Oxygen Evolution Reaction Catalytic Activity Research Articles

Enhanced Electrocatalytic Activity of Amorphized LaCoO3 for Oxygen Evolution Reaction.

Amorphous inorganic perovskites have attracted significant attention as efficient electrocatalysts due to their unique structural flexibility and good catalytic activity. In particular, the disordered structure and a surface rich in defects such as oxygen vacancies can contribute to the superior electrocatalytic activity of amorphous oxides compared to their crystalline counterpart. In this work, we report the synthesis of LaCoO3, followed by an amorphization process through urea reduction with tailored modifications. The as-synthesized catalysts were thoroughly tested for their performance in oxygen evolution reaction (OER), Remarkably, the amorphous LaCoO3 synthesized at 450 °C (referred to as LCO-4) exhibits excellent OER catalytic activity. At an overpotential of 310 mV, it achieved a current density of 10 mA/cm-2, exceedingly fast to 1 A/cm-2 at an overpotential of only 460 mV. Moreover, LCO-4 exhibited several advantageous features compared to pristine LaCoO3 and LaCoO3 amorphized at other two temperatures (350 °C, LCO-3, and 550 °C, LCO-5). The amorphized LCO-4 catalyst showed a higher electrochemically active surface area, a key factor in boosting catalytic performance. Additionally, LCO-4 demonstrated the lowest Tafel slope of 70 mVdec-1, further highlighting its exceptional OER activity. Furthermore, the long-term stability of LCO-4 is notably superior than pristine LaCoO3 (LCO-P) and the other amorphized samples (LCO-3 and LCO-5). The enhanced catalytic activity of LCO-4 can be attributed to its unique disordered structure, small crystallite size, and higher concentration of oxygen vacancies in the final catalyst.

Substrate-Driven Electrocatalysis of Natural and Earth-Abundant Pyrite Towards Oxygen Evolution Reaction

The fabrication of an economical, earth-abundant, environment-friendly, and highly efficient electrocatalyst for anodic oxygen evolution reaction (OER) in the electrolysis of water is essential for sustainable energy conversion and storage technology. Among the various transition metal-based electrocatalysts, iron-based electrocatalysts are well-known for their catalytic behavior due to their effective redox activity, abundance, and low toxicity. Pyrites are the most prevalent Fe-containing minerals in the earth's crust, but their use as an electrocatalyst for oxygen evolution reaction (OER) has received little attention though their synthetic counterparts have shown better activity. Herein, the naturally occurring pyrite (FeS2) on Ni foam is evaluated as a dynamic electrocatalyst towards OER in alkaline media. Various spectro-analytical techniques have been used to confirm the chemical and physical characteristics of earth abundant pyrite. The pyrite-coated nickel foam exhibited an extraordinarily superior catalytic activity for OER with overpotential of 203 and 315 mV at current densities of 10 mA∙cm−2 and 50 mA∙cm−2, respectively in 1.0 M potassium hydroxide (KOH) electrolyte at a scan rate of 5 mV∙s−1. Meanwhile, the benchmark precious iridium oxide (IrO2) on nickel foam demonstrated an overpotential of 322 and 430 mV for OER at 10 and 50 mA∙cm−2, respectively. It's important to note that the catalyst used is a natural pyrite with some additional constituents in small quantities. Therefore, the analysis revealed the presence of carbon (C), silicon (Si) and oxygen (O) in addition to FeS2. This composition, along with the synergistic behavior of nickel ions from the nickel foam, likely contributes to the enhancement in catalytic activity observed. The pyrite on carbon substrate, did not exhibit the same impressive OER activity as like on Ni foam, emphasizing the significance of the substrate-dependent performance. Nevertheless, on the nickel foam, natural pyrite displayed the lowest overpotential, Tafel slope, and better stability for OER. Hence, on Ni foam substrate, earth-abundant, low-cost, stable, and efficient pyrite-based catalyst augmented by synergistic interactions with nickel ions, may hold great promise for advancing the field of water electrolysis and facilitating cleaner energy production and conversion.

