributed to the formation of neutrophil extracellular traps (NETs) by activating the extracellular release of DNA fibers and granule proteins, and thereby suppressing bacterial invasion and promoting osseointegration in vivo in Staphylococcus aureus (S. aureus)-infected rat femurs. Overall, the findings of this study could serve as a reference for the fabrication of highly biocompatible and corrosion resistant Mg alloys to address the challenges of IAI and osseointegration disorders. STATEMENT OF SIGNIFICANCE: The widely used metallic biomaterials usually come with the risk of IAI. As the first responder around the biomaterials, neutrophils could form NETs to defense against microorganism and promote tissue remodeling. Therefore, biomaterials addressing antibacterial and neutrophils-modulatory strategies are highly necessary in reducing IAI. To solve these issues, we grew PEO-FeZn nano-layers in situ on Mg alloy using a simple and green technique. The nano-layer not only enhanced the corrosion resistance and biocompatibility of Mg alloy, but also elevated the antibacterial and osteogenesis capability. Moreover, nano-layer contributed to NETs formation, thereby suppressing bacterial invasion and even promoting osseointegration in S.aureus-infected femurs. Accordingly, this functionalized multilayer coating with antibacterial immunity represents a novel therapeutic strategy for IAI and weak osseointegration.

Synergistic Incorporating RuO2 and NiFeOOH Layers onto Ni3 S2 Nanoflakes with Modulated Electron Structure for Efficient Water Splitting

Synergistic electronic modulations is an effective strategy to develop efficient and stable electrocatalysts for the electrochemical hydrogen production via water splitting. Herein, tremella-like Ni₃ S₂ @RuO₂ and Ni₃ S₂ @NiFeOOH heterostructures catalysts are constructed on Ni foams (NF) by coupling RuO₂ and NiFeOOH on Ni₃ S₂ nanoflake arrays. The resulting Ni₃ S₂ @RuO₂ /NF electrode exhibits top-level hydrogen evolution reaction electrocatalysis with an extremely low overpotential of 12 mV at 10 mA cm^-2 and a Tafel slope of 30.7 mV dec^-1 , as well as the as-obtained Ni₃ S₂ @NiFeOOH/NF electrode with tunable binding energy for OH* intermediates shows remarkable oxygen evolution reaction electrocatalysis with an overpotential of 227 mV at 10 mA cm^-2 . The electrolyzer employing Ni₃ S₂ @RuO₂ /NF electrode for cathodic H₂ production and Ni₃ S₂ @NiFeOOH/NF for anodic O₂ production merely needs a low voltage of 1.47 V to drive 10 mA cm^-2 with excellent durability. The combined theoretical calculation and X-ray photoelectron spectroscopy investigation reveal that heterogeneous configuration can induce electron transfer from Ni₃ S₂ to RuO₂ through NiRu/SRu bonds, and thus tailor the d-band center and optimize the activated H₂ O/H* Gibbs free energies for enhanced hydrogen evolution reaction on Ni₃ S₂ @RuO₂ . This study may shed new light on the construction of heterostructures as highest-performing electrocatalysts and offer unique insight into the theory mechanism.

In Situ Reconstructed Zn doped Fex Ni(1- x ) OOH Catalyst for Efficient and Ultrastable Oxygen Evolution Reaction at High Current Densities

Developing FeOOH as a robust electrocatalyst for high output oxygen evolution reaction (OER) remains challenging due to its low conductivity and dissolvability in alkaline conditions. Herein, it is demonstrated that the robust and high output Zn doped NiOOH-FeOOH (Zn-Fe_x Ni_(1-x) )OOH catalyst can be derived by electro-oxidation-induced reconstruction from the pre-electrocatalyst of Zn modified Ni metal/FeOOH film supported by nickel foam (NF). In situ Raman and ex situ characterizations elucidate that the pre-electrocatalyst undergoes dynamic reconstruction occurring on both the catalyst surface and underneath metal support during the OER process. That involves the Fe dissolution-redeposition and the merge of Zn doped FeOOH with in situ generated NiOOH from NF support and NiZn alloy nanoparticles. Benefiting from the Zn doping and the covalence interaction of FeOOH-NiOOH, the reconstructed electrode shows superior corrosion resistance, and enhanced catalytic activity as well as bonding force at the catalyst-support interface. Together with the feature of superaerophobic surface, the reconstructed electrode only requires an overpotential of 330 mV at a high-current-density of 1000 mA cm^-2 and maintains 97% of its initial activity after 1000 h. This work provides an in-depth understanding of electrocatalyst reconstruction during the OER process, which facilitates the design of high-performance OER catalysts.

Surface Reconstruction of Co4N Coupled with CeO2 toward Enhanced Alkaline Oxygen Evolution Reaction

Constructing the active interface in a heterojunction electrocatalyst is critical for the electron transfer and intermediate adsorption (O*, OH*, and HOO*) in alkaline oxygen evolution reaction (OER) but still remains challenging. Herein, a CeO₂/Co₄N heterostructure is rationally synthesized through the direct calcination of Ce[Co(CN)₆], followed by thermal nitridation. The in situ electrochemically generated CoOOH on the surface of Co₄N serves as the active site for the OER, and the coupled CeO₂ with oxygen vacancy can optimize the energy barrier of intermediate reactions of the OER, which simultaneously boosts the OER performance. Besides, electrochemical measurement results demonstrate that oxygen vacancies in CeO₂ and optimized absorption free energy originating from the electron transfer between CeO₂ and CoOOH contribute to enhanced OER kinetics. This work provides new insight into regulating the interface heterostructure to rationally design efficient OER electrocatalysts under alkaline conditions.

