High-efficiency Oxygen Evolution Reaction Research Articles

One-Step Synthesis of High-Efficiency Oxygen Evolution Reaction Catalyst FeSx(Y/MB) with High Temperature Resistance and Strong Alkali

Given the energy crisis and escalating environmental pollution, the imperative for developing clean new energy is evident. Hydrogen has garnered significant attention owing to its clean properties, high energy density, and ease of storage and transportation. This study synthesized four types of catalysts—FeS(DI/MB), FeS(ET/MB), Fe(DI/MB), and Fe(ET/MB)—using two distinct solution systems: DI/MB and ET/MB. The FeS(DI/MB) catalyst, synthesized using the layered solution system (DI/MB), demonstrates a uniformly distributed and dense nanosheet structure, exhibiting excellent resistance to strong bases and superior catalytic properties. The FeS(DI/MB) electrode showed OER overpotentials of 460 mV and 318 mV in 1 M and 6 M, respectively, at current densities of up to 500 mA cm−2. Under industrial electrolysis test conditions, the FeS(DI/MB) electrode required only 262 mV to achieve a current density of 500 mA cm−2, operating in a high-temperature, strong alkaline environment of 6 M at 60 °C. Furthermore, the FeS(DI/MB) electrode exhibited excellent OER catalytic activity and stability, as evidenced by a 60 h stability test These findings provide valuable insights into the preparation of iron nickel sulfide-based catalysts, and further in-depth and comprehensive exploration is anticipated to yield the excellent catalytic performance of these catalysts in the realm of electrolytic water hydrogen production.

Super-hydrophilic electrode encapsulated lead halide-perovskite photoanode toward stable and efficient photoelectrochemical water splitting

Lead halide perovskites with excellent optoelectronic properties have been recognized as one of the most promising photoelectrode materials for photoelectrochemical water splitting during the past decade. However, fabricating stable and efficient halide-perovskite photoanodes remains a considerable challenge due to the degradation of halide perovskites in electrolyte environment and the lack of effective encapsulating techniques. Herein, we report a unique halide-perovskite photoelectrochemical cell by using an inverted fluorine-doped tin oxide coated glass (FTO/glass) as the waterproof hole-transport layer for encapsulation, and inserting a two-dimensional (2D) perovskite layer for passivation. The halide-perovskite photoanode achieves high-efficiency oxygen evolution reaction, fast bubble releasing and an outstanding long-term stability of 30.9 h at 90 % of the initial photocurrent density (up to 16.55 mA cm−2 at 1.23 V versus the reversible hydrogen electrode) under solar illumination. Our unique and cost-effective encapsulation method could be a potential solution for realizing stable and efficient halide-perovskite photoelectrodes for solar-fuel energy conversion.

Fluorine-decoration induced deep reconstruction of iron cobalt oxide for high-efficiency oxygen evolution reaction

The oxygen evolution reaction (OER) is a pivotal process in water electrolysis systems, yet developing cost-effective and highly active OER electrocatalysts from earth-abundant materials through straightforward methods remains a formidable challenge. In this study, FeCo oxides and their fluorides are synthesized using a one-step room-temperature process followed by fluorination with fluorine gas. We compared the OER performance of Fe, Co, and FeCo oxides and investigated the impact of fluorine doping on their physical properties and OER efficiency. Results revealed that the FeCo–O bimetallic oxide exhibited an overpotential of 370 mV in an alkaline electrolyte at a current density of 10 mA/cm2, significantly surpassing the performance of monometallic Fe–O (1 V) and Co–O (467 mV). Fluorine modification markedly enhanced the OER activity of these materials, with Fe-OF at 570 mV, Co-OF at 330 mV, and FeCo-OF at 285 mV. Notably, FeCo-OF demonstrated a stable overpotential lower than commercial RuO2 (289 mV) during a continuous 12 h OER test. Electrochemical analyses and spectral characterizations indicated that fluorine ion electronic regulation facilitated efficient electrocatalytic active sites in the spent FeCo-OF catalyst through in situ self-reconstruction, leading to its stable and superior OER performance. Density functional theory (DFT) calculations confirmed that fluorine modification of the bimetallic oxides decreased the O* Gibbs free energy from 4.86 to 2.44 eV, thereby enhancing the kinetics of the OER reaction.