Photo-driven electrochemical etching to construct porous structures with oxygen vacancies on ZnO photoanodes for efficient solar water splitting

Fast charge separation and oxidation kinetics are the key issues for photoelectrochemical (PEC) water splitting. Herein, photo-driven electrochemical etching (PEE) was applied to modify the morphology and surface properties of ZnO photoanodes to improve PEC performance. By regulating the applied potential and treatment time, the PEE generated a lotus root like porous structure with a pore diameter of 20–30 nm and depth of about 300 nm, and produced a large amount (30.1 %) of oxygen vacancies (Ov) on ZnO photoanode. PEE treated-ZnO array demonstrated a charge separation efficiency of 87 %, and achieved 1.8 times larger photocurrent (1.26 mAcm−2 at 1.23 VRHE) with a cathodic shift of onset potential of 0.12 VRHE than pristine ZnO. The introduced Ov and the shortened charge transport distance of porous microstructures by PEE treatment improved the electrode/electrolyte interface charge transfer and water oxidation kinetics. DFT calculations indicate that the construction of oxygen defects on the catalyst surface can reduce the overpotential of oxygen evolution reaction (OER) and further promote the catalytic activity of OER. Moreover, electrode surface pore structure can be tailored by adjusting illumination parameters and electrolytes. This work illustrates a novel and effective approach to tunable photo-corrodible electrode materials for solar water splitting.

Structural Engineering of Co-Metal-Organic Frameworks via Ce Incorporation for Improved Oxygen Evolution.

The rational design of metal-organic framework (MOF)-basedelectrocatalysts plays a key role in achieving high-efficiency oxygen evolution reaction (OER). Herein, a synergetic morphology and electronic structure engineering strategy are proposed to design a Co-MOF nanoflower grown on carbon paper via rare-earth cerium doping (CoCe-MOF/CP). Compared with Co-MOF/CP, the developed CoCe-MOF/CP exhibited superior OER performance with a low overpotential of 267mV at 10mA cm-2 and outstanding long-term stability over 100h. Theoretical calculations show that the unique 4f valence electron structure of Ce induced charge redistribution of the Co-MOF surface through the strong Co 3d-O 2p-Ce 4f orbital electronic coupling below the Fermi level. Ce-doped plays a key role in the engineering of the electronic states of the Co sites to endow them with the optimal free energy landscape for enhanced OER catalytic activity. This work provides new insights into comprehending the RE-enhanced mechanism of electrocatalysis and provides an effective strategy for the design of MOF-based electrocatalysts.

Amorphous high-entropy IrRuCrFeCoNiOx as efficient water splitting oxygen evolution reaction electrocatalysts

The process of oxygen evolution reaction (OER) for water splitting is intricate and demands a substantial amount of energy. It necessitates the utilization of catalysts that are both highly efficient and durable in order to overcome the slow reaction kinetics. Amorphous, high-entropy oxide nanoparticles were prepared using simple one-step coprecipitation in this work. Due to highly disordered atomic arrangement in the amorphous structure of these catalysts and their high specific surface area, they compete to form active sites in the OER. Among them, IrRuCrFeCoNiOx demonstrated the optimal OER catalytic activity, requiring just a low overpotential (190 mV) with minimal Tafel slope (51.1 mV dec−1) to achieve the current density of 10 mA cm−2 in 1 M KOH. Through surface self-reconstruction in the OER, a crystalline active layer with a thickness of several nanometers formed on the catalyst’s surface. The stable core-shell nanoarchitectures composed of crystalline and amorphous regions substantially improved the stability of the catalyst. This work verified the effectiveness of high-entropy design and the significant improvement of noble metal doping on OER performance. It develops a new OER catalyst for water splitting with great activity and stability.

NiCo-LDH Hollow Nanocage Oxygen Evolution Reaction Promotes Luminol Electrochemiluminescence.