Rare Earth-Based Nanomaterials for Supercapacitors: Preparation, Structure Engineering and Application

Supercapacitors (SCs) can effectively alleviate problems such as energy shortage and serious greenhouse effect. The properties of electrode materials directly affect the performance of SCs. Rare earth (RE) is known as "modern industrial vitamins", and their functional materials have been listed as key strategic materials. In the past few years, the number of scientific reports on RE-based nanomaterials for SCs has increased rapidly, confirming that adding RE elements or compounds to the host electrode materials with various nanostructured morphologies can greatly enhance their electrochemical performance. Although RE-based nanomaterials have made rapid progress in SCs, there are very few works providing a comprehensive survey of this field. In view of this, a comprehensive overview of RE-based nanomaterials for SCs is provided here, including the preparation methods, nanostructure engineering, compounds, and composites, along with their capacitance performances. The structure-activity relationships are discussed and highlighted. Meanwhile, the future challenges and perspectives are also pointed out. This Review can not only provide guidance for the further development of SCs but also arouse great interest in RE-based nanomaterials in other research fields such as electrocatalysis, photovoltaic cells, and lithium batteries.

New bimetallic adsorbent material based on cerium-iron nanoparticles highly selective and affine for arsenic(V)

Bimetallic oxy(hydroxides) have gain great interest in water treatment systems based on adsorption processes. Their high OH groups density, in addition to inheriting the oxides properties make them highly promising adsorbents of anions. In this work, highly affine and selective bimetallic oxyhydroxides of cerium and iron (Ce:Fe-P's) for arsenic(V) were synthesized by implementing an assisted microwave methodology. The Ce:Fe-P's were characterized by various techniques (SEM, FTIR, XRD and XPS) and the As(V) adsorption capacity and kinetics as well as the effect of pH and the presence of coexisting anions were determined. The results showed that Ce:Fe-P's have an outstanding As(V) adsorption capacity (179.8 mg g^-1 at C_e = 3 mg L^-1) even at low concentrations (120 mg g^-1 at C_e = 37 μg L^-1). Moreover, the adsorption equilibrium was reached very fast, just in 3 min, with an adsorption rate of 0.123 mg min^-1, that is, 80% of the initial As(V) concentration of 5 mg L^-1 was removed in the first 3 min. The arsenic adsorption capacity decreased only up to 20% at pH above 7, attributed to electrostatic repulsions due to the adsorbent's pH_PZC, which was 6.8. On the other hand, the arsenic adsorption capacity of Ce:Fe-P's decreased just 21% in the presence of 10 mg L^-1 of each of the following competing anions: F^-, Cl^-, SO₄^2-, NO₃^-, PO₄^3- and CO₃^2-, which usually coincide in contaminated water with As(V). Ce:Fe-P's has proven to be one of the most promising As(V) adsorbent materials reported so far in the literature, because it presented an outstanding adsorption capacity and at the same time a very fast adsorption speed. Furthermore, the pH and the concentration of coexisting anions caused little interference in the adsorption processes. Due to the above, the Ce:Fe-P's is already in the process of intellectual protection.

Metal-organic frameworks as a good platform for the fabrication of multi-metal nanomaterials: design strategies, electrocatalytic applications and prospective

MOF-derived multi-metal nanomaterials are attracting numerous attentions in widespread applications such as catalysis, sensors, energy storage and conversion, and environmental remediation. Compared to the monometallic counterparts, the presence of foreign metal is expected to bring new physicochemical properties, thus exhibiting synergistic effect for enhanced performance. MOFs have been proved as a good platform for the fabrication of polymetallic nanomaterials with requisite features. Herein, various design strategies related to constructing multi-metallic nanomaterials from MOFs are summarized for the first time, involving metal nodal substitution, seed epitaxial growth, ion-exchange strategy, guest species encapsulation, solution impregnation and combination with extraneous substrate. Afterwards, the recent advances of multi-metallic nanomaterials for electrocatalytic applications, including oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), are systematically discussed. Finally, a personal outlook on the future trends and challenges are also presented with hope to enlighten deeper understanding and new thoughts for the development of multi-metal nanomaterials from MOFs.

Coupling LaNiO3 Nanorods with FeOOH Nanosheets for Oxygen Evolution Reaction

Perovskite-based electrocatalysts with compositional flexibility and tunable electronic structures have emerged as one of the promising non-noble metal candidates for oxygen evolution reaction (OER). Here, we propose a heterostructure comprising perovskite oxide (LaNiO3) nanorods and iron oxide hydroxide (FeOOH) nanosheets as an effective electrochemical catalyst for OER. The optimized 0.25Fe-LNO catalyst with an interesting 1D-2D hierarchical structure shows a low overpotential of 284 mV at 10 mA cm−2 and a small Tafel slope of 69 mV dec−1. The enhanced performance can be explained by the synergistic effect between LaNiO3 and FeOOH, resulting in an improved electrochemically active surface area, facilitated charge transfer and the optimized adsorption of OH intermediates.