Oxygen Evolution Reaction Catalysts Research Articles

Formation of Core‐Shell Ir@TiO2 Nanoparticles through Hydrogen Treatment as Acidic Oxygen Evolution Reaction Catalysts

Formation of Core‐Shell Ir@TiO₂ Nanoparticles through Hydrogen Treatment as Acidic Oxygen Evolution Reaction Catalysts

3D carbon corrosion kinetic mechanism modeling study for proton exchange membrane fuel cells under localized flooding

Localized anode flooding often occurs in proton exchange membrane fuel cells (PEMFCs) during operation, which leads to localized H2 deficiency and triggers the carbon support corrosion in the catalyst layer, thus seriously weakening the performance and service life of PEMFCs. In this work, a 3D carbon corrosion kinetic mechanism model under localized anode flooding is developed to analyze in detail the multi-physics field distributions during carbon corrosion. The developed model is also coupled with a PEMFC performance model to focus on the carbon corrosion rate spatial distribution and its effect on the PEMFC performance. In addition, the effect of the cathode catalyst layer (CCL) added with oxygen evolution reaction (OER) catalyst on the carbon corrosion rate is analyzed in detail. Considering the particularly expensive OER catalysts and the non-uniform carbon corrosion distribution, a scheme of multi-area ordered adding with OER catalysts is further proposed to reduce the OER catalyst loading, and it is found that such a scheme can more effectively reduce the non-uniform carbon corrosion within the CCL. The electrochemical surface area loss is reduced by 7.38 % and the performance is improved by 5.69 % with scheme 2 compared to without the addition of OER catalyst.

Transition metal doped into layered double hydroxide as efficient electrocatalysts for oxygen evolution reaction: A DFT study

The doping of transition metal (TM) into layered double hydroxide (LDH) is a widely used method for developing efficient and durable electrocatalysts for the oxygen evolution reaction (OER). In this study, a series of TM-doped bimetallic LDH (TMII/TMIII@M3N-LDH(110)) models were constructed and their OER properties were systematically evaluated using density functional theory (DFT) calculations. Furthermore, the overall volcano plot was constructed, from which seven potential OER catalysts were screened out. Among them, PtIII@Co3Fe-LDH(110) and RuII@Co3Fe-LDH(110) were identified as the most promising candidates, exhibiting excellent OER performance with a theoretical overpotential (ηOER) of 0.20 V, and were analyzed for the doping effect of TM by electronic structure. The results demonstrated that TM doped into M3N-LDH(110) plays a crucial role in the OER process. These theoretical studies not only pave the way for further exploration of efficient OER catalysts but also illustrate the potential of trimetallic LDH as high-performance catalysts.

S-doped amorphous multi-metal borophosphates for efficient alkaline seawater oxidation with a high corrosion resistance

Direct seawater splitting is a promising strategy for the production of green hydrogen to address water shortage and environmental concerns. However, the primary obstacle in direct seawater splitting is directly related to the high selectivity and durability of oxygen evolution reaction (OER) electrocatalysts. In this study, we developed sulfur-doped multimetal (Ni, Fe, and Co) borophosphates (BPOs) as high-performance OER catalysts for alkalized seawater electrolytes. The incorporated sulfur atoms act as precursors to enhance the corrosion resistance, as they form negatively charged polyanionic surface layers that block the chloride ions. The best catalyst demonstrates an overpotential of 278 mV in alkaline freshwater and 292 mV in alkalized seawater electrolytes when subjected to a current density of 100 mA cm−2. The overpotential disparity between the two media was only 14 mV, suggesting that the material has substantial resistance to chloride corrosion. Furthermore, excellent electrochemical durability was attained for the sulfurized and amorphized multi-metal BPOs, highlighting their high potential as promising catalysts for seawater oxidation.

Regulating Strain and Electronic Structure of Indium Tin Oxide Supported IrOx Electrocatalysts for Highly Efficient Oxygen Evolution Reaction in Acid.

