Transition Metal-based Electrocatalysts Research Articles

Construction of micro-nano hierarchical wing-like iron/molybdenum oxide heterojunction with synergistic effect for accelerated overall water splitting

Designing heterojunction catalysts with high-energy interfacial effects, especially combining the geometrical advantages of hierarchical micro-nano structures with the advantages of bi- or multi-metal syergistically optimised electronic coordination environments, is crucial for achieving efficient and stable water splitting. In this study, a simple one-step hydrothermal method was used to construct a hierarchical wing-like iron/molybdenum oxide heterojunction with a porous structure on nickel foam (FMO/NF). The synergistic effect of Fe, Mo, and the heterostructures can enrich structural defects, overcome the disadvantages of the individual components, and improve material performance by optimising the structural configurations and electronic properties and exploiting the electronic interactions that occur between interfaces composed of different phases. In addition, owing to the high porosity of the hierarchical micro-nano structure and abundant active sites, the wing-like FMO/NF was utilised as an efficient bifunctional catalyst for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), presenting low overpotentials of 278.06 and 263.72 mV, respectively, at a current density of 100 mA·cm−2 in 1 mol/L KOH. Furthermore, assembling FMO/NF as both the anode and cathode (FMO/NF || FMO/NF) required a cell voltage of 1.87 V to drive 100 mA·cm−2 in 1 mol/L KOH, and it proceeded continuously for 110 h with negligible cell voltage decay. This work provides a rational synthetic route for the preparation of innovative double transition metal-based micro-nano hierarchical heterostructured electrocatalysts with a synergistic effect and further advances the development of energy-conversion technology.

Interface and cation dual-engineering promoting Ce-Co(OH)2/CoP/NF as bifunctional electrocatalyst toward overall water splitting coupling with oxidation of organic compounds

Transition metal-based electrocatalysts are the promising candidates to substitute noble metal-based catalysts for water electrolysis, owing to its abundant earth reserves and inexpensive fabrication costs. Interface engineering and cation doping engineering are verified as the effective methods to improve the sluggish electrocatalytic performance of transition metal-based electrocatalysts. Here, we synthesized a self-supported heterostructure of Ce doped Co(OH)2 nanosheets/CoP nanowires on the support of nickel foam (Ce-Co(OH)2/CoP/NF) by simple hydrothermal method, low-temperature phosphorization method. The Ce atom doping can lead to lattice distortion and abundant superficial defects on crystal surface, which will generate more active sites and faster charges transformation. The heterointerface between Ce-Co(OH)2 and CoP also can lead to electronic structure modulation at interface domain, which not can induce much fresh active sites in this area, but can optimize the active sites to the optimal state for superior catalytic activity. Benefitting from these, it only needs the overpotentials of 253 and 56 mV to realize 10 mA/cm2 for OER and HER under 1 M KOH solution, which is much enhance than single-phased samples. As the bifunctional electrocatalyst for two-electrode system, it merely requires 1.53 V to attain 10 mA/cm2 in 1 M KOH, and it also exhibits outstanding overall water splitting performance in alkaline natural electrolyte, along with excellent catalytic long-time durability. In addition, the Ce-Co(OH)2/CoP/NF-based electrolyzer also could achieve energy-saving hydrogen production, and simultaneously oxidative degradation of organic materials or biomass upgrading at anode under lower voltages. This work paves a novel idea to fabricate high-efficient bifunctional electrocatalysts for energy-saving H2 production.

Orbital Occupancy and Spin Polarization: From Mechanistic Study to Rational Design of Transition Metal-Based Electrocatalysts toward Energy Applications.