Conventional luminol co-reactant electrochemiluminescence (ECL) systems suffer from low stability and accuracy due to factors such as the ease of decomposition of hydrogen peroxide and inefficient generation of reactive oxygen species (ROS) from dissolved oxygen. Inspired by the luminol ECL mechanism mediated by oxygen evolution reaction (OER), the nickel-cobalt layered double hydroxide (NiCo-LDH) hollow nanocages with hollow structure and defect state are used as co-reaction promoters to enhance the ECL emission from the luminol-H2 O system. Thanks to the hollow structure and defect state, NiCo-LDH hollow nanocages show excellent OER catalytic activity, which can stabilize and efficiently produce ROS and enhance the ECL emission. Additionally, mechanistic exploration suggests that the ROS involved in the co-reaction of the luminol-H2 O system are derived from the OER reaction process, and there is a positive correlation between ECL intensity and the OER catalytic activity of the co-reaction promoter. The selection of catalysts with excellent OER catalytic activity is a key factor in improving ECL emission. Finally, a dual-mode immunosensor is constructed for the detection and analysis of alpha-fetoprotein (AFP) based on the promoting effect of NiCo-LDH hollow nanocages on the luminol-H2 O ECL system.

Achieving High Activity and Long-Term Stability towards Oxygen Evolution in Acid by Phase Coupling between CeO2-Ir.

The development of efficient and stable catalysts with high mass activity is crucial for acidic oxygen evolution reaction (OER). In this study, CeO2-Ir heterojunctions supported on carbon nanotubes (CeO2-Ir/CNTs) are synthesized using a solvothermal method based on the heterostructure strategy. CeO2-Ir/CNTs demonstrate remarkable effectiveness as catalysts for acidic OER, achieving 10.0 mA cm-2 at a low overpotential of only 262.9 mV and maintaining stability over 60.0 h. Notably, despite using an Ir dosage 15.3 times lower than that of c-IrO2, CeO2-Ir/CNTs exhibit a very high mass activity (2542.3 A gIr-1@1.53 V), which is 58.8 times higher than that of c-IrO2. When applied to acidic water electrolyzes, CeO2-Ir/CNTs display a prosperous potential for application as anodic catalysts. X-ray photoelectron spectrometer (XPS) analysis reveals that the chemical environment of Ir nanoparticles (NP) can be effectively modulated through coupling with CeO2. This modulation is believed to be the key factor contributing to the excellent OER catalytic activity and stability observed in CeO2-Ir/CNTs.

Regulation of Co3O4 morphology via ionic liquid for efficient bifunctional electrocatalysts

In the context of energy scarcity, the development of bifunctional electrocatalysts with both high efficiency and activity is crucial. Extensive research has focused on Co3O4, showing significant promise as a catalyst for both the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). However, the impact of Co3O4 morphology on catalytic activity remains unclear. Herein, Co3O4 of different morphology was synthesized by tuning ionic liquid (C10H15N5) content during a one step solvothermal and subsequent low temperature heat treatment approach. In this process, the competitive coordination of C10H15N5 with different content and cobalt nitrate enables the regulation of the morphology of cobalt carbon composite (Referred to as amCoC). After pyrolysis, the obtained Co3O4 not only inherited the morphology of the amCoC, but also exposed different active sites. In particular, compared with other morphologies of Co3O4, the open yolk-shell Co3O4 exposed more active sites and exhibited special morphology, and had stronger catalytic activity of OER and ORR. This strategy paves the way for optimizing the morphology of Co3O4 catalysts to improve catalytic activity.

