Durable Oxygen Evolution Reaction Research Articles

Combustion Growth of NiFe Layered Double Hydroxide for Efficient and Durable Oxygen Evolution Reaction.

NiFe layered double hydroxide (LDH) with abundant heterostructures represents a state-of-the-art electrocatalyst for the alkaline oxygen evolution reaction (OER). Herein, NiFe LDH/Fe2O3 nanosheet arrays have been fabricated by facile combustion of corrosion-engineered NiFe foam (NFF). The in situ grown, self-supported electrocatalyst exhibited a low overpotential of 248 mV for the OER at 50 mA cm-2, a small Tafel slope of 31 mV dec-1, and excellent durability over 100 h under the industrial benchmarking 500 mA cm-2 current density. A balanced Ni and Fe composition under optimal corrosion and combustion contributed to the desirable electrochemical properties. Comprehensive ex-situ analyses and operando characterizations including Fourier-transformed alternating current voltammetry (FTACV) and in situ Raman demonstrate the beneficial role of modulated interfacial electron transfer, dynamic atomic structural transformation to NiOOH, and the high-valence active metal sites. This study provides a low-cost and easy-to-expand way to synthesize efficient and durable electrocatalysts.

Shifting the Oxygen-Evolution Reaction Pathway via Cation Engineering to Activate Lattice Oxygen in Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) as promising electrocatalysts have been widely studied, but their performance is limited by conductivity and coordinating saturation. This study proposes a cationic (V) modification strategy and evaluates its effect on the electrocatalytic performance of CoFe-MOF nanosheet arrays. The optimal V-CoFe-MOF/NF electrocatalyst exhibits excellent oxygen-evolution reaction (OER)/hydrogen-evolution reaction (HER) performance (231 mV at 100 mA cm-2/86 mV at 10 mA cm-2) in alkaline conditions, with its OER durability exceeding 400 h without evident degradation. Furthermore, as a bifunctional electrocatalyst for water splitting, a small cell voltage is achieved (1.60 V at 10 mA cm-2). The practicability of the catalyst is further evaluated by membrane electrode assembly (MEA), showing outstanding activity (1.53 V at 10 mA cm-2) and long-term stability (at 300 mA cm-2). Moreover, our results reveal the apparent reconstruction properties of V-CoFe-MOF/NF in alkaline electrolytes, where the partially dissolved V promotes the formation of more active β-MOOH. The mechanism study shows the OER mechanism shifts to a lattice oxygen oxidation mechanism (LOM) after V doping, which directly avoids complex multistep adsorption mechanism and reduces reaction energy. This study provides a cation mediated strategy for designing efficient electrocatalysts.

Self-supported Ru-Fe-Ox nanospheres as efficient electrocatalyst to boost overall water-splitting in acid and alkaline media

Developing electrocatalysts with high activity and durability for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in both acidic and alkaline electrolytes remains challenging. In this study, we synthesize a self-supported ruthenium-iron oxide on carbon cloth (Ru-Fe-Ox/CC) using solvothermal methods followed by air calcination. The morphology of the nanoparticle exposes numerous active sites vital for electrocatalysis. Additionally, the strong electronic interaction between Ru and Fe enhances electrocatalytic kinetics optimization. The porous structure of the carbon cloth matrix facilitates mass transport, improving electrolyte penetration and bubble release. Consequently, Ru-Fe-Ox/CC demonstrates excellent catalytic performance, achieving low overpotentials of 32 mV and 28 mV for HER and 216 mV and 228 mV for OER in acidic and alkaline electrolytes, respectively. Notably, only 1.48 V and 1.46 V are required to reach 10 mA cm−2 for efficient water-splitting in both mediums, exhibiting remarkable stability. This research offers insights into designing versatile, highly efficient catalysts suitable for varied pH conditions.

Mn-doped Sequentially Electrodeposited Co-based Oxygen Evolution Catalyst for Efficient Anion Exchange Membrane Water Electrolysis.

