Oxygen Evolution Reaction In Alkaline Media Research Articles

Sputtering induced the architecture of “needle mushroom” shaped Cu2O–NiCo2O4 heterostructure with novel morphology and abundant interface for high-efficiency electrochemical water oxidation

Oxygen evolution reaction (OER) is widely recognized as a bottleneck in the kinetics and activity of decomposition water. Unique geometric design and compositional regulation are important technologies for achieving significant activity and excellent kinetics, but they continue to face obstacles in reaction thermodynamics and kinetic response. Here, a “needle mushroom” shaped Cu2O–NiCo2O4 heterostructure with abundant active sites and optimized conductivity that is grown on the Nickel-foam (NF) (labeled as Cu2O–NiCo2O4/NF-2) is prepared using advanced magnetron sputtering strategies for electrochemical water oxidation. Based on the excellent geometric advantages and efficient charge transfer capabilities, the catalyst of Cu2O–NiCo2O4/NF-2 shows superior electrocatalytic activity (low overpotential) and kinetics (low electrochemical impedance) compared with nanoneedle shaped Cu2O–NiCo2O4/NF-1 and NiCo2O4/NF for OER in alkaline medium. This work demonstrates a practical and economical strategy toward the fabrication of ternary transition metal oxides for water oxidation.

Exploring the Effect of Ball Milling on the Physicochemical Properties and Oxygen Evolution Reaction Activity of Nickel and Cobalt Oxides

Ball milling is commonly used to reduce catalyst particle size. However, little attention is paid to further changes that ball milling can cause to the rest of the catalysts’ physicochemical properties, which can impact their intrinsic catalytic activity. The effect of ball milling on the physicochemical properties of NiCoO2, NiO, CoO, and NiO:CoO mixtures is reported and correlated with their electrochemical oxygen evolution reaction (OER) activity. It is also shown that particle fragmentation is an inherent consequence of ball milling, but some oxides can also experience a phase transformation. In the case of rocksalt‐structured CoO, it is partially or entirely transformed to spinel‐structured Co3O4. Additionally, NiCo2O4 with a spinel structure can be formed by ball milling NiO and CoO simultaneously (both rocksalt structures), but only in the absence of water. The changes impact the electrochemical activity of the initial oxides. Ball milled NiCoO2 exhibits the highest activity with a mean potential of 1.563 V at 10 mA cm−2, demonstrating the advantage of having Ni and Co in the same structure. Although NiCo2O4 is also a binary oxide, the results indicate that its metal coordination environment makes it intrinsically less active than NiCoO2 for the OER in alkaline media.

Enhancing Iron Oxide Electrocatalysis for Efficient Overall Water Splitting: A Study of Tailored Synthesis for Advanced Energy Generation and Storage

ABSTRACTWater splitting, a critical milestone in the development of renewable energy, allows the production of pure hydrogen and oxygen. Iron oxide (Fe2O3), a fundamental component in electrochemical water splitting for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), offers potential because of its accessibility, low cost, and environmental safety. Herein, to analyze the impact of the methodology on its properties, Fe2O3 was produced in three different ways: freeze‐drying (aerogel) (Fe2O3‐AG), hydrothermal (Fe2O3‐HT), and microwave (Fe2O3‐MW). The Fe2O3‐AG outperformed Fe2O3‐HT and Fe2O3‐MW in most properties which showed improved current and overall water‐splitting efficiency. The resulting materials demonstrated good electrocatalytic performance for both HER and OER in alkaline media, with overpotentials for HER of 204, 235, and 255 mV and overpotentials for OER of 222, 288, and 292 mV for the Fe2O3‐AG, Fe2O3‐HT, and Fe2O3‐MW samples, respectively, at a current density of 10 mA/cm2. The freeze‐drying synthesis process has significant potential as a feasible method for the manufacture of Fe2O3‐based electrocatalysts for water‐splitting applications. This study provides important insights into the influence of electrocatalytic and energy storage properties of Fe2O3 based on the use of different methodologies, that is, hydrothermal, microwave‐assisted, and freeze‐drying. Through that, a more assertive analysis can be made concerning changes in morphology, conductivity, exposure of active area, and electrochemical stability which are crucial for the overall performance, hence providing valuable information and considerations for possible large‐scale applications for energy generation and energy storage.

