Materials For Oxygen Evolution Reaction Research Articles

Carbon-Based Composites for Oxygen Evolution Reaction Electrocatalysts: Design, Fabrication, and Application.

The four-electron oxidation process of the oxygen evolution reaction (OER) highly influences the performance of many green energy storage and conversion devices due to its sluggish kinetics. The fabrication of cost-effective OER electrocatalysts via a facile and green method is, hence, highly desirable. This review summarizes and discusses the recent progress in creating carbon-based materials for alkaline OER. The contents mainly focus on the design, fabrication, and application of carbon-based materials for alkaline OER, including metal-free carbon materials, carbon-based supported composites, and carbon-based material core-shell hybrids. The work presents references and suggestions for the rational design of highly efficient carbon-based OER materials.

Constructing quasi‐amorphous cobalt oxyhydroxide nanowires with synergy of anion and cation via ion exchange reconstruction for large-current–density oxygen generation

Deep insight into the synergy between anion and cation aids in the maximization of catalytic activity and the rational exploitation of efficient oxygen-evolving catalysts. However, how to use ion exchange reconstruction to devise highly active and cost-efficient oxygen evolution reaction (OER) catalysts with anion and cation synergies for water electrolysis is rarely reported. Herein, the cobalt triphosphide (CoP3) nanowires are elaborately devised as a component-flexible precatalyst for directing an anodic reconfiguration with Ni cation exchange to construct a highly active and quasi‐amorphous cobalt oxyhydroxide (CoOOH) catalyst integrated with cation (Ni) substitution and oxyanion (PO43-) decoration (denoted by R-(Ni)CoP3). Interestingly, the structural evolution and the Ni cation exchange processes are captured through various in/ex situ techniques. The resultant R-(Ni)CoP3 nanowires display a splendid activity with low overpotentials of 406 and 420 mV to respectively deliver industrial grade current densities of 1000 and 1500 mA cm−2, and an outstanding stability over 300 h at a large current density of 500 mA cm−2, superior to most progressive cobalt-based OER materials and the benchmark IrO2. The combination of theoretical calculations with experimental studies demonstrate that the synergy of cation (Ni) substitution and oxyanion (PO43-) decoration can significantly modulate the electronic states of CoOOH and optimize the adsorption free energy of OER intermediates, thus immensely expediting the kinetics process and enhancing the charge transfer ability and the intrinsic OER activity. This research suggests ion-regulatory reconfiguration as a flexible and changeable strategy to construct various efficient and advanced catalysts for water electrolysis and beyond.

Shock-endurable and reversible evolution between CoOOH and intermediate governed by interfacial strain for fluctuating oxygen evolution

Transition metal oxide usually suffers from reconstruction into metal oxyhydroxide during oxygen evolution reaction (OER), while irreversible evolution between metal oxyhydroxides and intermediate species cannot agilely response to the fluctuating power of renewable energy. Herein, an individual CoMoxO4 phase with a tunable Co/Mo stoichiometry is reconstructed into CoOOH skin as active material for OER. Compressive strain induced by CoMo1.14O4/CoOOH interface, downshifting the d-band center of CoOOH, is an effective strategy to not only accelerate the sluggish kinetics of OER, but also enable inspiring the expeditious evolution and the reversibility between CoOOH and intermediate species. The reversibility is an applicable demand for OER in case of fluctuating potential. Reaction current on CoMo1.14O4 at constant potential is demonstrated by the lower fluctuation of 1.7 %, relative to 13.8 % in CoMoO4 after 12 cycles. Meanwhile, an anion exchange membrane water splitting electrolyzer made of CoMo1.14O4 anode can endure current shock of 50 ∼ 800 mA cm−2 in 0.2 s, which has negligible decay at 800 mA cm−2 after 9 shocks. Designing strategy of interfacial strain modulated by stoichiometry can be universally extended into the other oxide electrocatalysts including NiMoO4 and their derivatives.