The development of proton exchange membrane water electrolysis is a promising technology for hydrogen production, which has always been restricted by the slow kinetics of the oxygen evolution reaction (OER). Although IrOx is one of the benchmark acidic OER electrocatalysts, there are still challenges in designing highly active and stable Ir-based electrocatalysts for commercial application. Herein, a Ru-doped IrOx electrocatalyst with abundant twin boundaries (TB-Ru0.3Ir0.7Ox@ITO) is reported, employing indium tin oxide with high conductivity as the support material. Combing the TB-Ru0.3Ir0.7Ox nanoparticles with ITO support could expose more active sites and accelerate the electron transfer. The TB-Ru0.3Ir0.7Ox@ITO exhibits a low overpotential of 203 mV to achieve 10 mA cm-2 and a high mass activity of 854.45 A g-1noblemetal at 1.53 V vs RHE toward acidic OER, which exceeds most reported Ir-based OER catalysts. Moreover, improved long-term stability could be obtained, maintaining the reaction for over 110 h at 10 mA cm-2 with negligible deactivation. DFT calculations further reveal the activity enhancement mechanism, demonstrating the synergistic effects of Ru doping and strains on the optimization of the d-band center (εd) position and the adsorption free energy of oxygen intermediates. This work provides ideas to realize the trade-off between high catalytic activity and good stability for acidic OER electrocatalysts.

Guided Heterostructure Growth of CoFe LDH on Ti3C2Tx MXene for Durably High Oxygen Evolution Activity.

Heterostructures of layered double hydroxides (LDHs) and MXenes have shown great promise for oxygen evolution reaction (OER) catalysts, owing to their complementary physical properties. Coupling LDHs with MXenes can potentially enhance their conductivity, stability, and OER activity. In this work, a scalable and straightforward in situ guided growth of CoFeLDH on Ti3C2Tx is introduced, where the surface chemistry of Ti3C2Tx dominates the resulting heterostructures, allowing tunable crystal domain sizes of LDHs. Combined simulation results of Monte Carlo and density functional theory (DFT) validate this guided growth mechanism. Through this way, the optimized heterostructures allow the highest OER activity of the overpotential = 301mV and Tafel slope = 43mV dec-1 at 10mA cm-2, and a considerably durable stability of 0.1% decay over 200h use, remarkably outperforming all reported LDHs-MXenes materials. DFT calculations indicate that the charge transfer in heterostructures can decrease the rate-limiting energy barrier for OER, facilitating OER activity. The combined experimental and theoretical efforts identify the participation role of MXene in heterostructures for OER reactions, providing insights into designing advanced heterostructures for robust OER electrocatalysis.

Recent advantages on mass transfer structure construction in transition metal‐based cost‐effective catalyst toward alkaline oxygen evolution

The electrochemical oxygen evolution reaction (OER) can be combined with various reactions to fabricate electrochemical energy conversion and storage devices while the slow kinetics and poor mass transfer capability at high current densities were the key constraints to its large‐scale application. Therefore, this review primarily focuses on design and optimization of mass transfer structures of TM‐metal‐based OER catalysts. Nanostructuring, porous design, and the creation of hierarchical architectures have been applied during catalyst synthesis to enhance the surface area and accessibility, thereby improving mass transfer and catalytic OER efficiency. Strategies including doping, substrate invitation, soft/hard templating has been utilized to accelerate mass transfer as well as the ion/electron conduction efficiency for the overall improvement of OER performance of the catalysts. These developments underline the critical role of advanced material design in achieving high‐performance OER catalysts and highlight the potential of TM‐based materials in cost‐effective and scalable applications.

Cr dopant mediates hydroxyl spillover on RuO2 for high-efficiency proton exchange membrane electrolysis

Simultaneously improving the activity and stability of catalysts for anodic oxygen evolution reaction (OER) in proton exchange membrane water electrolysis (PEMWE) remains a notable challenge. Here, we report a chromium-doped ruthenium dioxide with oxygen vacancies, termed Cr0.2Ru0.8O2-x, that drives OER with an overpotential of 170 mV at 10 mA cm−2 and operates stably over 2000 h in acidic media. Experimental and theoretical studies show that the synergy of Cr dopant and oxygen vacancy induces an unconventional dopant-mediated hydroxyl spillover mechanism. Such dynamic hydroxyl spillover from Cr dopant to Ru active site changes the rate-determining step from OOH* formation to O2 formation and thus greatly improves the OER performance. Moreover, the Cr dopant and oxygen vacancy also play a crucial role in stabilizing surface Ru and lattice oxygen in the Ru-O-Cr structural motif. When assembled into the anode of a practical PEMWE device, Cr0.2Ru0.8O2-x enables long-term durability of over 200 h at an ampere-level current density and 60 degrees centigrade.