Over the past few decades, development of electrocatalysts for energy applications has extensively transitioned from trial-and-error methodologies to more rational and directed designs at the atomic levels via either nanogeometric optimization or modulating electronic properties of active sites. Regarding the modulation of electronic properties, nonprecious transition metal-based materials have been attracting large interest due to the capability of versatile tuning d-electron configurations expressed through the flexible orbital occupancy and various possible degrees of spin polarization. Herein, recent advances in tailoring electronic properties of the transition-metal atoms for intrinsically enhanced electrocatalytic performances are reviewed. We start with discussions on how orbital occupancy and spin polarization can govern the essential atomic level processes, including the transport of electron charge and spin in bulk, reactive species adsorption on the catalytic surface, and the electron transfer between catalytic centers and adsorbed species as well as reaction mechanisms. Subsequently, different techniques currently adopted in tuning electronic structures are discussed with particular emphasis on theoretical rationale and recent practical achievements. We also highlight the promises of the recently established computational design approaches in developing electrocatalysts for energy applications. Lastly, the discussion is concluded with perspectives on current challenges and future opportunities. We hope this review will present the beauty of the structure-activity relationships in catalysis sciences and contribute to advance the rational development of electrocatalysts for energy conversion applications.

Research Progress of Bifunctional Oxygen Reactive Electrocatalysts for Zinc-Air Batteries.

Zinc-air batteries (ZABs) have several advantages, including high energy density, cheap price and stable performances with good application prospects in the field of power batteries. The charging and discharging reactions for the air cathode of ZABs are the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), respectively, which play an important role in the whole performance of ZAB. Due to the cost and limited reserves of highly active precious metal catalysts, it is crucial to design alternative efficient and stable dual-functional non-precious metal catalysts. In the present review, we present a systematic summary of the recent progress in the use of transition metal-based electrocatalysts as alternatives to precious metals for the positive poles of ZAB air. Combined with state-of-the-art in situ characterization technologies, a deep understanding of the catalytic mechanism of OER/ORR provided unique insights into the precise design of excellent synthetic non-precious metal catalysts from the perspective of atomic structure. This review further shows that the hybrid electric battery is a new strategy to improve the efficiency of the hybrid electric battery, which could be available to alleviate the problem of resource shortage. Finally, the challenges and research trends for the future development of ZABs were clearly proposed.

In Situ Growth of Self-Supporting MOFs-Derived Ni2P on Hierarchical Doped Carbon for Efficient Overall Water Splitting

The in situ growth of metal organic framework (MOF) derivatives on the surface of nickel foam is a novel type of promising self-supporting electrode catalyst. In this paper, this work reports for the first time the strategy of in situ growth of Ni-MOF, where the metal source is purely provided by a nickel foam (NF) substrate without any external metal ions. MOF-derived Ni2P/NPC structure is achieved by the subsequent phosphidation to yield Ni2P on porous N, P-doped carbon (NPC) backbone. Such strategy provides the as-synthesized Ni2P/NPC/NF electrocatalyst an extremely low interfacial steric resistance. Moreover, a unique three-dimensional hierarchical structure is achieved in Ni2P/NPC/NF, providing massive active sites, short ion diffusion path, and high electrical conductivity. Directly applied as the electrode, Ni2P/NPC/NF demonstrates excellent electrocatalytic performance towards both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), with low overpotentials of only 58 mV and 208 mV to drive 10 mA cm−2, respectively, in 1 M KOH. Furthermore, Ni2P/NPC/NF acting as the overall water splitting electrodes can generate a current density of 10 mA cm−2 at an ultralow cell voltage of 1.53 V. This simple strategy paves the way for the construction of self-supporting transition metal-based electrocatalysts.

Ligand-induced electronic structure and morphology regulation in Ni3S2 heterostructures for efficient bifunctional electrocatalysis