Fe2O3 facilitating deeper transformation of Ni-MOF into active NiOOH for enhanced OER performance

Due to the large specific surface area and the highly-exposed active metal centers, nickel metal-organic frameworks (MOFs) have recently emerged as one of the excellent functional materials for oxygen evolution reactions (OER). Herein, we have construct uniformly distributed Fe2O3 particles within Ni-MOF nanosheets (Ni-MOF NSs) for enhanced OER performance. This electrocatalyst, prepared by a facile hydrothermal method, provides highly active Fe2O3 particles while preserving the framework structure of Ni-MOF for effective substrates diffusion. The optimal Fe2O3 doped Ni-MOF NSs deliver high stability in alkaline and exhibit striking OER performance with an overpotential of 232 mV at 10 mA cm−2 and a Tafel slope of 49.3 mV dec−1, outperforming the pristine Ni-MOF and most reported non-noble metal based electrocatalysts. The enhance catalytic activity of Fe2O3 doped Ni-MOF NSs is likely due to the introduction of Fe2O3 particles to facilitate the deeper transformation of Ni-MOF into active NiOOH species.

Silica-Derived Nanostructured Electrode Materials for ORR, OER, HER, CO2RR Electrocatalysis, and Energy Storage Applications: A Review.

Silica-derived nanostructured catalysts (SDNCs) are a class of materials synthesized using nanocasting and templating techniques, which involve the sacrificial removal of a silica template to generate highly porous nanostructured materials. The surface of these nanostructures is functionalized with a variety of electrocatalytically active metal and non-metal atoms. SDNCs have attracted considerable attention due to their unique physicochemical properties, tunable electronic configuration, and microstructure. These properties make them highly efficient catalysts and promising electrode materials for next generation electrocatalysis, energy conversion, and energy storage technologies. The continued development of SDNCs is likely to lead to new and improved electrocatalysts and electrode materials. This review article provides a comprehensive overview of the recent advances in the development of SDNCs for electrocatalysis and energy storage applications. It analyzes 337,061 research articles published in the Web of Science (WoS) database up to December 2022 using the keywords "silica", "electrocatalysts", "ORR", "OER", "HER", "HOR", "CO2RR", "batteries", and "supercapacitors". The review discusses the application of SDNCs for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO2RR), supercapacitors, lithium-ion batteries, and thermal energy storage applications. It concludes by discussing the advantages and limitations of SDNCs for energy applications.

High-spin Co3+ in cobalt oxyhydroxide for efficient water oxidation

Cobalt oxyhydroxide (CoOOH) is a promising catalytic material for oxygen evolution reaction (OER). In the traditional CoOOH structure, Co3+ exhibits a low-spin state configuration (t2g6eg0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${t}_{2{{{{{\\rm{g}}}}}}}^{6}{e}_{{{{{{\\rm{g}}}}}}}^{0}$$\\end{document}), with electron transfer occurring in face-to-face t2g*\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${t}_{2{{{{{\\rm{g}}}}}}}^{*}$$\\end{document} orbitals. In this work, we report the successful synthesis of high-spin state Co3+ CoOOH structure, by introducing coordinatively unsaturated Co atoms. As compared to the low-spin state CoOOH, electron transfer in the high-spin state CoOOH occurs in apex-to-apex eg*\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${e}_{{{{{{\\rm{g}}}}}}}^{*}$$\\end{document} orbitals, which exhibits faster electron transfer ability. As a result, the high-spin state CoOOH performs superior OER activity with an overpotential of 226 mV at 10 mA cm−2, which is 148 mV lower than that of the low-spin state CoOOH. This work emphasizes the effect of the spin state of Co3+ on OER activity of CoOOH based electrocatalysts for water splitting, and thus provides a new strategy for designing highly efficient electrocatalysts.

Facile one-step solid-state synthesis of CuO nanoparticles finely decorated over carbon sheets for improved OER activity

Renewable energy storage and conversion in electrochemical fuel cells require highly efficient and cost-effective noble metal free electrocatalysts for oxygen evolution reaction (OER). Downscaling of a material to nanoscale morphology can lead to enhancement in its surface activities affecting its physical and chemical properties which can well serve the purpose. In lieu to this, it could be one of the first reports to tune the morphology of CuO particles to 10–25 nm finely trapped inside non-graphitic carbon sheets using a novel single step solid state reaction. XRD, SEM, TEM, XPS, and Raman analyses confirm the structural and morphological attributes. The synergistic effect from carbon and copper oxide resulted in the attainment of best-in-class electrode material for oxygen evolution reaction (OER). The as-prepared CuO/C shows an excellent OER activity with a low overpotential of 454 mV (vs. Ag/AgCl) at a current density of 10 mA cm−2 with a low Tafel slope of 74.9 mV dec−1. The amount of carbon is optimized to get optimal performance from the CuO nanopowder.