Ionic liquid-assisted controlled synthesis of multi-site Ni2P as a bifunctional catalyst for electrocatalytic water splitting

It is crucial to develop effective electrocatalysts with multiple active sites for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in order to promote the advance energy conversion and development of sustainable energy technology. Here, we synthesized hierarchical nanostructured Ni2P on carbon cloth using ionic liquid (IL) assisted sacrificial template strategy through a simple two-step hydrothermal phosphatization process, which served as an electrode for enhancing bifunctional water electrolysis. By changing the content of ionic liquids in the solvent, the morphology of Ni(OH)2 precursors could be regulated, thereby altering the morphology of Ni2P. Ni2P exhibited remarkable electrocatalytic activity towards HER in acidic electrolytes with an overpotential of 132 mV at a current density of 10 mA cm−2, as well as OER in alkaline media with the overpotential of 309 mV. The excellent electrocatalytic activity of the Ni2P-2 could be attributed to its hierarchical nanostructure providing abundant active sites, which benefits from the structural end-capping effect of ILs.

Lycium ruthenicum stem extract mediated green synthesis of MnO2/Mn3(PO4)2 composite nanowire electrocatalyst for oxygen evolution reaction

A composite of manganese oxide (MnO2) and Mn3(PO4)2 decorated nanowires (MnO2/Mn3(PO4)2) was prepared using Lycium ruthenicum stem-extract mediated green synthesis. This composite material functions as an efficient and long-lasting electrocatalyst for water-splitting reactions, which could significantly improve the performance of oxygen evolution reaction (OER). The OER activity of MnO2/Mn3(PO4)2-based nanowires is boosted by blending with a conducting support, such as manganese oxide (MnO2). The x-ray diffraction pattern and Fourier transform infrared data indicate that the nanowires are highly crystalline. The MnO2/Mn3(PO4)2 composite material demonstrates superior stability compared to its individual constituents and generates a current density of 10 mA cm−2 at a low overpotential of 244 mV for OER in alkaline media. This research may lead to the development of MnO2/Mn3(PO4)2 composite materials as electrocatalysts for overall water-splitting reactions.

Zr and Mo doping to modulate the electronic structure of Ni3S2 for OER electrocatalysis

To enter the era of a clean and sustainable hydrogen economy, it is crucial to first discover non-precious metal electrocatalysts that can be used for oxygen evolution reaction (OER) in electrochemical water splitting. In this work, highly active and durable Zr and Mo co-doped Ni3S2 catalyst (ZrMo–Ni3S2/NF) loaded on Ni foams for OER in alkaline media were prepared using a simple one-step hydrothermal method. The resulting nanocomposites were characterized by various methods and evaluated for their electrocatalytic performance towards OER. The ZrMo–Ni3S2/NF nanocomposite exhibites excellent OER electrocatalytic activity with a low overpotential of 257 mV at a current density of 10 mA cm−2 as well as an excellent electrochemical stability, showing only a slight decay during the 70 h test period. The remarkable electrocatalytic performance of the ZrMo–Ni3S2/NF electrode is attributed to the synergistic strong electronic interaction between the co-doped Zr and Mo. This work not only demonstrates a highly electrocatalytic active OER catalyst for water splitting, but also provides a new perspective on the development of highly active OER catalysts through doping strategies.

A one-pot hydrothermal synthesis of morphologically controllable yolk-shell structured CoFe glycerate spheres for oxygen evolution reaction

CoFe-based catalysts are efficient electrocatalysts for the oxygen evolution reaction (OER) in alkaline media. Here, we present a simple one-pot hydrothermal method for synthesizing a series of CoFe glycerates with controllable surface morphologies and investigate their potential as highly efficient catalysts for the OER in alkaline media. These CoFe glycerates exhibit a unique yolk-shell microsphere structure assembled from ultrathin nanosheets. The adjustment of the surface nanosheet size is achieved by varying the CoFe ratio, ensuring a more efficient electrocatalytic system for the OER process. Due to the abundant active sites provided by the yolk-shell structure and interleaved ultrathin nanosheets, Co3Fe1 glycerate (Co3Fe1 gly) demonstrates a low overpotential (283 mV) and a small Tafel slope (44.61 mV dec−1) at 10 mA cm−2. Additionally, Co3Fe1 gly exhibits excellent durability in alkaline electrolytes. Moreover, a series of characterizations demonstrate that the active sites of Co3Fe1 gly are the high-valence Co species generated during the OER process. This study opens a promising avenue for utilizing efficient and low-cost electrocatalysts to enhance OER performance.