Designing high-performance and durable oxygen evolution reaction (OER) catalysts is important for green hydrogen production through anion exchange membrane water electrolysis (AEMWE). Herein, a series of Mn-doped Co-based OER catalysts supported on FeOxHy (FCMx) are presented to enhance the OER activity. Mn doping effectively reduces the size of the Co oxide particles, thereby augmenting the active surface area. Moreover, Mn doping induces the creation of oxygen vacancies, leading to an efficient structural conversion during the OER, which is confirmed via in situ Raman spectroscopy. Under optimal conditions, the catalyst exhibits an overpotential of 234.4 mV at 10 mA cm-2 and a Tafel slope of 37.2 mV dec-1 under half-cell conditions. The AEMWE single-cell system demonstrates a current density of 1560 mA cm-2 at 1.8 V at 60 °C with a degradation rate of 0.4 mV h-1 for 500 h at 500 mA cm-2. Our development of a robust OER catalyst represents notable progress in the field of nonprecious-metal water electrolysis, marking a step toward cost-effective green hydrogen production.

Ruthenium-Based Binary Alloy with Oxide Nanosheath for Highly Efficient and Stable Oxygen Evolution Reaction in Acidic Media.

Traditional noble metal oxide, such as RuO2, is considered a benchmark catalyst for acidic oxygen evolution reaction (OER). However, its practical application is limited due to sluggish activity and severe electrochemical corrosion. In this study, Ru-Fe nanoparticles loading on carbon felt (RuFe@CF) is synthesized via an ultrafast Joule heating method as an active and durable OER catalyst in acidic conditions. Remarkably low overpotentials of 188 and 269mV are achieved at 10 and 100mA cm-2, respectively, with a robust stability up to 620 h at 10mA cm-2. When used as an anode in a proton exchange membrane water electrolyzer, the catalyst shows more than 250 h of stability at a water-splitting current of 200mA cm-2. Experimental characterizations reveal the presence of a Ru-based oxide nanosheath on the surface of the catalyst during OER tests, suggesting a surface reconstruction process that enhances the intrinsic activity and inhibits continuous metal dissolution. Moreover, density functional theory calculations demonstrate that the introduction of Fe into the RuFe@CF catalyst reduces the energy barrier and boosts its activities. This work offers an effective and universal strategy for the development of highly efficient and stable catalysts for acidic water splitting.

Synthesis of CNT/Ru/Cobalt oxide composites as oxygen evolution reaction electrocatalysts via ball milling approach

Ruthenium (Ru) and Cobalt oxides (CoO) nanoparticles are uniformly decorated on surfaces of carbon nanotubes (CNTs), via ball milling of mixtures consisting of commercial CNTs, triphenylphosphine ruthenium chlorides and Cobalt nitrates. Due to collective contributions of Ru and CoO, the obtained CNT/Ru/CoO composites exhibit excellent electrocatalytic activities and durability for oxygen evolution reaction (OER), both of which outperform those of the state-of-the-art iridium oxide catalysts.

Photo-assisted electrocatalysis of NiO/CeO2 heterojunction for efficient oxygen evolution reaction

In recent years, photo-assisted electrocatalysis has attracted significant interest in the field of electrolytic hydrogen production. By integrating electrical and optical energy, supplementary energy is harnessed for the electrocatalytic process, which offers an efficient strategy to enhance the performance of oxygen evolution reaction (OER). Herein, the heterojunction NiO/CeO2 composite nanostructures supported by nickel foam (represented as NiO/CeO2@NF) was selected as the photo-assisted electrocatalyst, through the mutual synergy of voltage and light to improve the catalytic activity of OER in electrolytic water. Under light irradiation, the NiO component undergoes photoexcited to produce photogenerated electrons that move towards the CeO2 component, stimulating the generation and accumulation of more holes accelerating the formation of Ni (III) to improve the reaction efficiency with electrons, thereby boosting the enhancement of OER activity. The results demonstrate that the overpotential corresponding to NiO/CeO2@NF in non-irradiation at 10 mA cm−2 current density was 280 mV, and the NiO/CeO2@NF in light irradiation displays robust OER activity, with lower over-potentials 260 mV at 10 mA cm−2, which 20 mV lower than in non-irradiation. Moreover, NiO/CeO2@NF in light irradiation exhibits high catalytic activity and durability for OER in an alkaline electrolyte, delivering 100 mA cm−2 at 320 mV and outperforming RuO2 under high current densities.