Construction of Ni2P@NiCo-BLDH nanocomposite with hierarchical porous structure on nickel foam as advanced oxygen evolution electrocatalyst

The fabrication of two-dimensional layered double hydroxides (LDHs) materials still faces great challenges, particularly in achieving precise modulation of lamellar metals and interlayer anions for electrocatalytic oxygen evolution reaction (OER). Herein, a hierarchical porous nanocomposite assembled by foam nickel (NF) supported borate anions incorporated bimetallic NiCo hydrotalcite (NiCo-BLDH) on the surface of nickel phosphide sheets (NF/Ni2P @ NiCo-BLDH) is prepared through the NF in-situ phosphating and electrodeposition approach as an electrocatalyst for achieving superior OER catalysis. In this design, introducing multi-phase and incorporated borate anions into LDHs can regulate their structure and properties, creating unique active sites and enhancing the adsorption efficiency of OH- to effectively improve the OER activity. Remarkably, the NF/Ni2P @ NiCo-BLDH electrode shows a low overpotential of 293 mV at 100 mA cm−2 for OER and a Tafel slope of 108.3 mV dec−1 in a 1.0 M KOH medium, surpassing most previously reported NiCo-based catalysts. Nevertheless, the NF/Ni2P electrode exhibits a lower overpotential for the hydrogen evolution reaction (HER) in a 1.0 M KOH medium compared to the NF/Ni2P @ NiCo-BLDH electrode. This work not only advances the catalytic activity of the NiCo-LDH-based materials in OER but also provides a new idea for large-scale electrocatalytic water splitting applications.

Exploration of anode candidacy of Ni0.2Co2.8O4 and integrated Ni0.2Co2.8O4/MWCNTs in supercapacitor and oxygen evolution reaction

In the current research work, Ni0.2Co2.8O4 and Ni0.2Co2.8/MWCNTs have been synthesized via facile sol-gel and wet impregnation method. The synthesized materials attained the crystalline structures as evident from X-ray diffraction analysis (XRD). The uniform morphology and well dispersion of Ni0.2Co2.8O4 onto MWCNTs was observed via scanning electron microscopy (SEM). The electrochemical investigations for supercapacitor application by cyclic voltammetry (CV), galvanostatic charge discharge (GCD), and electrochemical impedance spectroscopy (EIS) revealed that, among both materials, Ni0.2Co2.8O4/MWCNTs has high specific capacitance (CV; 505.8 Fg-1 at 5 mV/s, GCD; 1598 Fg-1 at 0.5 A/g), greater capacitance retention (85 %) at 1000 cycles and has lower charge transfer resistance (Rct; 3.48 Ω cm2). These findings reflected the potential candidacy of Ni0.2Co2.8O4/MWCNTs to be used as anode material in supercapacitor. Further investigations by CV and linear sweep voltammetry (LSV) for oxygen evolution reaction (OER) activity in 1.0 M KOH showed comparatively low over potential of 340 mV @100 mA/cm2 for the same integrated material. Additionally, the lower Tafel slope (47 mV/dec) and solution resistance authenticated it as an appropriate electrocatalyst for OER in water splitting. The CPE (controlled potential electrolysis) revealed the stability of both materials for OER in water oxidation.

Magnetic field-assisted microbial corrosion construction iron sulfides incorporated nickel-iron hydroxide towards efficient oxygen evolution

Nickel iron (hydroxyl) hydroxide with unique layered structure and controllable composition is widely regarded as typical oxygen evolution reaction (OER) catalysts. Recently, developing top-down approaches to realize the facile preparation of transition metal hydroxide catalyst has received wide attention. Based on the natural microorganism corrosion behavior, this work demonstrates the external magnetic field-assisted microbial corrosion strategy to construct advanced transition metal hydroxide OER catalyst, and the prepared biofilm electrode presents superior OER performance in the existence of magnetic field, which needs an overpotential of 287 ​mV at 100 ​mA ​cm−2. Experimental and theoretical calculations show the applied magnetic field can accelerate sulfate reducing bacteria (SRB) corrosion and chemical corrosion. The additional magnetic field can promote SRB corrosion to produce FeS, which can facilitate the optimization of O intermediate desorption from the NiOOH catalyst during OER process, reducing the reaction energy barrier for O→OOH. The synergistic effect between the nickel-iron oxyhydroxides originated from the accelerated chemical corrosion and FeS produced from the accelerated SRB corrosion interprets the improved OER activity. This work explores the influence of magnetic field on the construction of advanced OER materials, which can provide an effective magnetic field-assisted corrosion engineering strategy, and promote the development of multidisciplinary fields of physics, biology, and emerging energy conversion technologies.