Unraveling volcano trend in OER of metal–organic frameworks with asymmetric configuration through energy band engineering

Local symmetry breaking of catalysts has emerged as an effective strategy for finely tuning oxygen evolution reaction (OER) activity, yet the fundamental comprehension regarding asymmetric structure-activity relationships remains limited. Here, we propose the energy band engineering to bridge the correlation between established asymmetric electronic structure and adsorption/desorption ability of reaction intermediates within metal-organic frameworks (MOFs). The deliberate synthesis of CoM-MOFs (M=Cu, Ni, and Fe) with distinct coordination microenvironments enables the customization of asymmetric Co-O-M electronic structure. A volcano-shaped relationship can be revealed between calculated OER overpotential and average d‐band center (Ed) energy level for both active Co sites and substituted M. The CoFe-MOF, located close to the summit, showcases the balanced reaction intermediate behavior and thus for enhanced OER activity. This work presents a promising approach to thoroughly understand asymmetric electronic structure-activity relationships from the perspective of energy band engineering and further guide the discovery of high-efficiency MOF-based OER catalysts.

Microwave sintering construct 3D NiFeAl micro/nano porous bulk electrode for effective oxygen evolution reaction

The development of oxygen evolution reaction (OER) electrocatalysts is an important strategy to produce hydrogen energy by water splitting. Based on the Kirkendall effect and the capillary action of Al melting, this paper introduced a proper amount of Al into NiFe, and the 3D porous bulk high-efficiency OER electrodes were successfully prepared by microwave sintering. The 3D porous structure can provide abundant active sites for OER. The porous channel accelerates the penetration of O2 and electrolyte, shortens the diffusion path of reagents and products, and reduces the charge transfer resistance. It is worth noting that the NiFeAl porous bulk electrode shows excellent OER performance. The overpotentials are 205 mV and 251 mV at the current density of 10 mA cm−2 and 100 mA cm−2, respectively, and the Tafel slope is as low as 39.3 mV dec−1. Due to the existence of Al in the electrode and continuous etching and reconstruction in 1 M KOH solution, the stability test of the electrode lasts for more than 80 h, and the stability rate is even as high as 99.6%. In this work, a new view is put forward in developing an efficient and stable OER electrocatalysts for the preparation of transition metals.

Template-assisted strategy for synthesizing transition metal oxyhydroxide for high-efficiency oxygen evolution reaction

Oxyhydroxides have been widely recognized as the true active species for oxygen evolution reaction (OER), while most of them are created via the complicated and time-consuming electrochemical activation process. Here, we develop a facile template-mediated method for directly synthesizing highly active oxyhydroxides toward OER. The optimal FeCoOOH prepared via using Cu2O as a sacrificial template could exhibit outstanding electrocatalytic OER performance, delivering a current density of 10 mA cm−2 with the overpotential of merely 320 mV, and a corresponding Tafel slope of 77.5 mV dec−1. Detailed mechanism study outlines that the extraordinary OER performance of such FeCoOOH originated from the intrinsically high OER activity of oxyhydroxide and the high specific surface area of the particular architecture. This work demonstrates a simple and direct route for the successful fabrication of highly active oxyhydroxides, which may open a new way for the synthesis of other active species.

Tailored bimetallic synergy of iron–cobalt sulfide anchored to S-doped carbonized wood fiber for high-efficiency oxygen evolution reaction