Developing highly efficient and robust transition metal-based electrocatalysts for urea and sulfion electrolysis is crucial to the development of sustainable and clean hydrogen energy, however, is still a significant challenge. Herein, we reported a one-step synthetic protocol to fabricate terephthalic acid (TPA) anchored Ni3S2 (TPA-Ni3S2) brush-shaped nanoarrays on nickel foam (NF) skeleton. The introduction of TPA ligands simultaneously regulates the charge transfer and morphology of Ni3S2, thus optimizing the adsorption strength and increasing the number of active sites, thereby improving the catalytic performance. The optimized TPA@Ni3S2/NF exhibits superior electrocatalytic performance toward urea oxidation reaction (UOR) with a low overpotential of 1.0 V at 100 mA cm−2 and excellent operation stability, outperforming the benchmarks and many other previous reported Ni-based catalysts. More excitingly, as for sulfion oxidation reaction (SOR), the TPA@Ni3S2/NF also shows excellent activity, which merely requires 0.48 V to achieve current densities of 100 mA cm−2. Researches of the mechanism by XPS and in-situ Raman spectroscopy revealed abundant active NiOOH derivatives originated from the surface reconstruction of TPA@Ni3S2/NF, which promoted the excellent electrocatalytic performance towards UOR. In-situ DEMS isotope tracing experiments revealed the generation of N2 was derived from urea intermolecular N–N coupling. Ex-UV–vis and in-situ UV–vis spectra further disclosed the reaction mechanism that S2− was oxidized to short-chain polysulfides that were further combined to generate S8. This work provides a feasible strategy and deep understanding to design cost-efficient electrocatalysts for energy-saving hydrogen production and simultaneously eliminating wastewater pollutants.

Facet-tunable coral-like Mo2C catalyst for electrocatalytic hydrogen evolution reaction

Developing efficient and stable transition metal-based electrocatalysts for the hydrogen evolution reaction (HER) in alkaline media remains a great challenge due to slow water dissociation kinetics. Here, a novel coral-like porous nitrogen-doped Mo2C electrocatalyst (3D Mo2C) derived from ZIF-8 doped with phosphomolybdic acid hydrate (POM) was proposed for the electrocatalytic hydrogen evolution reaction via facet regulation. Density functional theory (DFT) calculations clarified that the Mo2C (0 0 2) facet accelerated water dissociation, while the Mo2C (1 0 1) facet more easily adsorbed H* to generate H2. Thus, Mo2C facets (1 0 1) and (0 0 2) with a suitable ratio showed synergistic effects to exhibit excellent alkaline HER performance. The coral-like porous Mo2C exposed sufficient active sites and facilitated electron and mass transfer to accelerate alkaline HER. The 3D Mo2C (1:1) catalyst exhibited excellent HER activity with a low overpotential of 110 mV and a small Tafel slope of 73.9 mV dec−1 in 1 M KOH.

Ni3+-enriched nickel-based electrocatalysts for superior electrocatalytic water oxidation

A good understanding of the strategy to improve the reconstruction process and catalytic mechanism of non-noble transition metal electrocatalysts in the oxygen evolution reaction (OER) is crucial to achieving high-efficiency and energy-saving hydrogen production because it is considered the rate-determining step in water splitting. In this work, Fe-doped NiO nanosheet arrays are prepared on carbon cloth (Fe/NiO/CC) by a simple solution method and subsequent sonication. The Fe dopants facilitate energy-efficient and rapid surface reconstruction, activate more Ni3+ species, and generate more oxygen vacancies to enable fast and efficient OER. As a result, an overpotential of merely 288 mV is required for a current density of 100 mA cm−2 by the Fe/NiO/CC electrocatalyst and a small Tafel slope of 72.6 mV dec−1 is observed in the alkaline electrolyte. Based on density-functional theory calculation, the difference in the bonding and charge redistribution in NiO caused by Fe dopants modulates the electronic structure and coordination unequally, consequently increasing the number of active sites and enhancing the intrinsic catalytic activity as well. The results provide a deeper understanding of how heteroatom doping modulates the intrinsic activity of active atoms in transition metal-based electrocatalysts and reveal the role in reconstruction in electrocatalytic OER.