Enhanced electrochemical performance of CuO/NiO/rGO for oxygen evolution reaction

To design the highly active, stable electrocatalyst for oxygen evolution is emerging as challenging task for sustainable energy production. Herein, we fabricated the non-noble CuO/NiO/rGO nanocomposite approached by facile chemical co-precipitation method. The successful formation of binary metal oxide nanocomposite with reduced graphene oxide was confirmed with monoclinic CuO and cubic NiO, which is clearly revealed in the XRD diffraction results. By incorporating the CuO and NiO into the rGO sheets results homogeneous tiny nanoparticles morphology decorated on the graphene sheets which improving interaction among metal nanoparticles and carbon based products. The electrocatalytic performance of resultant binary metal oxide nanocomposite with rGO was investigated in alkaline KOH environment towards oxygen evolution reaction. The 200 mV overpotential was attained at 10 mA/cm2 with smaller 165 mV/dec Tafel value. The elevated electrochemical surface area (ECSA) value of 132.5 cm2 was estimated from cyclic voltammetry analysis of optimized CuO/NiO/rGO electrocatalyst. The electrochemical impedance spectrum of the prepared electrocatalyst shows that the low 0.04 Ω charge transfer resistance is highly desirable to the better conductivity. The prepared CuO/NiO/rGO electrocatalyst stability was verified by chronoamperometry test at low 10 mA/cm2 and exhibited stable performance up to 16 h towards OER. Hence, this work contributes innovative synergistic approach for growth of cost effective binary metal-oxide (CuO/NiO) nanocomposite combined with conductive carbon material for oxygen evolution reaction.

Stabilizing the dissolution kinetics by interstitial Zn cations in CoMoO4 for oxygen evolution reaction at high potential

CoMoO4 (CMO), one kind of transition metal oxides, is a promising precursor material for oxygen evolution reaction (OER). However, Mo cations are potentially dissolved into alkaline electrolyte, usually causing an inevitable collapse of CoMoO4 crystal and an unpredictable activity of the reconstructed materials. In this work, interstitial Zn cations in CoMoO4 distort the MoO4 tetrahedrons, and modulate the dissolution kinetics of Mo cations within an approximate level. Therefore, CMO-0.28-Zn with a concentration of 0.28 for Zn/Co exhibits OER performance with an overpotential of 358 mV at 100 mA cm−2 and Tafel slope of 95.5 mV dec−1. Especially, suitable amount of Zn cations enable avoiding the unexpected dissolution of Co cations at high potential. Thus, the durability of the CMO-0.28-Zn catalyst demonstrates the lower current attenuation of 4.5% relative to 9.1% in CMO-0-Zn catalyst without interstitial Zn after 21 h. This investigation indicates that interstitial cations within transition metal oxides can benefit the design of the robust electrocatalysts.

Spinel‐Type Oxides for Acidic Oxygen Evolution Reaction: Mechanism, Modulation, and Perspective

The development of proton exchange membrane water electrolyzers (PEMWEs) is primarily challenged by the slow and unstable oxygen evolution reaction (OER) at the anode. Thus, the pursuit of low‐cost, highly efficient, and durable electrocatalysts is the foundation for the widespread adoption of PEMWEs. In the past few decades, various types of electrocatalysts are proposed to serve as anode materials for acidic OER, but only a few demonstrate catalytic activity and stability comparable to iridium‐ and ruthenium‐based electrocatalysts. In recent years, some transition‐metal oxides are studied as potential candidates for acidic OER. For instance, spinel‐type oxides, e.g., Co3O4, and corresponding compounds demonstrate promise due to the rich coordination structure of metallic ions and moderate adoption energy for intermedia. In this review, recent advances in spinel‐type oxides for acidic OER are summarized. First, a fundamental understanding of reaction mechanisms for OER in acidic media is introduced. Thereafter, recent progress in rational design principles and optimization strategies for spinel oxides is systematically summarized. Finally, challenges and perspectives for the development of spinel‐based acidic OER electrocatalysts are discussed.