Improvement in electrochemical performance of SrTiO3 with rGO via composite (SrTiO3/rGO) strategy fabricated via solvothermal approach

Developing sustainable and highly effective electrocatalysts for the oxygen evolution reaction (OER) is a significant research target for precise custody of water splitting to fulfill worldwide energy demands. This study focuses on the fabrication of SrTiO3/rGO-based composite via a solvothermal technique, which works as an electrocatalyst for evaluating the efficiency of OER in alkaline media. The material displays outstanding OER efficacy in 1 M KOH solution with its cubic structure validated by the X-ray diffraction (XRD) study. The electrochemical study reveals that the SrTiO3/rGO composite has a minimal overpotential (222 mV) compared to SrTiO3 (289 mV) and the commercial catalyst RuO2 (367 mV). The SrTiO3/rGO composite also has a minimal Tafel plot gradient of 37 mV dec−1 whereas RuO2 has a Tafel value of 72 mV dec−1. The current material has superior properties compared to RuO2, a commercial catalyst for the OER. The SrTiO3/rGO composite shows exceptional stability for 40 h. The low conductivity of oxygen-deficient SrTiO3 perovskite can be improved by incorporating carbon-based rGO into it, as demonstrated by the minimal Rct (0.07 Ω) obtained from electrochemical impedance spectroscopy (EIS) analysis and an enlarged surface area of 250 cm2, as evidenced by electrochemical surface area (ECSA). Therefore, our research indicates that a particular morphology of metal oxide can improve the efficiency of electrocatalysis when combined with reduced graphene oxide (rGO), suggesting its potential for generating effective and environmentally friendly energy. Hence, these findings may improve the smooth passage of electrons and provide a novel perspective to function as an adequate substitute for RuO2, a commercial catalyst.

Oxygen vacancy-engineered P-doped MoO3/Ce2Mo4O15 bimetallic heterojunction nanosheet array for enhanced oxygen evolution reaction

Surface oxygen vacancies in defective metals have the capacity to enhance oxygen evolution reaction (OER) activity but easily suffer from instability and deactivation in continuous electrocatalysts. Heterojunction engineering is important for achieving effective catalysis, but its simultaneous engineering remains a challenge. Therefore, it is necessary to develop an effective heterojunction catalyst to improve the electrocatalytic stability of defective metallic oxygen vacancies. In this work, we report a Ce, Mo bimetallic defective heterojunction P-MoO3/Ce2Mo4O15@NF-1 via a facile one-step hydrothermal method and annealing in a tube furnace. Bimetallic oxide heterojunctions offer several advantages over conventional single-metal heterojunctions, including stable structure, more active sites, faster rates of electron transfer, and less pollution of the environment. Meanwhile, P-doped catalyst could enhance the metallicity significantly. In addition, the prepared catalyst P-MoO3/Ce2Mo4O15@NF-1 showed extraordinary catalytic activity for OER in alkaline media. The overpotential and Tafel slope of the catalyst at a current density of 50 mA cm-2 were 270 mV and 87.27 mV dec‑1, respectively. It maintains an impressive balance between electrocatalytic activity and stability. This research explores the co-effects of Ce and Mo bimetallic oxide in defective electrocatalysts and also provides ideas for designing OER catalysts with defective metal heterojunctions.