Electronic structure control of IrO2 via conjugated polymer support for highly efficient oxygen evolution reaction

In this paper, we report synthesis of novel nanoparticle catalyst of iridium oxide supported on conjugated polymer along with evaluation of activity and durability for oxygen evolution reaction. The IrO2/poly(BIAN-thiophene)/TNT catalyst was prepared from iridium complex and poly(BIAN-thiophene)/TNT by hydrothermal method. The synthesized IrO2/poly(BIAN-thiophene)/TNT catalysts was characterized by scanning electron microscopy, transmission electron microscopy, Fourier transfer-infrared spectroscopy, x-ray photoelectron spectroscopy and electrochemical methods. The average particle size of the IrO2 particles on poly(BIAN-thiophene)/TNT was 2.5 nm. The XPS measurement revealed that Ir complex was completely converted to iridium oxide through hydrothermal treatment. The IrO2/poly(BIAN-thiophene)/TNT catalyst showed sufficient performance for OER activity and durability in acidic condition. Our results indicate that IrO2/poly(BIAN-thiophene)/TNT is one of the prospective candidate catalysts for water splitting.

Synthesis of graphene/Ru/NiO composites as highly active oxygen evolution reaction electrocatalysts

Graphene nanoplates which are decorated uniformly with ruthenium (Ru) and nickel oxide (NiO) nanoparticles, are fabricated via ball milling of graphite, triphenylphosphine ruthenium chlorides and nickel chlorides. Electrochemical measurement results demonstrate that the resultant graphene/Ru/NiO composites deliver a lower overpotential of 240 mV at current density of 10 mA cm−2 and better durability for oxygen evolution reaction (OER) than the state-of-the-art iridium oxide catalysts. The superior OER performances of the graphene/Ru/NiO composites are attributed to collective contributions of Ru and NiO.

Rapid Conversion from Alloy Nanoparticles to Oxide Nanowires: Strain Wave-Driven Ru-O-Mn Collaborative Catalysis for Durable Oxygen Evolution Reaction.

Metal-doped ruthenium oxides with low prices have gained widespread attention due to their editable compositions, distorted structures, and diverse morphologies for electrocatalysis. However, the mainstream challenge lies in breaking the so-called seesaw relationship between activity and stability during acidic oxygen evolution reaction (OER). Herein, strain wave-featured Mn-RuO2 nanowires (NWs) with asymmetric Ru-O-Mn bonds are first fabricated by thermally driven rapid solid phase conversion from RuMn alloy nanoparticles (NPs) at moderate temperature (450 °C). In 0.5M H2 SO4 , the resultant NWs display a surprisingly ultralow overpotential of 168mV at 10mA cm-2 and run at a stable cell voltage (1.67V) for 150h at 50mA cm-2 in PEMWE, far exceeding IrO2 ||Pt/C assemble. The simultaneous enhancement of both activity and stability stems from the presence of dense strain waves composed of alternating compressive and tensile ones in the distorted NWs, which collaboratively activate the Ru-O-Mn sites for faster OER. More importantly, the atomic strain waves trigger dynamic Ru-O-Mn regeneration via the refilling of oxygen vacancies by oxyanions adsorbed on adjacent Mn and Ru sites, achieving long-term stability. This work opens a door to designing non-precious metal-assisted ruthenium oxides with unique strains for practical application in commercial PEMWE.