Interfacial engineering design for one-dimensional cobalt-iron selenide nanomaterials as a high-efficiency catalyst for oxygen evolution reaction

One promising approach to improving the slow reaction dynamics of alkaline oxygen evolution reaction (OER) is to construct non-precious metal-based heterojunctions via interface engineering. In this work, the relationship between structure and activity for one-dimensional CoSe2/FeSe2 nanomaterials for OER is discussed in detail by experimental techniques, coupled with the density functional theory calculations. Capitalizing on the refined electronic structure layout and abundant heterogeneous interfaces, the hierarchical branched CoSe2/FeSe2 heterojunctions demonstrate the outstanding electrocatalytic activity for OER in 1 M KOH solution, and can achieve low overpotentials of 283 and 330 mV at current densities of 10 and 100 mA cm−2, respectively, as well as keeping 94.7 % of its initial activity after 100 h cycles.Furthermore, it is found that the enhanced inherent catalytic performance of CoSe2/FeSe2 electrocatalyst after standardizing the current density with electrochemically active surface area (ECSA) could be attributed to the robust interaction at the interface induced by the construction of the heterojunctions. This work presents the significance of manipulating the electronic structure of electrocatalysts utilizing interface design to enhance OER catalytic activity, and provides new insights for exploring the highly active electrocatalysts.

Nanostructured Pt@RuOx catalyst for boosting overall acidic seawater splitting

In the domain of acidic water splitting, designing bifunctional catalysts that marry high activity with enduring stability is a formidable challenge. Herein, we have constructed platinum-containing ruthenium oxide nanoparticles (Pt@RuOx NPs) to achieve excellent overall water splitting performance in acidic electrolytes. Pt@RuOx NPs demonstrate exceptional catalytic activity for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in acidic seawater, requiring overpotentials of only 20 and 157 mV, respectively to achieve a current density of 10 mA cm−2. Furthermore, in 0.5 M H2SO4, this catalyst exhibits high HER (19 mV) and OER (236 mV) catalytic activities. The two-electrode water splitting system composed of bifunctional Pt@RuOx NPs requires cell voltages of only 1.442 and 1.465 V to deliver a current density of 10 mA cm−2 in acidic seawater and 0.5 M H2SO4. Remarkably, this catalyst displays remarkable stability in the water splitting process. It is shown that the introduction of Pt could augment oxygen vacancies and enhance catalytic activity significantly. The synergy between Pt and Ru further contributes to the improved performance. Additionally, we have observed that acidic seawater holds distinct advantages for acidic water splitting, along with a thorough exploration of the relationship between Cl− concentration and catalytic performance. This study not only provides a strategy to improve the catalytic activity and stability of ruthenium-based catalysts for water splitting in acidic environments, but also unveils the promoting effect of Cl− on the catalytic activity in acidic water splitting.

Two Birds with One Stone: Contemporaneously Enhancing OER Catalytic Activity and Stability for Dual-Phase Medium-Entropy Metal Sulfides.

Transition metal-based sulfides exhibit remarkable potential as electrocatalysts for oxygen evolution reaction (OER) due to the unique intrinsic structure and physicochemical characteristics. Nevertheless, currently available sulfide catalysts based on transition metals face a bottleneck in large-scale commercial applications owing to their unsatisfactory stability. Here, the first fabrication of (FeCoNiMn2 )S2 dual-phase medium-entropy metal sulfide (dp-MEMS) is successfully achieved, which demonstrated the expected optimization of stability in the OER process. Benefiting from the "cell wall" -like structure and the synergistic effect in medium-entropy systems, (FeCoNiMn2 )S2 dp-MEMS delivers an exceptionally low overpotential of 169 and 232mV at current densities of 10 and 100mAcm-2 , respectively. The enhancement mechanism of catalytic activity and stability is further validated by density functional theory (DFT) calculations. Additionally, the rechargeable Zn-air batteries integrated with FeCoNiMn2 )S2 dp-MEMS exhibit remarkable performance outperforming the commercial catalyst (Pt/C+RuO2 ). This work demonstrates that the dual-phase medium-entropy metal sulfide-based catalysts have the potential to provide a greater application value for OER and related energy conversion systems.