Multiwall carbon nanotubes supported rhenium doped Co3O4 as an efficient electrocatalyst for water oxidation in alkaline medium

The recent trends for the development of efficient and low cost transition metal (TMs) based anode catalysts for water splitting is crucial and important. Even though, research is continuously progressing in different directions to design catalyst; however, catalytic OER (oxygen evolution reaction) activity has remained insufficient. Till now, various transition metal oxides (TMOs) have been used as efficient and cost-effective electrocatalyst for the oxygen evolution reaction. The catalytic performance of TMOs could be enhanced by doping with the metal, which increases the catalyst's charge transfer and electronic conductivity. Decoration of TMOs with the multi-wall carbon nanotube (MWCNT) further improves catalytic activity by providing numerous active sites. Here, Co3O4/MWCNT and Rhenium (Re) doped Co3O4/MWCNT composite were prepared by simple hydrothermal process and used as electrocatalyst for OER in alkaline medium. Different concentrations of Re (0.05 mmol, 0.1 mmol, 0.2 mmol, 0.3 mmol) were doped and it was observed that the electrochemical results of the 0.2 mmol Re doped Co3O4/ MWCNT (R0.2CO) was most efficient electrocatalyst which offers the OER overpotential of 298 mV/dec to attain the 10 mA cm−2 current density, lower Tafel slope (70 mV/dec), higher value of turn over frequency (0.95), lower value of the charge transfer resistance (3.10Ω) and good stability, demonstrating the better OER catalytic activity as compared to un-doped Co3O4/MWCNT (R0.0CO) catalyst. The investigated catalyst R0.2CO is more efficient catalyst than most of the reported similar type of catalysts and offers comparable electrocatalytic activity with benchmark electrocatalyst RuO2.

Construction of heterogeneous interfaces for water activation and dissociation to synergistically boost overall water splitting

Construction of heterogeneous interfaces with dual active components to synergistically promote both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is an effective strategy for facilitating electrochemical water splitting, but the appropriate active component regulation via simple synthesis procedures is still challenging. Herein, the Co and Co2Mo3O8 active components are screened to construct effective heterogeneous interfaces and successfully integrated on Ni foam by thermal reduction of cobalt molybdate precursor. And this bifunctional electrode (Co/Co2Mo3O8/NF) required overpotentials of only 164 and 360 mV to drive the 100 mA cm−2 for HER and OER in alkaline media, respectively. Theoretical calculations showed that the electron transfer occurred from Co to Co2Mo3O8 at the interface, then the formed interfacial cobalt atoms with deficient electron were beneficial for water activation, and reduced energy barrier of water dissociation under the synergistic effect of Co2Mo3O8. Notably, the alkaline electrolyzer based on symmetric Co/Co2Mo3O8/NF electrodes generated 100 mA cm−2 at a voltage of only 1.75 V, surpassing commercially available precious-metal Pt/RuO2-based catalysts.

Room‐Temperature, Meter‐Scale Synthesis of Heazlewoodite‐Based Nanoarray Electrodes for Alkaline Water Electrolysis

AbstractAlkaline water electrolysis is among the most promising technologies to massively produce green hydrogen. Developing highly‐active and durable electrodes to catalyze the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) is of primary importance. Here a facile, room‐temperature synthetic route is presented to access heazlewoodite phase (Ni, Fe)3S2 nanosheet arrays supported on NiFe foam (NFF), whose production can be easily scaled up to meter size per batch operation. The (Ni, Fe)3S2/NFF electrode can serve as a high‐performance electrocatalyst for both HER and OER in alkaline media, and remains highly stable for over 1000 h at 100 mA cm−2 current densities. When working as HER electrocatalyst, (Ni, Fe)3S2 is confirmed as catalytic phase that provides a high density of efficient active sites (e.g., Ni─Ni and Ni─Fe bridge sites). During electrochemical OER testing, (Ni, Fe)3S2 nanosheets totally transform into γ‐(Fe, Ni)OOH as active catalytic phase for OER. As a consequence, the (Ni, Fe)3S2/NFF can be used to integrate into an alkaline electrolyzer as both the cathode and anode, and to give an excellent catalytic performance (600 mA cm−2 @1.93 V), which is better than the alkaline electrolyzer based on commercial Raney Ni electrodes.