Exploring the synergistically enhanced activity of novel α-MnSe/ppy composite for superior OER catalyst in alkaline medium

The extremely slow kinetics of the water-splitting process stymies the synthesis of hydrogen (H2) from water. To comprehend the main obstacle to the oxygen evolution reaction (OER), it is also necessary to enhance the development of efficient OER electrocatalysts. In this work, manganese selenide with polypyrrole heterostructure is synthesized, described, and electrochemically assessed as an effectiveelectrocatalystfor OER. The novel synthesized materialis characterizedusing a variety of techniques, including scanning electron microscopy (SEM), powder x-ray diffraction (PXRD), transmission electron microscopy (TEM) etc. The unique α-MnSe/ppy composite catalyst is shown to be exceedingly efficient, starting the OER at an astoundingly low voltage of 168 mV (vs. reversible hydrogen electrode [RHE]) at 10 mA cm−2, with a tafel slope of 67 mV dec-1. Also, operando UV–Vis spectro-electrochemical studies give an insight towards the intermediate species formed during the OER catalysis. Under similar electrochemical conditions, the α-MnSe/ppy electrocatalyst outperforms its α-MnSe and ppy counterparts for OER in an aqueous KOH (1.0 M) solution. These results surpass benchmark electrocatalysts made of Mn and rare earth metals. With this invention, a desired non-noble metal is made available that works excellently as an OER electrocatalyst.

Insulator-Transition-Induced Degradation of Pyrochlore Ruthenates in Electrocatalytic Oxygen Evolution and Stabilization through Doping.

Ru-based pyrochlores (e.g., Y2Ru2O7-δ) are promised to replace IrO2 in polymer electrolyte membrane (PEM) electrolyzers. It is significant to reveal the cliff attenuation on the oxygen evolution reaction (OER) performance of these pyrochlores. In this work, we monitor the structure changes and electrochemical behavior of Y2Ru2O7-δ over the OER process, and it is found that the reason of decisive OER inactivation is derived from an insulator transition occurred within Y2Ru2O7-δ due to its inner "perfecting" lattice induced by continuous atom rearrangement. Therefore, a stabilization strategy of the Ir-substituted Y2Ru2O7-δ is proposed to alleviate this undesirable behavior. The double-exchange interaction between Ru and Ir in [RuO6] and [IrO6] octahedra leads the charge redistribution with simultaneous spin configuration adjustment. The electronic state in newly formed octahedrons centered with Ru 4d3 (with the state of eg'↑↑a1g ↑ eg 0) and Ir 5d6 (eg'↑↓↑↓a1g ↑↓ eg 0) relieves the uneven electron distributions in [RuO6] orbital. The attenuated Jahn-Teller effect alleviates atom rearrangement, represented as the mitigation of insulator transition, surface reconstruction, and metal dissolution. As results, the Ir-substituted Y2Ru2O7-δ presents the greatly improved OER stability and PEM durability. This study unveils the OER degradation mechanism and stabilization strategy for material design of Ru-based OER catalysts for electrochemical applications.

In-situ growth strategy to synthesize porous nano-coral-like structure OER catalyst based on nife foam alloy substrate

The preparation of alloy-based catalysts is an effective approach to simplify the catalyst synthesis process for electrocatalysis. The oxygen evolution reaction (OER) is considered a key step in water splitting. By incorporating interface engineering design, electronic state optimization, and heteroatom doping, the electrocatalytic performance can be enhanced. In this study, a simple method was used to activate the NiFe foam (NIF) alloy substrate by acid etching, followed by in-situ S-doping of Cr via a hydrothermal method to synthesize S-Cr0.6@NiFe/NIF catalyst material. Its outstanding porous nanocoral-like structure not only provides abundant active sites but also exhibits superior catalytic water splitting performance, demonstrating superhydrophilic and superaerophobic characteristics. At a current density of 10 mA cm−2, only 262 mV overpotential is required to drive the OER (under basic conditions of 1 M KOH), with a low Tafel slope (71.6 mV dec−1) and a large electrochemical active surface area (ECSA = 85.25 cm2). After 80 hours of OER test, the current density of S-Cr0.6@NiFe/NIF shows negligible change. This study provides an attractive, effective, and feasible method for the in-situ growth design of alloy-based catalysts.

RuO2/FeCo2O4 as an efficient oxygen evolution reaction catalyst in alkaline medium

The oxygen evolution reaction (OER) is a four-electron-proton reaction requiring a large overpotential. In order to improve the electrocatalytic activity of iron-based OER electrocatalysts, the overpotential must be reduced in order to improve the efficiency and cost-effectiveness. Herein, FeCo LDH, FeCo2O4, RuO2/FeCo2O4, and Ru/CoFe LDH are synthesized on carbon cloth (CC) by a simple hydrothermal and annealing technique. The materials are characterized systematically, and their electrocatalytic OER properties are evaluated in detail. RuO2/FeCo2O4 delivers superior OER performance in 1 M KOH, such as a low onset potential 1.55 V at a current density of 10 mA/cm−2, a Tafel slope of 85.2 mV/dec−1, as well as robust stability. The Mott-Schottky analysis reveals that the built-in electric field accelerates charge transfer and enhances the catalytic activity of RuO2/FeCo2O4.