Decoupling the scaling relation of intermediates is an effective strategy to improve the oxygen evolution reaction (OER) catalytic efficiency. Herein, S-doped carbon-confined Fe.92Co.08S nanoparticles (Fe.92Co.08S@SC) anchored to S-doped carbonized wood fiber (SCWF) are fabricated via simple synchronous carbonization and sulfidation. Due to the synergistic catalytic effect of bimetallic and the unique structural effect of the supported catalyst, Fe.92Co.08S@SC/SCWF exhibit excellent OER catalytic efficiency with an overpotential of 238 mV at 50 mA cm and stability up to 100 h. Furthermore, a high current density of 500 mA cm−2 at an overpotential of 281 mV was achieved. Theoretical calculations and electrochemical characterizations confirm that bimetallic synergies can accelerate the surface reconstruction of Fe.92Co.08S@SC with highly efficient OER activity. For zinc–air battery applications, Fe.92Co.08S@SC/SCWF exhibits superior power density and stability over commercial RuO2. This work provides insights into the preparation of supported electrocatalysts with bimetallic synergy for high-efficiency OER.

Spin-state regulation by secondary coordination sphere for improved oxygen evolution activity of LaCo1-xNixO3 perovskite

The evolution of oxygen evolution reaction (OER) remains a pivotal challenge in the realm of oxygen electrocatalysis. Recently, the proposition of regulating spin states has emerged as a novel avenue for enhancing the efficiency of electrocatalytic reactions. Presently, accurately modulating the metal active center into immediate spin (IS) remains a formidable challenge. Here, our research has achieved a breakthrough in precise spin state control and catalytic performance enhancement of Co3+ through the utilization of Ni-substituted LaCo1-xNixO3 perovskite. This achievement is primarily attributed to the fine regulation of both the secondary coordination sphere (SCS) and primary coordination sphere (PCS), i.e., Co6-y-[Co]-Niy (y = 0–6) and Co-O lengths, respectively. Our findings reveal that LaCo7/9Ni2/9O3 consisted of the SCS (y ≤ 2) with the eg1 fillings of IS Co3+ exhibits an optimal OER activity. Additionally, adjusting the Co-O bond length in PCS to approximately 1.89 Å proves to be more conducive to the transition of Co3+ spin states from high spin (HS) and low spin (LS) to IS. These discoveries present new approach to precisely modulating the spin state, offering promising prospects for the development of high-efficiency OER catalysts.

General Synthesis of Composition-Tunable High-Entropy Amorphous Oxides Toward High Efficiency Oxygen Evolution Reaction.

High-entropy materials have attracted much attention in the electrocatalysis field due to their unique structure, high chemical activity, and compositional tunability. However, the harsh and complex synthetic methods limit the application of such materials. Herein, a universal non-equilibrium liquid-phase synthesis strategy is reported to prepare high-entropy amorphous oxide nanoparticles (HEAO-NPs), and the composition of HEAO-NPs can be precisely controlled from tri- to ten-component. The non-equilibrium synthesis environment provided by an excessively strong reducing agent overcomes the difference in the reduction potentials of various metal ions, resulting in the formation of HEAO-NPs with a nearly equimolar ratio. The oxygen evolution reaction (OER) performance of HEAO-NPs is further improved by adjusting the composition and optimizing the electronic structure. The Fe16 Co32 Ni32 Mn10 Cu10 BOy exhibits a smaller overpotential (only 259mV at 10mAcm-2 ) and higher stability in OER compared with commercial RuO2 . The amorphous high-entropy structure with an optimized concentration of iron makes the binding energy of CoNi shift to a higher direction, promotes the generation of high-valence active intermediates, and accelerates the OER kinetic process. The HEAO-NPs have promising application potential in the field of catalysis, biology, and energy storage, and this work provides a general synthesis method for composition-controllable high-entropy materials.

Hollow CoVOx/Ag nanoprism with tailored electronic structure for high efficiency oxygen evolution reaction

Developing high-active and inexpensive electrocatalysts for oxygen evolution reaction (OER) is very important in the field of water splitting. The catalytic performance of electrocatalysts can be significantly improved by optimizing the electronic structure and designing suitable nanostructure. In this work, we represent the synthesis of hollow CoVOx/Ag-5 for OER. Due to the interaction of CoVOx and Ag nanoparticles, the electronic structure is optimized to improve the intrinsic catalytic activity. Additionally, the extrinsic catalytic activity of CoVOx/Ag is enhanced by the abundant active sites from the hollow structure. As a result, the CoVOx/Ag-5 demonstrates significantly enhanced OER catalytic activity with a low overpotential of 247 mV at 10 mA cm−2. In addition, it also exhibits excellent durability, without obvious attenuation in performance after continuous operation for 60 h. Furthermore, the catalyst can enable full water splitting with appropriate 100 % Faraday efficiency, demonstrating its practical application.