Bifunctional catalysts of modified doped small-sized ZIF and CNTs with entangled structures

For optimizing the lifetime and power of Zn-Air batteries (ZABs), we develop Fe, Co bimetallic doped zeolite imidazolate framework (M@CoFe-ZIF-8) from the perspective of catalytic reaction. After the pyrolysis treatment, the catalyst shows an entangled structure of 100 nm-sized ZIF-8 particles and carbon nanotubes (CNTs). The experimental result shows that the 100 nm-sized CoFe@MNC-CNTs (MNC: metal and nitrogen doped carbon) have better ORR (oxygen reduction reaction) and OER (oxygen evolution reaction) catalytic activities compared with the 1 μm-sized CoFe@BMNC-CNTs structures with the assistance of melamine. On the one hand, it is closely related to the larger specific surface area and mesoporous structure of CoFe@MNC-CNTs. On the other hand, uniformly distributed metal nitrogen (M-Nx) sites and carbon nanotube-wrapped metal nanoparticles may both be effective catalytic active sites for ORR and OER. The CoFe@MNC-CNTs exhibits remarkable catalytic performance, outperforming the commercially available 20 % Pt/C catalyst with a higher half-wave potential (0.865 V vs 0.838 V) in alkaline electrolyte. Meanwhile, the overpotential (Eover) also rivals that of the commercially available RuO2 catalyst. The Zn-air batterry based on CoFe@MNC-CNTs exhibits excellent power density, which is significantly better than Pt/C catalyst (112.1 mW·cm−2 vs 98.2 mW·cm−2). The CoFe@MNC-CNTs also exhibits over 65 h of cycling stability (10 mA·cm−2). In addition, the open circuit voltage (OCV) and cycle time of the flexible battery based on the catalyst of CoFe@MNC-CNTs remain satisfactory (1.525 V, 18 h).

Advance of manganese dioxide-based electrocatalyst for water splitting

Manganese dioxides have been recognized as one of the most attractive candidates for water splitting due to their unique properties of low cost, environmental friendliness, multiple morphologies and polymorphs. However, further applications of MnO2-based materials have been limited since their oxygen evolution reaction (OER) efficiency is still not quite ideal. This, this review summarizes recent research advances in manganese dioxide-based composites for oxygen evolution reactions. The morphological control, structure construction, defect engineering, atom doping, and binary/ternary heterojunctions have been performed to enhance their OER catalytic activity. Finally, the gaps in the research of MnO2-based materials in the field of OER catalysis are presented and the challenges and development directions for future research are outlined. Therefore, this may provide a guideline for the rational design and construction of efficient MnO2-based catalytic OER in the future.

Core–shell heterostructure engineering of CoP nanowires coupled NiFe LDH nanosheets for highly efficient water/seawater oxidation

Searching for efficient nonprecious metal-based catalysts toward oxygen evolution reaction (OER) are of significance for seawater electrolysis. Herein, a core–shell-structured hybrid of cobalt phosphide nanowires@NiFe layered double hydroxide nanosheets grown on conductive nickel foam (CoP@NiFe LDH/NF) is prepared by a feasible approach at low temperature. The charming structure can provide numerous phosphide/hydroxide heterogenous interfaces, expose abundant active sites, and boost electron/mass transfer, synergistically enhancing catalytic OER activity. When employed as an electrocatalyst toward the OER, the resultant CoP@NiFe LDH/NF only requires a small overpotential of 287 mV to provide 300 mA/cm2 current density as well as long-time durability in 1.0 mol/L KOH seawater. The regulation of electronic states and surface reconstruction synergistically contribute to highly efficient seawater oxidation. This work provides an opportunity to construct efficient and inexpensive electrocatalysts for hydrogen production.

Efficiency of nanostructured CuxCo3-xO4 and NixCu1-xCo2O4 electrodes as electrocatalysts for the oxygen evolution reaction–revisited