Surface reconstruction of NiFe layered double hydroxides by S2- corrosion for efficient oxygen evolution

Nickel-iron layered double hydroxides (NiFe LDH) are subject to surface reconstruction by the applied anodic potential in alkaline media, and the reconstructed metal hydroxyl oxides are often considered to be the actual active material for oxygen evolution reaction (OER), so how to facilitate surface reconstruction is crucial for their performance. In this paper, the surface reconstruction of NiFe LDH nanosheets was successfully induced by S2- corrosion using rapid wet chemical engineering without affecting their crystal structure and nanomorphology; Notably, the NiOOH species formed on the corroded S-NiFe LDH/NF surface participate in the OER process as active species. The electrochemical measurements show that S-NiFe LDH/NF has a low overpotential of 250 mV and a Tafel slope of 26.3 mV dec -1 at 50 mA cm−2. This work provides a simple activation strategy for the surface reconstruction of NiFe LDH, which is an important reference for the design of advanced catalysts.

Effect of Synthetic Methodology on the Physicochemical Attributes and Electrocatalytic Activity of NiAl-LDHs for the Oxygen Evolution Reaction.

Layered double hydroxides (LDHs) are promising materials for oxygen evolution reactions (OERs), a key component of water splitting to produce hydrogen and oxygen via water electrolysis. However, the performance of LDHs can be limited by their low surface area and poor accessibility of active sites. In this work, we synthesized highly exfoliated 2D NiAl-LDHs by aqueous miscible solvent treatment method (AMOST) and compared its electrocatalytic efficiency with its analogue synthesised via slow urea hydrolysis. We demonstrate that the exfoliated 2D LDHs prepared by AMOST method have a higher surface area and more active sites than the crystalline LDHs obtained through urea hydrolysis, resulting in a superior OER activity and efficiency. The exfoliated 2D LDHs required a lower overpotential of 280 mV to reach a current density of 50 mA cm-2 and it also outperformed IrO2 , a benchmark OER catalyst, in terms of overpotential and stability. We demonstrate that the physicochemical properties of nanosheets derived from NIAl-LDH-based materials are strongly influenced by the synthetic methodology, which affects the exfoliation degree, surface area and active site density. These factors are crucial for improving the OER catalytic performance of these materials, as shown by our results.

Mn doped CoFe layered double hydroxides lead to d-d orbital repulsion toward advanced electrocatalysts for oxygen evolution reaction

Currently, developing highly active and low-cost electrocatalytic materials for oxygen evolution reaction (OER) is an enormously grand challenge. Herein, we developed a novel and highly active Mn doped Co2Fe layer double hydroxide (LDH) electrocatalyst for OER. We discovered that these electrocatalytic materials can be directly grown on carbon papers to construct high-specific-surface-area electrode, which shows the lowest overpotential of 266 mV at 10 mA cm−2. Furthermore, after introducing Mn element, DFT + U calculation found that the ∗OOH of Fe-site on Co2Fe0.67Mn0.33 LDH could draw more electrons than Co2Fe LDH due to the electronegativity differences between Fe-site on Co2Fe0.67Mn0.33 LDH and Fe-site on Co2Fe LDH, which is reason that the energy level of Fe 3d (eg) was obviously downshifted by d-d repulsion of Mn 3d and Fe 3d in the neighboring sites of Co2Fe0.67Mn0.33 LDH after doped Mn element, which leads to reduce charge-transfer energy from O 2p to Fe 3d (eg) to promote oxygen evolution processes for OER. Meanwhile, the band gap is also decreased after doped Mn element in Co2Fe LDH due to the downshifted eg orbital energy of Fe 3d. This study gives a general avenue to design and developing efficiently active LDH electrocatalysts for OER in the future.