Nano-TiO2 anchored onto 2D Cu–Ni bimetallic MOF as a heterojunction for highly-efficient OER overpotential reduction

The heterojunction of TiO2 and MOF could effectively promote OER (overpotential (η = 10) is only 79 mV).

Understanding the synergistic catalysis effect on the dual-metal-N4 embedding single-walled carbon nanotubes from first principles

Developing high-efficiency electrocatalysts for the oxygen evolution reaction (OER) remains a crucial bottleneck on the way to the water splitting for producing clean fuel (H2). Compared with single atom catalysis (SACs), dual-atom catalysts (DACs) have attracted great interest due to higher OER catalytic efficiency. In this work, the OER properties of dual-metal-N4 embedding armchair single-walled carbon nanotubes (D-MN4/CNTs) were systematic studied by density functional theory (DFT) simulations. Our results indicate that CoN4 embedding armchair CNTs exhibit higher OER activity than the corresponding planar structure, especially for CoN4 embedding in armchair CNT (4, 4) (CNT4). For MN4-CoN4 co-embedding CNTs, the TiN4-CoN4/CNTs have good OER synergistic effect with the lowest overpotential. Besides, the diameter of CNTs have a significant impact on the OER efficiency. The lowest reaction overpotential 0.47 V were obtained in TiN4-CoN4/CNT4 with a 5.69 Å tube diameter. Interestingly, compressive stress will further enhance the synergistic effect between two metal atoms in the OER reaction. The OER overpotential of CoN4-TiN4 embedding armchair CNT4 can reduce to 0.40 V under the −4 % uniaxial compression strain. These works were expected to better understand the synergistic mechanisms and design high-efficiency dual-atom OER electrocatalysts.

Rational Construction of a Triple-Phase Reaction Zone Using CuO-Based Heterostructure Nanoarrays for Enhanced Water Oxidation Reaction.

The development of high-efficiency oxygen evolution reaction (OER) electrocatalysts for the production and conversion of clean energy is paramount yet also full of challenges. Herein, we proposed a simple and universal method to precisely fabricate the hierarchically structured CuO/TMOs loaded on Cu foil (CuO/TMOs/CF) (TMO represents Mn3O4, NiO, CoO, and CuO) nanorod-array electrodes as a highly active and stable OER electrocatalyst, employing Cu(OH)2/CF as a self-sacrificing template by the subsequent H2O2-induced chemical deposition (HiCD) and pyrolysis process. Taking CuO/Mn3O4/CF as an example, we systematically investigated its structure-performance relationship via experimental and theoretical explorations. The enhanced OER activity can be ascribed to the rational design of the nanoarray with multiple synergistic effects of abundant active sites, excellent electronic conductivity of the metallic Cu foil substrate, strong interface charge transfer, and quasi-superhydrophilic/superaerophobic property. Consequently, the optimal CuO/Mn3O4/CF presents an overpotential of 293 mV to achieve a current density of 20 mA cm-2 in 1.0 M KOH media, comparable to that of commercial RuO2 (282 mV), delivering excellent durability by the electrolysis of water at a potential of around 1.60 V [vs reversible hydrogen electrode (RHE)] without evident degeneration. This work might offer a feasible scheme for developing a hybrid nanoarray OER electrocatalyst via regulating electron transportation and mass transfer.