Three-dimensional ordered macroporous design of heterogeneous cobalt–iron phosphides as oxygen evolution electrocatalyst

Oxygen evolution reaction (OER) plays a key role in electrochemical conversion, which needs efficient and economical electrocatalyst to boost its kinetics for large-scale application. Herein, a bimetallic CoP/FeP2 heterostructure with a three-dimensional ordered macroporous structure (3DOM-CoP/FeP2) was synthesized as an OER catalyst to demonstrate a heterogeneous engineering induction strategy. By adjusting the electron distribution and producing a lot of active sites, the heterogeneous interface enhances catalytic performance. High specific surface area is provided by the 3DOM structure. Additionally, at the solid–gas-electrolyte threephase interface, the electrocatalytic reaction exhibits good mass transfer. In sit u Raman spectroscopy characterization revealed that FeOOH and CoOOH reconstructed from CoP/FeP2 were the true OER active sites. Consequently, the 3DOM-CoP/FeP2 demonstrates superior OER activity with a low overpotentials of 300/420 mV at 10/100 mA cm–2 and meritorious OER durability. It also reveals promising performance as the overall water splitting anode.

Challenges and progress in oxygen evolution reaction catalyst development for seawater electrolysis for hydrogen production.

Production of green hydrogen on a large scale can negatively impact freshwater resources. Therefore, using seawater as an electrolyte in electrolysis is a desirable alternative to reduce costs and freshwater reliance. However, there are limitations to this approach, primarily due to the catalyst involved in the oxygen evolution reaction (OER). In seawater, the OER features sluggish kinetics and complicated chemical reactions that compete. This review first introduces the benefits and challenges of direct seawater electrolysis and then summarises recent research into cost-effective and durable OER electrocatalysts. Different modification methods for nickel-based electrocatalysts are thoroughly reviewed, and promising electrocatalysts that the authors believe deserve further exploration have been highlighted.

Sr-Stabilized IrMnO2 Solid Solution Nano-Electrocatalysts with Superior Activity and Excellent Durability for Oxygen Evolution Reaction in Acid Media.

The development of cost-effective catalysts for oxygen evolution reaction (OER) in acidic media is of paramount importance. This work reports that Sr-doped solid solution structural ultrafine IrMnO2 nanoparticles (NPs) (≈1.56nm) on the carbon nanotubes(Sr-IrMnO2/CNTs) are efficient catalysts for the acidic OER. Even with the Ir use dosage 3.5 times lower than that of the commercial IrO2, the Sr-IrMnO2/CNTs only need an overpotential of 236.0mV to drive 10.0mA cm-2 and show outstanding stability for >400.0 h. Its Ir mass activity is 39.6 times higher than that of the IrO2 at 1.53V. The solid solution and Sr-doping structure of Sr-IrMnO2 are the main origin of the high catalytic activity and excellent stability of the Sr-IrMnO2/CNTs. The density function theory calculations indicate that the solid solution structure can promote strong electronic coupling between Ir and Mn, lowering the energy barrier of the OER rate-determining step. The Sr-doping can enhance the stability of Ir against the chemical corrosion and demetallation. Water electrolyzers and proton exchange membrane water electrolyzers assembled with the Sr-IrMnO2/CNTs show superb performance and excellent durability in the acid media.

Controlled fabrication of Fe3N@NG composites as superior oxygen evolution reaction electrocatalysts

We report the controlled fabrication of nitrogen doped graphene (NG) nanoplates, which are uniformly decorated with iron nitride (Fe3N) nanoparticles, via ball milling of mixtures of graphite and iron nitrates and the following ammonia annealing. The obtained Fe3N@NG composites demonstrate excellent electrocatalytic activity and durability for oxygen evolution reaction, both of which outperform those of the state-of-the-art iridium oxide catalysts. This may be attributed to nitrogen doping as well as the synergistic effect between Fe3N and graphene nanoplates.