Binary and ternary cobalt-based spinel oxides have been shown to possess enhanced electrocatalytic activity and stability towards the oxygen evolution reaction (OER), however their performance is inconsistent. In this work, copper and nickel-copper substituted cobalt spinel oxides, CuxCo3-xO4 (x = 0, 0.25, 0.5, 0.75 and 1) and NixCu1-xCo2O4 (x = 0.25, 0.5, 0.75, 0.9 and 1), were prepared by the thermal decomposition method to re-examine their properties. We used several physical and chemical characterization methods to understand their behavior. The formation of spinel structure was confirmed by X-ray diffraction analysis, however, CuxCo3-xO4 remains monophasic only up to x = 0.75. CuCo2O4 was found to contain an additional CuO phase. The lattice parameters were determined as a function of the composition and found to increase with increased Cu and Ni content in the cobalt spinel lattice, which supports Cu and Ni incorporation in the spinel structure. For CuxCo3-xO4 electrodes, the lattice parameter gradually increased when cobalt is replaced by copper in the composition. NixCu1-xCo2O4 lattice parameters are higher than those of CuxCo3-xO4 but do not display a particular trend with replacement of Cu by Ni. The XPS analysis indicates the existence of various chemical species on the surface of the electrodes with a significant amount of NiO being detected on the surface of Ni-containing samples. The core-level spectra of all metal cations indicate the presence of mixed-valence states in the spinel structure. The roughness factor was determined by measuring the double layer capacitance of the electrodes using cyclic voltammetry and the data obtained was verified by performing electrochemical impedance spectroscopy (EIS) in a region of low faradaic current. The incorporation of Cu and Ni significantly increased the surface area of cobalt oxide. The current density obtained from cyclic voltammetry (CV) data is reported as a function of the geometric and the real surface areas for each sample, which revealed that Co3O4 possesses the highest current density than other Cu or Cu and Ni-containing cobalt spinel oxides towards OER when corrected for differences in surface area. However, the addition of Cu could be viewed as beneficial as it provides a lower onset potential for OER and results in a relatively high current density compared to Co3O4. NixCu1-xCo2O4 materials have a similar current density per unit geometric area, however, when corrected for real surface area these electrodes display lower catalytic activity for OER than CuxCo3-xO4 (x = 0 to 1). The presence of a significant surface NiO species may have affected the catalytic activity of Ni-containing samples. The data will be discussed in the context of variable material performance found in the literature.

Revealing the effect of crystallinity and oxygen vacancies of Fe-Co phosphate on oxygen evolution for high-current water splitting

Strategically tuning the composition and structure of transition metal phosphates (TMPs) holds immense promise in the development of efficient oxygen evolution reaction (OER) electrocatalysts. However, the effect of crystalline phase transformation for TMPs on the catalytic OER activity remains relatively uncharted. In this study, we have deftly orchestrated the reaction process of anion-etched precursor to induce the amorphization process of FeCo-POx from crystalline to amorphous states. The as-obtained amorphous FeCo-POx (A-FeCo-POx) exhibited an optimized OER performance with a low overpotential of 270 mV at a current density of 10 mA cm−2, which could be attributed to the flexibility of its amorphous structure and the synergistic effect of oxygen vacancies. Moreover, when incorporated into an overall water splitting (OWS) device configured as A-FeCo-POx(+)||Pt/C(–), it displayed long-term solid stability, sustaining operation for 300 h at a current density of 200 mA cm−2. This work not only provides valuable insights into understanding the transformation from crystalline to amorphous states, but also establishes the groundwork for the practical utilization of amorphous nanomaterials in the field of water splitting.

High-valence metal-doped amorphous IrOx as active and stable electrocatalyst for acidic oxygen evolution reaction

Proton-exchange membrane water electrolysis, particularly driven by renewable electricity, is a sustainable strategy for green hydrogen production. However, developing highly active and stable electrocatalysts to accelerate the oxygen evolution reaction (OER) remains challenging. Herein, we introduce an effective strategy for constructing high-valence metal-doped IrOx with abundant oxygen vacancies, while simultaneously enhancing the catalytic activity and stability of the acidic OER. The synthesized Ta-doped IrOx (350-Ta@IrOx) exhibits ultramicroscopic nanoparticle morphology and abundant surface oxygen vacancies</a>, enabling a rapid OER process with a low overpotential of 223 mV at 10 mA cm-2 and 147.7 times higher mass activity (1207.4 A gIr−1) than that of commercial IrO2 at 1.55 V</a> versus the reversible hydrogen electrode. More importantly, 350-Ta@IrOx affords excellent stability with insignificant potential degradation after 500 h of electrolysis at 10 mA cm2, originating from the low operating potential and suppressed dissolution and oxidation of oxygen vacancy active sites via Ta doping. Density functional theory calculations suggest that Ta doping and oxygen defect engineering are effective in facilitating the nucleophilic attack of water molecules, thereby accelerating the rate-determining step toward high catalytic OER activity on Ta-doped IrOx. We anticipate that this study will provide an effective method to obtain active and stable electrocatalysts via high-valence metal doping.