Tuning the Structure of Layered Hydroxides for Boosting Energy Application Performance

We are currently on a race against the clock to protect our planet from greenhouse gas emissions. The solution could be inspired from mother nature talking about renewable energies or so-called green energies including wind, solar, hydraulic, biomass and so on, which allows us to reduce the fossil fuels consumption. However, these kinds of energy devices should be coupled to an energy storage system such as batteries and supercapacitors to compensate the absence of wind and sun. For this purpose, we are looking forward to developing strong energy and power application systems by focusing on the development of novel electrode materials.Among 2D materials, layered hydroxides emerge as one of the most attractive electrode materials based on earth-abundant metals, at the same time inside of this family, three type can distinguish: the first one is the Brucite-like structure1 (β-structure) where the metal is arranged in the octahedral position and the interlayer space is defined by Van-Der-Waals interaction. The second one is the Hydrotalcite-like structure also called Layered Double Hydroxide (LDH) recognized by the following formula MII 1-x MIII x (OH)2 Ax. xH2O. The LDH regroups in the same layer a divalent and trivalent metals and are both arranged in the octahedral position2. The Simonkolleite-like structure3 (α-structure) with M1-x Oh Mx Td (OH)2-x Ax. yH2O as formula, is the third type which only contains divalent metals arranged in tetrahedral (Td) and octahedral (Oh) position.Layer double hydroxides are explored materials in the energy field. Multiple studies have been reported on the behaviour of the layered hydroxides materials in energy storage4 and conversion5. This material is very appealing for researchers worldwide due to their good electrochemical behaviour, chemical versatility, electrochemical stability, and their low cost as well6. For instance, LDHs based on earth-abundant elements are good candidates for electrode materials for oxygen evolution reaction (OER) in alkaline condition, as well as for supercapacitors. However, one of the major drawback of these materials is their low electrical conductivity, which represents a limitation in the optimization of the electrochemical performance and the assemble of devices.Among the different approximation to overcome this issue, we are intensively working on the modulation of the electronic properties of LHs. In this line, Co-based α-layered hydroxides, exhibiting simonkolleite-like structure, can be an interesting case of study since the covalent bond between the hydroxylated layer and the anion (figure 1). Indeed, we have recently demonstrated that the electrical properties can be modulated by halide substitution6, where the band gap can be reduced by ligand to metal charge transfer as demonstrated by DFT+U simulations. Considering these previous results, we decided to analyse the role of these chemical modifications in terms of the electrochemical properties.Interestingly, our results evidence a better electrochemical activity of Co-based α-LHs in comparison with the typical β-LHs or LDHs analogues, in both OER and specific capacitance performance7. Moreover, in the case of α-LHs the values can be further enhanced by tuning the nature of the anion: for instance, structures containing iodide overpass in more than 40% those ones containing chloride, as mentioned by DFT+U simulation (figure 2).Hence, this work positions α-CoII hydroxides as key phases among the layered hydroxides family as electrode materials for energy storage and conversion, where the conductivity can be improved by anion substitution8. 1 Brindley, G. W.; Kao, C.-C. Structural and IR Relations among Brucite-like Divalent Metal Hydroxides. Phys. Chem. Miner. 1984, 10 (4), 187–191. 2 Du, Y.; O’Hare, D. Synthesis, Morphology, Structure, and Magnetic Characterization of Layered Cobalt Hydroxyisocyanates. Inorg. Chem. 2008, 47 (8), 3234–3242. 3 Oestreicher, V.; Dolle, C.; Hunt, D.; Fickert, M.; Abellán, G. Room Temperature Synthesis of Two-Dimensional Multilayer Magnets Based on α-CoII Layered Hydroxides. Nano Mater. Sci. 2022, 4 (1), 36–43. 4 Zhang, D.; Cao, J.; Zhang, X.; Zeng, Z.; Insin, N.; Qin, J.; Huang, Y. Modification Strategies of Layered Double Hydroxides for Superior Supercapacitors. Adv. Energy Sustain. Res. 2022, 3 (3), 2100183. 5 Wang, Y.; Yan, D.; El Hankari, S.; Zou, Y.; Wang, S. Recent Progress on Layered Double Hydroxides and Their Derivatives for Electrocatalytic Water Splitting. Adv. Sci. 2018, 5 (8), 1800064. 6 Oestreicher, V.; Hunt, D.; Torres-Cavanillas, R.; Abellán, G.; Scherlis, D. A.; Jobbágy, M. Halide-Mediated Modification of Magnetism and Electronic Structure of α-Co(II) Hydroxides: Synthesis, Characterization, and DFT+U Simulations. Inorg. Chem. 2019, 58 (14), 9414–9424. 7 R. Sanchis-Gual, V. Oestreicher, G. Abellan et al. Submitted. 8 Y. Diouane, V.Oestreicher, G. Abellan et al, manuscript in preparation Figure 1