Synergistic Sr Activation and Cr Buffering Effect on RuO2 Electronic Structures for Enhancing the Acidic Oxygen Evolution Reaction.

The oxygen evolution reaction (OER) performance of ruthenium-based oxides strongly correlates with the electronic structures of Ru. However, the widely adopted monometal doping method unidirectionally regulates only the electronic structures, often failing to balance the activity and stability. Here, we propose an "elastic electron transfer" strategy to achieve bidirectional optimization of the electronic structures of Sr, Cr codoped RuO2 catalysts for acidic OER. The introduction of electron-withdrawing Sr intrinsically activates the Ru sites by increasing the oxidation state of Ru. Simultaneously, Cr acts as an electron buffer, donating electrons to Ru in the presence of Sr in the as-prepared catalysts and absorbing excess electrons from Sr leaching during the OER. Such a bidirectional regulation feature of Cr prevents overoxidation of Ru and maintains its high oxidation state during the OER. The optimal Ru3Cr1Sr0.175 catalyst exhibits a low overpotential (214 mV @ 10 mA cm-2) and excellent stability (over 300 h).

Tailoring the Compositions and Nanostructures of Trimetallic Prussian Blue Analog-Derived Carbides for Water Oxidation.

The electrochemical splitting of water for hydrogen production faces a major challenge due to its anodic oxygen evolution reaction (OER), necessitating research on the rational design and facile synthesis of OER catalysts to enhance catalytic activity and stability. This study proposes a ligand-induced MOF-on-MOF approach to fabricate various trimetallic MnFeCo-based Prussian blue analog (PBA) nanostructures. The addition of [Fe(CN)6]3- transforms them from cuboids with protruding corners (MnFeCoPBA-I) to core-shell configurations (MnFeCoPBA-II), and finally to hollow structures (MnFeCoPBA-III). After pyrolysis at 800°C, they are converted into corresponding PBA-derived carbon nanomaterials, featuring uniformly dispersed Mn2Co2C nanoparticles. A comparative analysis demonstrates that the Fe addition enhances catalytic activity, while Mn-doped materials exhibit excellent stability. Specifically, the optimized MnFeCoNC-I-800 demonstrates outstanding OER performance in 1.0mKOH solution, with an overpotential of 318mV at 10mAcm-2, maintaining stability for up to 150h. Theoretical calculations elucidate synergistic interactions between Fe dopants and the Mn2Co2C matrix, reducing barriers for oxygen intermediates and improving intrinsic OER activity. These findings offer valuable insights into the structure-morphology relationships of MOF precursors, advancing the development of highly active and stable MOF-derived OER catalysts for practical applications.

Mn(OH)2-Decorated 3D Architectures Built from Nickel Carbonate Hydroxide Nanostructured Spheres as Oxygen Evolution Reaction Catalysts

Mn(OH)₂-Decorated 3D Architectures Built from Nickel Carbonate Hydroxide Nanostructured Spheres as Oxygen Evolution Reaction Catalysts

The dual gain strategy of introducing nickel doping and anchoring amorphous iron oxyhydroxide nanosheets on ZIF-67 achieves an efficient oxygen evolution reaction

A ZIF-67@Ni@FeOOH composite material was synthesized using nickel-doped ZIF-67 as a precursor and was electrochemically characterized as an efficient oxygen evolution reaction (OER) catalyst. The results indicated that Ni doping preserved the polyhedral structure of ZIF-67 while enhancing its OER activity. The introduction of amorphous FeOOH nanosheets allowed ZIF-67@Ni@FeOOH to not only retain its original polyhedral structure but also develop a hollow interior and self-remodeling surface, resulting in numerous defects. These features contribute to improved charge transfer efficiency and enhanced conductivity of the material. The dual enhancement effect is achieved by combining the doping strategy with structural defect engineering. The synergistic effects of Co, Ni, and Fe species further boost OER performance. The ZIF-67@Ni@FeOOH catalyst exhibited remarkable OER efficacy, with the lowest overpotential at a current density of 10 mA cm−2 being 329 mV and a low Tafel slope of 42.95 mV dec−1. In situ Raman spectroscopy revealed that high-valence hydroxyl oxides, specifically NiOOH and CoOOH, present on the composite surface were the active species for OER. This study offers a promising approach for developing economically viable electrocatalysts with superior efficiency for OER.