The design and synthesis of Fe doped flower-like NiS/NiS2 catalyst with enhanced oxygen evolution reaction

• A cheap Fe doped flower-like NiS/NiS 2 catalyst for OER is designed and synthesized. • Fe doping regulates the phase composition, heterogeneous interface and OER activity. • Fe-NiS/NiS 2 catalyst demonstrates excellent OER performance, exceeding RuO 2 and NiS 2 . Exploring low-cost and high-activity transition metal-based electrocatalysts for oxygen evolution reaction (OER) is critical toward mass hydrogen generation by water splitting. Herein, a cheap Fe element doped flower-like nickel sulfides catalyst (Fe-NiS/NiS 2 ) is designed and synthesized through facile electrostatic adsorption and sulfuration methods. It is investigated that the Fe doping effectively induces the lattice contraction of nickel sulfides and regulates the phase composition and heterogeneous interfaces, thus enabling high intrinsic OER activity. The Fe-NiS/NiS 2 catalyst shows a high electrochemically active surface area of 150 cm 2 , a small overpotential of 361 mV at 100 mA cm −2 and a low Tafel slope of 61.5 mV dec -1 . Furthermore, the Fe-NiS/NiS 2 exhibits a very excellent structure and performance stability without current attenuation for 24 h at 1.50 V versus reversible hydrogen electrode. This work provides an important insight for the exploitation of low-cost and high-performance OER catalysts with cheap Fe element doping metal sulfides.

Optimizing the electronic structure of CoNx via coupling with N-doped carbon for efficient electrochemical hydrogen evolution

Transition metal nitrides (TMNs) have been regarded as an excellent class of electrocatalysts for hydrogen evolution reaction (HER), but there is still huge room for improvement. In this work, cobalt nitride (CoNx) coupled with N-doped carbon (NC) and supported by nickel foam (NF) is designed as an efficient HER electrocatalyst (NF/CoNx@NC). The introduction of NC can not only optimize the electronic structure of CoNx to boost the intrinsic activity, but also enhance the electronic conductivity and stability of the catalyst. As a result, NF/CoNx@NC exhibits excellent HER performance. On the one hand, it only needs an overpotential of 69 mV to deliver a current density of 20 mA cm−2 in 1.0 mol/L KOH, far better than that of CoNx (182 mV). On the other hand, the electronic conductivity and stability of the catalyst can be significantly enhanced after the introduction of NC. This work has done successful material design with the goal of enhancing the intrinsic activity, electronic conductivity, and stability, which has certain reference and guiding significance for the design of novel transition metal-based electrocatalysts.

Routes to enhanced performance of electrolytic hydrogen evolution reaction over the carbon-encapsulated transition metal alloys

A substantial and steady decrease in the energy cost produced from renewable sources has revived interest in hydrogen production through water electrolysis. Deployment of electrolysis for H2 production is now closer to reality than ever before. Yet, several challenges associated with production cost, infrastructure, safety, storage, and so forth remain to be addressed. One of the overriding challenges is the production cost caused by a platinum electrode. To overcome such limitations, developing low-cost and stable electro­catalysts very close to the same electrode activity as platinum (Pt) metal is crucial to solving the efficiency issue in the process. Therefore, this review is in the direction of designing binary and ternary alloys of transition metal-based electrocatalysts anchored on carbon and focuses more on routes to enhance the performance of the hydrogen evolution reaction (HER). The strategic routes to reduce overpotential and enhance electrocatalysts perfor­mance are discussed thoroughly in the light of HER mechanism and its derived descriptor.

Coupling boron-modulated bimetallic oxyhydroxide with photosensitive polymer enable highly-active and ultra-stable seawater splitting

Seawater photoelectrolysis is showing huge potential in green energy conversion field, yet it is still a formidable challenge to develop one catalyst that can drive the electrolysis reaction stably, economically and efficiently. Motivated by this point, the inorganic–organic hybridization strategy is proposed to in-situ construct one hierarchical electrode via concurrent electroless plating and polymerization, which assures the growth of boron-modulated nickel–cobalt oxyhydroxide nanoballs and photosensitive polyaniline nanochains on the self-supporting Ti-based foil (B-CoNiOOH/PANI@TiO2/Ti). Upon inducing photoelectric effect (PEE), the designed target electrode delivers overpotentials as low as 196 and 398 mV at 100 mA cm−2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, corresponding to an activity enhancement by about 15% as compared to those without PEE. Inspiringly, when served as bifunctional electrocatalysts for overall seawater electrolysis, it can stably maintain at 200 mA cm−2 with negligible decay over 72 h. Further analysis reveals that the exceptional catalytic performance can be credit to the B-CoNiOOH, polyaniline (PANI) and TiO2 subunit coupling-induced physically and chemically synergistic catalysis effect such as admirable composition stability, photoelectric function and adhesion capability. The finding in this contribution may trigger much more broad interest to the novel hybrid catalysts consisting of photosensitive polymer and transition metal-based electrocatalysts.