In Situ Regulating Cobalt/Iron Oxide-Oxyhydroxide Exchange by Dynamic Iron Incorporation for Robust Oxygen Evolution at Large Current Density.

The key dilemma for green hydrogen production via electrocatalytic water splitting is the high overpotential required for anodic oxygen evolution reaction (OER). Co/Fe-based materials show superior catalytic OER activity to noble metal-based catalysts, but still lag far behind the state-of-the-art Ni/Fe-based catalysts probably due to undesirable side segregation of FeOOH with poor conductivity and unsatisfied structural durability under large current density. Here, a robust and durable OER catalyst affording current densities of 500 and 1000mA cm-2 at extremely low overpotentials of 290 and 304mV in base is reported. This catalyst evolves from amorphous bimetallic FeOOH/Co(OH)2 heterostructure microsheet arrays fabricated by a facile mechanical stirring strategy. Especially, in situ X-ray photoelectron spectroscopy (XPS) and Raman analysis decipher the rapid reconstruction of FeOOH/Co(OH)2 into dynamically stable Co1-x Fex OOH active phase through in situ iron incorporation into CoOOH, which perform as the real active sites accelerating the rate-determining step supported by density functional theory calculations. By coupling with MoNi4 /MoO2 cathode, the self-assembled alkaline electrolyzer can deliver 500mAcm-2 at a low cell voltage of 1.613V, better than commercial IrO2 (+) ||Pt/C(-) and most of reported transition metal-based electrolyzers. This work provides a feasible strategy for the exploration and design of industrial water-splitting catalysts for large-scale green hydrogen production.

Facile one-step deposition of nanosized Ni(OH)2–MoS2 heterostructure electrodes for efficient oxygen evolution reaction

There is an increasing need for environmentally friendly and sustainable energy sources that rely on efficient and abundant electrocatalysts for the oxygen evolution reaction (OER). OER plays a key role in energy conversion and storage applications. Using a vacuum kinetic spray technique operating at room temperature, electrocatalysts based on nano-sized Ni(OH)2–MoS2 nanocomposites (NCs) on nickel foam are fabricated from the corresponding micron powders. The Ni(OH)2–MoS2 NC modified working electrodes were exploited to investigate the OER at different weight ratios of MoS2 (25, 50, and 75 wt%). To comprehensively investigate and elucidate the surface state and morphology of the electrode, x-ray diffraction, scanning electron microscopy (SEM), Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS) were assessed. SEM images showed that the micro-sized particles were fragmented into smaller nanoscale particles. XPS spectra revealed the synergy enhancement in the Ni(OH)2–MoS2 NCs that resulted in a strong improvement in the OER activity. Ni(OH)2–MoS2 hybrid NCs with 75 wt% MoS2 exhibited the lowest overpotential of 282 mV at 10 mA cm−2 and a small Tafel slope of 54 mV⋅dec−1. Alongside, the prolonged OER durability at 50 mA cm−2 is verified for up to 50 h.

Nickel-cobalt phosphide nanowires as precatalysts for surface reconstruction to prepare durable and efficient OER catalysts

The investigation of transition metal phosphides (TMPs) as efficient electrocatalysts for water splitting has garnered significant attention in academic research. Nevertheless, limited research has been conducted on the alteration of the structural and morphological properties of TMPs resulting from the unavoidable surface reconstruction during the oxygen evolution reaction (OER). This study introduces a newly developed catalyst, namely nickel–cobalt phosphide nanowires (NiCoP), which facilitates the in-situ growth of nickel–cobalt oxide (NiCo2O4) through surface reconstruction during anodic potential cycling in alkaline electrolytes. The catalyst's extensive modification can be observed through ex-situ characterization techniques. The catalyst undergoes a significant transformation that ultimately yields a phosphide scaffold, leading to the formation of a spinel oxide surface. This transformation enhances the catalytic environment for the OER, making it highly efficient and potent. The transformed catalyst demonstrates comparable catalytic performance to the precious RuO2 catalyst across various current densities. Importantly, it exhibits remarkable long-term stability, as demonstrated by its ability to sustain continuous operation for 72 h at a current density of 50 mA while maintaining stable catalytic performance.