Development of carbon dots supported on Zr-MOFs nano-composites for effective oxygen evolution reaction

Efficient hydrogen generation from water splitting is a key component of the hydrogen economy. It has been extensively researched for decades how electrochemically splitting water using electrocatalysts might provide a sustainable and environmentally friendly hydrogen energy source. Sluggish kinetics of the oxygen evolution reaction (OER) hinders the process of overall water splitting. Although metal-organic frameworks (MOFs) are attractive for generation of effective OER electrocatalysts, their activity is significantly hindered by their inherent lower conductivity. Here, we demonstrate a Zr-MOF-based composite with carbon dots (CDs) in order to increase their OER activity. Its exceptional morphology with higher porosity and greater surface area results in enhanced electrochemical activity. It reveals tremendously low onset potential, i.e., 1.40 V vs. RHE, and a remarkably small overpotential of 1.45 V vs. RHE to attain benchmark current density. It exhibited a minimal Tafel value of 37 mV/dec, conquering state-of-the-art catalysts for OER. The fabricated electrocatalyst demonstrated a lower charge transfer resistance (Rct) of 0.248 Ω, with exceptional durability for about 20 h in chronoamperometric studies and for up to 1500 CV cycles. All these results demonstrated that as-fabricated Zr-MOF-based composite is a probable and potential candidate for OER.

Plasma-Induced Oxygen Defect Engineering in Perovskite Oxide for Boosting Oxygen Evolution Reaction.

Perovskite oxides are considered highly promising candidates for oxygen evolution reaction (OER) catalysts due to their low cost and adaptable electronic structure. However, modulating the electronic structure of catalysts without altering their nanomorphology is crucial for understanding the structure-property relationship. In this study, a simple plasma bombardment strategy is developed to optimize the catalytic activity of perovskite oxides. Experimental characterization of plasma-treated LaCo0.9Fe0.1O3 (P-LCFO) reveals abundant oxygen vacancies, which expose numerous active sites. Additionally, X-ray photoelectron spectroscopy and X-ray absorption fine structure analyses indicate a low Co valence state in P-LCFO, likely due to the presence of these oxygen vacancies, which contributes to an optimized electronic structure that enhances OER performance. Consequently, P-LCFO exhibits significantly improved OER catalytic activity, with a low overpotential of 294mV at a current density of 10mAcm-2, outperforming commercial RuO2. This work underscores the benefits of plasma engineering for studying structure-property relationships and developing highly active perovskite oxide catalysts for water splitting.

Studies on Porous Nanostructured Palladium–Cobalt–Silica as Heterogeneous Catalysts for Oxygen Evolution Reaction

Studies on Porous Nanostructured Palladium–Cobalt–Silica as Heterogeneous Catalysts for Oxygen Evolution Reaction

Amorphous P-CoOX Promotes the Formation of Hypervalent Ni Species in NiFe LDHs by Amorphous/Crystalline Interfaces for Excellent Catalytic Performance of Oxygen Evolution Reaction.

Water electrolysis has become an attractive hydrogen production method. Oxygen evolution reaction (OER) is a bottleneck of water splitting as its four-electron transfer procedure presents sluggish reaction kinetics. Designing composite catalysts with high performance for efficient OER still remains a huge challenge. Here, the P-doped cobalt oxide/NiFe layered double hydroxides (P-CoOX/NiFe LDHs) composite catalysts with amorphous/crystalline interfaces are successfully prepared for OER by hydrothermal-electrodeposition combined method. The results of electrochemical characterizations, operando Raman spectra, and DFT theoretical calculations have demonstrated the electrons in the P-CoOX/NiFe LDHs heterointerfaces are easily transferred from Ni2+ to Co3+ because that the amorphous configuration of P-CoOX can well induce Ni-O-Co orbital coupling. The electron transfer of Ni2+ to the surrounding Fe3+ and Co3+ will lead to the unoccupied eg orbitals of Ni3+ that can promote water dissociation and accelerate *OOH migration to improve OER catalytic performance. The optimized P-CoOX/NiFe LDHs exhibit superior catalytic performance for OER with a very low overpotential of 265mV at 300mA cm-2 and excellent long-term stability of 500h with almost no attenuation at 100mA cm-2. This work will provide a new method to design high-performance NiFe LDHs-based catalysts for OER.