Template-directed shape control synthesis of rare earth sulfide for oxygen evolution reaction

Electrochemical water splitting for the generation of hydrogen and oxygen has great importance for energy storage and conversion technologies. The availability of an efficient electrocatalysts for oxygen evolution reactions to produce molecular oxygen is very important for development renewable energy technologies. The design and successfully development of an efficient electrocatalyst with controlled surface morphologies are still great challenge towards oxygen evolution reaction (OER). Till now various transition metal-based electrocatalysts have been developed with remarkable catalytic activity. In present study we have developed rare earth sulfides La2S3 and Sm2S3 using template assisted hydrothermal method and applied as catalyst for OER. The developed catalysts have been characterized by different techniques such as X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), high-resolution transmission electron microscope (HRTEM), furrier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption isotherm (BET) and energy dispersive spectroscopy (EDS) with qualitative and quantitative estimation. The developed catalysts La2S3 and Sm2S3 offered overpotential 239 and 343 mV vs. RHE, respectively, to attain current density 10 mA cm−2. The efficient tube shaped catalyst La2S3 is better than Sm2S3 and exhibited faster kinetics with small Tafel slope 59.32 mV decade−1.

(Digital Presentation) Nickel-Iron Electrocatalysts Modified with Group 11 Metals Achieving 1 A cm−2 of Oxygen Evolution in Buffered Near-Neutral pH Electrolyte

Electrocatalytic processes driven by the renewable electricity will play a pivotal role to achieve sustainable in our society, whereby the thermodynamically stable chemicals are converted into value-added products or energy carriers. For instance, the water electrolysis produces green hydrogen, and the carbon dioxide electrolysis yields commodity chemicals such as ethylene or carbon monoxide.[1] These processes commonly share an anodic half-reaction of oxygen evolution reaction (OER) that requires large overpotentials due to its slow kinetics, leading to the significant loss of overall energy efficiency.[2] This is particularly the case at near-neutral pH,[3] which however is likely the desired condition for electrocatalytic CO2 reduction due to the lessened loss of carbon dioxide via carbonate formation that prevails in alkaline conditions.[4] Toward the large-scale operation of these technologies, it is highly desired to develop an active, stable, and earth-abundant metal based electrocatalyst that catalyzes the OER at near-neutral pH and high current densities.The present study reports on our discovery of the transition metal-based electrocatalysts that efficiently catalyze OER in carbonate buffer electrolyte at near-neutral pH. Firstly, a variety of electrodes were fabricated by electro-deposition of transition metals (manganese, iron, cobalt, copper) on electrochemically activated Ni (ECA-Ni) substrates[5] with nanostructured surface. Their electrocatalytic testing revealed that iron oxide (Fe-O) modified ECA-Ni achieved a current density of 100 mA cm−2 at an overpotential of ca. 280 mV in dense electrolyte of 1.5 mol kg−1 K-carbonate solution and 353 K, whose pH was adjusted to pH 10.5 at 298 K prior to the testing. This pH level was essential to achieve stable operation using the Ni-Fe electrode. Subsequently, group 11 metals of copper, silver, or gold were introduced into Fe-O/ECA-Ni via co-electrodeposition to tailor the nature of active site for improved OER. Remarkably, electrodes of Fe-Cu-O/ECA-Ni and Fe-Au-O/ECA-Ni catalyzed the OER at a rate of 1 A cm−2 and an overpotential of ca. 330 mV, whose figure is comparable to those in extremely alkaline conditions (Figure 1). Long-term and on-off stability testing revealed that the developed electrodes maintained its performance. Our characterization on double-layer capacitance indicated the enlarged surface area of Fe-Cu-O and Fe-Au-O electrodes with respect to the pristine Fe-O counterparts, which partly contributed to the improved OER performance. In addition, ex situ X-ray photoelectron spectroscopy and in situ X-ray absorption spectroscopy concurrently pointed to the presence of stable Fe(III) species for Fe-Cu-O/ECA-Ni, plausibly FeOOH. The present study discovered transition metal based electrocatalysts for the OER at near-neutral pH and high current densities, achieving comparable performance to those in alkaline conditions, which is significant given the merits of near-neutral pH condition for CO2 reduction. These findings represent the potentiality of near-neutral pH electrochemical system on industrial scale, which can help to construct a sustainable society.Reference[1] S. Chu, A. Majumdar, Nature 2012, 488, 294.[2] T. Reier, H. N. Nong, D. Teschner, R. Schlögl, P. Strasser, Adv. Energy Mater. 2017, 7, 1601275.[3] T. Nishimoto, T. Shinagawa, T. Naito, K. Takanabe, ChemSusChem 2021, 14, 1554.[4] J. A. Rabinowitz, M. W. Kanan, Nat. Commun. 2020, 11, 5231.[5] T. Shinagawa, M. T.-K. Ng, K. Takanabe, Angew. Chem. Int. Ed. 2017, 56, 5061. Figure 1