High-Performance Alkaline Seawater Electrolysis with Anomalous Chloride Promoted Oxygen Evolution Reaction.

A highly selective and durable oxygen evolution reaction (OER) electrocatalyst is the bottleneck for direct seawater splitting because of side reactions primarily caused by chloride ions (Cl-). Most studies about OER catalysts in seawater focus on the repulsion of the Cl- to reduce its negative effects. Herein, we demonstrate that the absorption of Cl- on the specific site of a popular OER electrocatalyst, nickel-iron layered double hydroxide (NiFe LDH), does not have a significant negative impact; rather, it is beneficial for its activity and stability enhancement in natural seawater. A set of in situ characterization techniques reveals that the adsorption of Cl- on the desired Fe site suppresses Fe leaching, and creates more OER-active Ni sites, improving the catalyst's long-term stability and activity simultaneously. Therefore, we achieve direct alkaline seawater electrolysis for the very first time on a commercial-scale alkaline electrolyser (AE, 120 cm2 electrode area) using the NiFe LDH anode. The new alkaline seawater electrolyser exhibits a reduction in electricity consumption by 20.7 % compared to the alkaline purified water-based AE using commercial Ni catalyst, achieving excellent durability for 100 h at 200 mA cm-2.

High‐Performance Alkaline Seawater Electrolysis with Anomalous Chloride Promoted Oxygen Evolution Reaction

AbstractA highly selective and durable oxygen evolution reaction (OER) electrocatalyst is the bottleneck for direct seawater splitting because of side reactions primarily caused by chloride ions (Cl−). Most studies about OER catalysts in seawater focus on the repulsion of the Cl− to reduce its negative effects. Herein, we demonstrate that the absorption of Cl− on the specific site of a popular OER electrocatalyst, nickel‐iron layered double hydroxide (NiFe LDH), does not have a significant negative impact; rather, it is beneficial for its activity and stability enhancement in natural seawater. A set of in situ characterization techniques reveals that the adsorption of Cl− on the desired Fe site suppresses Fe leaching, and creates more OER‐active Ni sites, improving the catalyst's long‐term stability and activity simultaneously. Therefore, we achieve direct alkaline seawater electrolysis for the very first time on a commercial‐scale alkaline electrolyser (AE, 120 cm2 electrode area) using the NiFe LDH anode. The new alkaline seawater electrolyser exhibits a reduction in electricity consumption by 20.7 % compared to the alkaline purified water‐based AE using commercial Ni catalyst, achieving excellent durability for 100 h at 200 mA cm−2.

Valence engineering via double exchange interaction in spinel oxides for enhanced oxygen evolution catalysis

The design of spinel-oxide-based catalysts with high activity and long-term durability for oxygen evolution reaction (OER) confronts grand challenges that may be well tackled by maneuvering the electronic structure of surface catalytic sites within spinel oxides. Herein, we harness a double exchange interaction (DEI) triggered by the synergistic effects of Schottky junction and oxygen vacancies (VO) to generate high proportions of octahedrally coordinated Ni3+ and Co2+ (highly active sites) in the edge-sharing [NixCo1−XO6] octahedra. Specifically, Schottky junction is formed between metallic Cu nanowires and semiconducting NiCo2O4 via a core-shell structure, and abundant VO sites are created in NiCo2O4 via H2 thermal treatment. As expected, the Cu@VO-NiCo2O4 electrocatalyst allows a significantly boosted OER performance, with a low overpotential of 214 mV at 10 mA cm-2 and a small Tafel slope of 64.9 mV dec-1, which outperforms the state-of-the-art RuO2 catalyst and most of reported Ni-Co based OER catalysts. Our work provides some inspirations for designing high-performance spinel-oxide-based electrocatalysts towards OER via DEI engineering.