Activation of ferrocene-based coordination compounds for oxygen evolution and the application in zinc-air battery

Rational reconstruction of oxygen evolution reaction (OER) pre-catalysts and the performance index is crucial but still challenging. Herein, a coordination compound composed by ferrocenedicarboxylic acid and Co2+ was prepared, which was then treated by NaBH4 solution for the rational reconstruction. The electrochemical activation of the treated product results in the generation of oxyhydroxides with unique microstructure acting as the catalytic active phase, which exhibits excellent electrocatalytic activity with a low overpotential of 256 mV for 10 mA cm−2 towards OER and a half-wave potential of 0.69 V (vs RHE) for oxygen reduction (ORR). Ru species was then loaded on the treated product to further improve the catalytic activity for oxygen reduction. The annealed product (Ru-CoFe/C) presents a core-shell structure with carbon layer on the surface. The product presents an increased half-wave potential of 0.744 V (vs RHE) for ORR with the OER/ORR overpotential gap of 0.776 V for 10 and 1 mA cm−2, respectively, showing the bifunctional catalytic activity. Ru species with small size improves the catalytic activity for ORR; the carbon shell provides the high stability. A Zn-air battery was then fabricated with the Ru-CoFe/C catalyst, which delivers a high power density of 88 mW cm−2 and a large specific capacity of 709 mAh g−1, as well as an excellent cycling stability over 65 h, surpassing commercial Pt/C + RuO2 based counterpart, demonstrating its feasibility in the field of renewable electronic devices. This work affords valuable guidelines for the application of ferrocene-based materials in OER and for the exploring of advanced bifunctional ORR/OER catalysts in rational construction of high-quality Zn-air batteries.

Bifunctional vanadium doped mesoporous Co3O4 on nickel foam towards highly efficient overall urea and water splitting in the alkaline electrolyte

Developing more active and stable electrode materials for oxygen evolution reaction (OER) and urea oxidation reaction (UOR) is necessary for electrocatalytic water and urea oxidation which can be used to generate hydrogen. Here, a low-cost vanadium-doped mesoporous cobalt oxide on Ni foam (V/meso-Co/NF) electrodes are obtained via the grouping of an in-situ citric acid (CA)-assisted evaporation-induced self-assembly (EISA) method and electrophoretic deposition process, and work as highly efficient and long-lasting electrocatalytic materials for OER/UOR. In particular, V/meso-Co/NF electrodes require 329 mV overpotential to maintain a 50 mA/cm2, with exceptional long-term durability of 30 h. Interestingly, V/meso-Co/NF also exhibits excellent electrocatalytic UOR performance, reaching 50 and 100 mA/cm2 versus RHE at low potentials of 1.34 and 1.35 V, respectively. By employing the V/meso-Co/NF materials as both the anode and cathode, this urea electrolysis assembly V/meso-Co/NF-5 (+,−) reaches current densities of 100 mA cm−2 at 1.62 V in KOH/urea, which is nearly 340 mV lesser than classical water electrolysis. The V/meso-Co/NF-5 electrocatalysts also exhibit remarkable durability for electrocatalytic OERs and UORs. The obtained findings revealed that the synthesized V/meso-Co/NF might be a promising electrode materials for overall urea-rich wastewater management and H2 generation from wastewater.

NiFe-LDH nanosheets with high activity in three dimensions on NiFe foam electrode for water oxidation

Water decomposition is the most promising system for developing renewable energy, but the sluggish kinetics of the oxygen evolution reaction (OER) is the key limiting factor. Recently, inorganic nanomaterials have been widely used as an effective catalyst for the stimulation of OER kinetics, for which the subsequent dispersion and the current collector are essential. We present a three-dimensional NiFe-layered double hydroxide (NiFe-LDH) synthesized by electrochemical corrosion, with increased electrochemical performance for electrocatalytic water splitting. Electrochemical measurements reveal that the NiFe-LDH has a lower Tafel slope of 46 mVˑdec−1 compared with the NiFe foam. The resulting electrode had a current density of 50 mAˑcm−2 and a remarkably low overpotential of 150 mV. Theoretical calculations and experimental observations showed and explained NiFe-LDH-90 electrode has high alkaline medium endurance, implying excellent OER electrocatalytic activity. The produced composite is expected to bring new insights into the design of foam electrocatalyst materials for OER.