(Invited) Regulating Electronic Structure for Clean Energy Powered Water Electrolysis on Non-Precious Catalysts

The need for clean energy, predominantly wind and sun, to replace fossil fuels is in high demand for the carbon neutrality. The intermittent nature of the renewable energy sources is one of the most important challenges. A potential solution is to store the extra electricity in the form of chemical fuels, and then reconvert on demand. Electrochemical water splitting to produce hydrogen and oxygen is an appealing and sustainable approach. The benchmark electrocatalysts for water electrolysis are noble metal Pt- and Ir/Ru-based materials. Nevertheless, the scarcity and the high cost of these precious catalysts severely hinder their widespread applications. Developing non-precious electrocatalysts has been one long-term target, but still remains a great challenge. In this presentation we will show our research efforts and design strategies by regulating the electronic structures on transition metal-based electrocatalysts for hydrogen evolution, oxygen evolution as well as constructing the water electrolyzer powered by solar energy.

Bimetallic polyoxometalate derived Co/WN composite as electrocatalyst for high-efficiency hydrogen evolution

Electrocatalytic hydrogen evolution reaction (HER) is a simple way to generate environment-friendly hydrogen energy. Due to the high price and low content, the wide application of noble metal-based electrocatalysts is limited. It is of great significance to study inexpensive, high-performance non-precious metal-based electrocatalysts. In this work, bimetallic nitride (Co/WN@NC) was successfully prepared through a one-step high-temperature calcination way using dicyandiamide (DCA), bimetallic polyoxometalates, and cobalt nitrate. Co/WN@NC exhibits outstanding catalytic performance with the same overpotentials of 143 mV in both alkaline and acidic media at 10 mA cm−2. The Tafel slopes are 90 mV dec−1 and 118 mV dec−1, respectively. Co/WN@NC exhibits good stability in acidic and alkaline solutions for up to 30 h. The splendid catalytic performance can be mainly ascribed to the synergistic effect between Co and WN. This work shows experimental guiding significance for preparing simple transition metal-based electrocatalysts.