Determining the electrochemical activation mechanism of Prussian blue analog precatalysts for a high-efficiency oxygen evolution reaction

Determining the electrochemical activation mechanism of Prussian blue analog precatalysts for a high-efficiency oxygen evolution reaction

Nanoflower like FeNi–B–P based on bifunctional nickel foam as a binder free electrocatalyst for high-efficiency oxygen evolution reaction

Nickel foam as a current collector and substrate material is frequently utilized in electrochemical applications such as supercapacitors, batteries and the promising oxygen evolution reaction (OER). Herein, nanoflower like FeNi–B–P self-growing on nickel foam (FNBP/NF) is developed by electrodeposition and the B/P molar ratios within FNBP/NF are regulated to investigate the best OER performance at different ratios of boron and phosphorus. Moreover, the NF in this study achieves dual functionalization. It serves not only as a self-supporting formwork to maintain the intrinsic conductivity of the composite, but also as nickel source to provide attachment points and a growing environment. Thanks to the strong skeleton of NF, the catalyst shows extreme stability, as it remains almost constant during a 24 h chronopotentiometry test. Meanwhile, the convective effect of the NF prevents the accumulation of gas products at the interface, accelerating the precipitation of O2 and reducing contact resistance. Through electrochemical treatment, high-valence iron and nickel ions exhibit a synergistic effect that accelerates the coupling of O–O bonds, thereby promoting the evolution of O2. In 1.0 M KOH solution, the OER performance of FNBP/NF has been explored, when the current densities are 10 and 50 mA cm−2, the corresponding overpotentials are 253 and 318 mV, respectively, suggesting satisfactory electrocatalytic activity. Field emission scanning electron microscopy reveals a unique nanoflower-like morphology of FNBP/NF, providing abundant accessible sites for effective contact between the active substance and reactants. This study introduces bifunctional NF in OER catalysis to achieve dual synergistic effects, both synergistic effects of high-valence Fe–Ni ions and convective effect of NF, which accelerate O2 releasing and effectively reduce contact resistance, presenting a novel approach to achieving high-efficiency oxygen evolution.

Tuning the interface of MIMII(OH)F@MIMII1-xS (MⅠ: Ni, Co; MⅡ: Co, Fe) by atomic replacement strategy toward high performance overall water splitting

Constructing heterostructure is considered as one of the most promising strategies to reveal high efficiency hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance. Nevertheless, it is highly challenging to obtain stable interfaces and sufficient active sites via conventional method. In addition, Ni, Co and Fe elements share the valence electron structures of 3d6-84s2, the appropriate integration of these metals to induce synergistic effect in multicomponent electrocatalysts can enhance electrochemical activity. Herein, in this work, the MIMII(OH)F@MIMII1-xS (NiFe(OH)F@NiFe1-xS, NiCo(OH)F@NiCo1-xS, CoFe(OH)F@CoFe1-xS) autogenous heterostructure on nickel foam are constructed. As a result, NiFe(OH)F@NiFe1-xS-0.05, NiCo(OH)F@NiCo1-xS-0.05, and CoFe(OH)F@CoFe1-xS-0.05 demonstrate outstanding overpotential for HER (70 mV, 90 mV, 81 mV at −10 mA cm−2) and OER (370 mV, 470 mV, 370 mV at 10 mA cm−2) in alkaline electrolyte, while the overpotential for HER is 176 mV, 189 mV, 167 mV at −10 mA cm−2 and corresponding OER is 290 mV, 390 mV, 300 mV at 10 mA cm−2 in simulated seawater, respectively. In addition, the NiFe, NiCo, CoFe-based electrolyzer acquire favorable overall water splitting activity in alkaline (1.72 V, 1.87 V, 1.66 V) and simulated seawater (1.73 V, 1.75 V, 1.69 V) at 10 mA cm−2. Overall, the above results authenticate the feasibility of developing autogenous heterostructure electrocatalysts for providing hydrogen and oxygen in alkaline and simulated seawater.