Fabrication of carbon-coated Na/Fe@C nanorods using soybean straw for efficient oxygen evolution reaction catalysts

The oxygen evolution reaction (OER) process in water electrolysis requires high energy consumption. Reducing the interface limitations between metal and carbon precursors can significantly enhance the catalytic performance during the OER process. Because biomass exists in solid form, in this work, a carbon-coated Na/Fe@C nanorod OER electrocatalyst using soybean straw was prepared by coupling polyethylene glycol green liquefaction, in-situ doping, and carbonization route. The carbon coating increased the surface area and active site of the catalyst and prevented catalyst oxidation, thus extending the lifespan of the catalyst. The Na/Fe@C catalysts exhibited excellent OER catalytic activity. The overpotential at a current density of 10 mA cm−2 and 100 mA cm−2 were 275 and 320 mV, respectively. Therefore, this study provides a promising strategy for preparing stable electrocatalysts and reducing OER energy consumption.

Nitrogen-Doped Nickel Selenium Nanosheets for Highly Efficient Oxygen Evolution Reaction

Transition metal selenides have garnered considerable attention in the field of electrocatalytic oxygen evolution reaction (OER). However, their OER performances still lag behind those of Ir-based materials due to limited exposed active sites, inefficient electron transfer and inadequate stability. In this study, we have successfully synthesized nitrogen-doped NiSe2 nanosheets, which exhibit high efficiency and long-term stability for the OER, requiring only 320 mV to reach a current density of 10 mA cm−2. The nitrogen doping plays a crucial role in effectively regulating the work function and semiconductor characteristics of NiSe2, which facilitates the electron transport and optimizes the catalytic sites. Furthermore, the NiSe2 nanosheets present a larger surface area with more exposed active sites, thus resulting in exceptional OER catalytic activity. The nitrogen-doped NiSe2 nanosheets also display superior stability, maintaining a sustained current density throughout an 8-h OER operation.

A Ni-Fe-V trimetallic phosphorus-selenium composite supported on carbon cloth as freestanding electrocatalyst for oxygen evolution reaction

Developing highly active non-noble metal oxygen evolution reaction (OER) electrocatalysts is still urgent and significant to enable the large-scale hydrogen production. Herein, we propose a freestanding electrocatalyst of Ni-Fe-V trimetallic phosphorus-selenium composite on carbon cloth (NiV2P/FeSe@CC) for this issue, which is realized by the in-situ growth of V-MOF, the introduction of Ni and Fe components by electrodeposition, and the synchronous phosphatization and selenization treatment. The well-designed composite exhibits an excellent electrical conductivity and multi-level pore structure, which makes for rapid charge/mass transport and sufficient exposure of catalytic sites. The electrochemical deposition process allows Ni and Fe components to be uniformly deposited on the V-MOF, while the phosphorus and selenium co-doping can modulate the catalyst electronic structure and promote the adsorption of reaction intermediates, thus improving the OER catalytic activity. Consequently, the freestanding electrocatalyst exhibits an ultra-low overpotential of 168 mV under a current density of 10 mA cm−2 and a small Tafel slope of 44.32 mV dec-1 in alkaline environment. The outstanding performance is maintained in the integrated electrolyzer, presenting a small voltage of 1.53 V getting a current density of 10 mA cm−2 and an ultrastability for 160 h under 100 mA cm−2.