Oxygen-vacancy-rich CoFe/CoFe2O4 embedded in N-doped hollow carbon spheres as a highly efficient bifunctional electrocatalyst for Zn–air batteries

Exploring transition metal-based bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is essential for implementing rechargeable Zn–air batteries (ZABs). Herein, we synthesized oxygen-vacancy-rich CoFe/CoFe2O4 embedded in N-doped hollow carbon spheres (Vo-CoFe/CoFe2O4@NC) through pyrolysis, carbonization, and partial reduction. The synergistic effect of introducing oxygen vacancies into CoFe2O4 and the well-defined heterointerfaces between the CoFe alloy and spinel-type CoFe2O4 moderately controlled the electronic structure and provided abundant active sites for the ORR and OER. Vo-CoFe/CoFe2O4@NC exhibited high ORR activity (half-wave potential: 0.858 V and Tafel slope: 56 mV dec–1) and delivered a low overpotential (360 mV at 10 mA cm−2) for the OER. Moreover, rechargeable ZABs using Vo-CoFe/CoFe2O4@NC as the air cathode revealed excellent open-circuit voltage (1.53 V), good power density (139.5 mW cm−2), and longer cycling durability than the state-of-the-art Pt/C-RuO2.

Anodic corrosion of heteroatom doped graphene oxide supports and its influence on the electrocatalytic oxygen evolution reaction

Transition metal-based electrocatalysts supported on carbon substrates face the challenges of anodic corrosion of carbon during oxygen evolution reaction at high oxidation potential. The role of electrophilic functional groups (carbonyl, pyridinic, thiol, etc.) incorporated in graphene oxide has been studied towards the anodic corrosion resistance. Heteroatom functionalized carbon supports possess modified electronic properties, surface oxygen content, and hydrophilicity, which are crucial in governing electrochemical corrosion in the alkaline oxidative environment. Evidently, electron-withdrawing groups in NGO support (pyridinic, cyano, nitro, etc) and its lower oxygen content impart maximum corrosion resistance and anodic stability in comparison to the other sulfur-doped and co-doped graphene oxide support. In this report, we establish the baseline evaluation of carbon-supported OER electrocatalysts by a systematic analysis of activity and substrate corrosion resistance. The result of this study establishes the role of surface composition of the doped supports while for designing a stable, corrosion-resistant OER electrocatalyst.

Co-Based Nanosheets with Transitional Metal Doping for Oxygen Evolution Reaction.

Activated two-dimension (2D) materials are used in various applications as high-performance catalysts. Breaking the long-range order of the basal plane of 2D materials can highly promote catalytic activity by supplying more active sites. Here we developed a method to synthesize ultrathin MCoOx (M = V, Mn, Fe, Ni, Cu, Zn) amorphous nanosheets (ANSs). These Co-based ANSs show high oxygen evolution reaction (OER) activity in alkaline solution due to the broken long-range order and the presence of abundant low bonded O on the basal plane. The stable Fe1Co1Ox ANSs also show an overpotential of ca. 240 mV of achieving 10 mA/cm2 in OER, better than most reported transition metal-based electrocatalysts.

Intermolecular Energy Gap-Induced Formation of High-Valent Cobalt Species in CoOOH Surface Layer on Cobalt Sulfides for Efficient Water Oxidation.

Transition metal-based electrocatalysts will undergo surface reconstruction to form active oxyhydroxide-based hybrids, which are regarded as the "true-catalysts" for the oxygen evolution reaction (OER). Much effort has been devoted to understanding the surface reconstruction, but little on identifying the origin of the enhanced performance derived from the substrate effect. Herein, we report the electrochemical synthesis of amorphous CoOOH layers on the surface of various cobalt sulfides (CoSα ), and identify that the reduced intermolecular energy gap (Δinter ) between the valence band maximum (VBM) of CoOOH and the conduction band minimum (CBM) of CoSα can accelerate the formation of OER-active high-valent Co4+ species. The combination of electrochemical and in situ spectroscopic approaches, including cyclic voltammetry (CV), operando electron paramagnetic resonance (EPR) and Raman, reveals that Co species in the CoOOH/Co9 S8 are more readily oxidized to CoO2 /Co9 S8 than in CoOOH and other CoOOH/CoSα . This work provides a new design principle for transition metal-based OER electrocatalysts.