Dual-path Fe migration in the bulk phase reconstructing high quality Ni-O-Fe units for high efficient oxygen evolution reaction

In the oxygen evolution reaction (OER), the non-reversible destruction of surface electronic structure caused by the irregular element migration in complex surface/interface reaction limits the improvement of catalyst’s activity and stability. Herein, we successfully realize the control of ‘dual-path migration of metallic elements in OER’ to stepwise reconstruct the O-coordinated bi-metal heterodimer (M1-O-M2) for electron density redistribution. By designing Fe@FeNi3 @NiO-Fe3O4 (F-FN-NFO) model electrode with stepwise surface treatment in OER process, the directional migration (from core to shell, path 1) and adjacent-surface migration of Fe atoms (path 2) are both controlled to reduce the formation energy of Ni-O-Fe units, realizing strengthened electron transfer between heterogeneous metal centers. After the surface reconstruction, the OER activity of F-FN-NFO increases for 8.6 times at 1.7 V (30.5–263 mA cm−2). Based on this strategy, the designed three-dimension NiFe@NiFexO is positive activated compared to traditional NiFe-oxidation with the overpotential reduced to 299 mV at 10 mA cm−2.

A hierarchical heterostructure NiCo-layered double hydroxide nanosheets/CoP nanowires/Ni foam for high-efficiency oxygen evolution reaction

Developing a hierarchical heterostructure is a feasible strategy to explore high-efficiency electrocatalysts for oxygen evolution reaction (OER). In this work, a hierarchical heterostructure was built by interface engineering between NiCo-LDH nanosheets and CoP nanowires. Their electronic structure is affected each other by a strong interaction due to the formed hierarchical heterostructure, regulating the intrinsic activity. CoP with a thin and long nanowire structure provides a large electrochemical active area. With these advantages, the prepared NiCo-LDH nanosheets/CoP nanowires/Ni foam shows an enhanced oxygen evolution reaction (OER) performance with an overpotential of 253 mV at 10 mA·cm−2 in an alkaline environment (1 M KOH). This paper provides a potential strategy for high-efficiency oxygen evolution reaction (OER).

Electronic-ferry in metal element migration promoting deep activation of NiFe based phosphide for high efficient and stable oxygen evolution reaction

The design principle of high-efficient water electrolysis catalysis in oxygen evolution reaction (OER) has been primarily focused on the construction of multi-metal active centres. However, the spatial barrier between nonadjacent metal sites restricts the electron transfer, thus limits the activation and stability of active sites for improving the OER performance. Herein, a concept of electronic-ferry strategy by metal element migration in OER reconstruction is adopted to form dynamic electron-bridge between heterogeneous metal ions, which synchronously improves the OER kinetics and the corrosion resistance of metals centres. By designing layered NiCrP@NiFeP with concentration gradient, Cr element stepwise-release from the core part endows electron-ferry along the path of Ni2+-Cr4+/Ni3+-Cr6+ and Cr3+-Fe4+, achieving deep activated Ni(Fe)OOH layer with highly stable Fe sites in OER reconstruction process. The reconstructed NiCrP@NiFeP electrode shows 270 mV overpotential at 100 mA cm−2 current density with steady working more than 2600 h.

High-Efficiency Oxygen Evolution Reaction: Controllable Reconstruction of Surface Interface.

The precatalyst undergoes surface reconstruction during the oxygen evolution reaction (OER) process, and the reconstituted material is the one that really plays a catalytic role. However, the degree of surface reconstruction seriously affects the catalytic performance. For this reason, it is important to establish the link between the degree of reconstruction and catalytic activity based on a deep understanding of the OER mechanism for the rational design of high-performance OER electrocatalysts. Here, the reaction mechanism of OER is briefly introduced, the competition between adsorbate evolution mechanism (AEM) mechanism and lattice oxygen-mediated mechanism (LOM) mechanism is discussed, and several activity descriptors of OER reaction are summarized. The strategies to realize OER controllable surface reconstruction are emphatically introduced, including ion leaching, element doping, regulating catalyst size, heterogeneous structure engineering, and self-reconstruction. A mechanistic perspective is emphasized to understand the relationship between dynamic surface reconstruction and electronic structure. Controlled reconfiguration of OER surface can break the limitation of proportional relationship brought by traditional AEM mechanism, also can realize the switching between AEM mechanism and LOM mechanism, thus realizing ultra-low overpotential. This review will provide some reference for surface controllable reconstruction of OER transition metal-based catalysts and reasonable development of ideal catalytic performance.