Ru nanoparticles modified Ni3Se4/Ni(OH)2 heterostructure nanosheets: A fast kinetics boosted bifunctional overall water splitting electrocatalyst

Properly design and manufacture of bifunctional electrocatalysts with superb performance and endurance are crucial for overall water splitting. The interfacial engineering strategy is acknowledged as a promising approach to enhance catalytic performance of overall water splitting catalysts. Herein, the Ru nanoparticles modified Ni3Se4/Ni(OH)2 heterostructured nanosheets catalyst was constructed using a simple two-step hydrothermal process. The experimental results demonstrate that the abundant heterointerfaces between Ru and Ni3Se4/Ni(OH)2 can increase the number of active sites and effectively regulate the electronic structure, greatly accelerating the kinetics of the hydrogen evolution reaction (HER)/oxygen evolution reaction (OER). As a result, the Ru/Ni3Se4/Ni(OH)2/NF catalyst exhibits the low overpotential of 102.8 mV and 334.5 mV at 100 mA cm−2 for HER and OER in alkaline medium, respectively. Furthermore, a two-electrode system composed of the Ru/Ni3Se4/Ni(OH)2/NF requires a battery voltage of just 1.51 V at 10 mA cm−2 and remains stable for 200 h at 500 mA cm−2. This work provides an effective strategy for constructing Ru-based heterostructured catalysts with excellent catalytic activity.

The oxygen path mechanism from Ni-OOOO-Fe species in oxygen evolution reaction on NiFe layered double hydroxides

The oxygen evolution reaction (OER) with large overpotential is the bottleneck of the whole water electrolysis process. NiFe layered double hydroxide (NiFe-LDH) represent one of the potential catalysts for OER in alkaline media. For the LDH, it was well established that both adsorption evolution mechanism and lattice oxygen mechanism could appear at a single site, but Ni-OOOO-Fe species would provide a different OO path mechanism at dual-O sites due to the complexity and diversity of LDH surface. Here, using first-principles study, tetra-oxygen path mechanism (t-OPM) was proposed to investigate the OER performance of NiFe-LDH by considering surface 2O were as active sites (Oac) and other O as environment O (Oev) with different exposed degrees (0–6). It was found that the optimal performance of the NiFe-LDH surface could be achieved when 2 ∼ 4 Oev were exposed under the explored mechanism in different paths (path 1 and path 2) with overpotential η = 0.07 ∼ 0.35 V, and path 1 was slightly better than path 2. At the same time, the solvation effect (SE) was used to study the effect on the OER performance, the results showed that SE had a little influence on the case of 2 ∼ 4 Oev exposed while had a large effect on the other cases. The detailed analysis of the electronic structure showed a smaller difference Δε between the energy Fe-3d band center and Oac-2p, which imply the stronger the interaction between them. Thus, the t-OPM was feasible in OER on NiFe-LDH. It was anticipated that our work could provide a fresh perspective on the understanding of the excellent OER performance of LDH in alkaline environment, which was complementary to the traditional mechanism to some extent.

Boosting oxygen evolution reaction rates with mesoporous Fe-doped MoCo-phosphide nanosheets.

Transition metal-based catalysts are commonly used for water electrolysis and cost-effective hydrogen fuel production due to their exceptional electrochemical performance, particularly in enhancing the efficiency of the oxygen evolution reaction (OER) at the anode. In this study, a novel approach was developed for the preparation of catalysts with abundant active sites and defects. The MoCoFe-phosphide catalyst nanosheets were synthesized using a simple one-step hydrothermal reaction and chemical vapor deposition-based phosphorization. The resulting MoCoFe-phosphide catalyst nanosheets displayed excellent electrical conductivity and a high number of electrochemically active sites, leading to high electrocatalytic activities and efficient kinetics for the OER. The MoCoFe-phosphide catalyst nanosheets demonstrated remarkable catalytic activity, achieving a low overpotential of only 250 mV to achieve the OER at a current density of 10 mA cm-2. The catalyst also exhibited a low Tafel slope of 43.38 mV dec-1 and maintained high stability for OER in alkaline media, surpassing the performance of most other transition metal-based electrocatalysts. The outstanding OER performance can be attributed to the effects of Mo and Fe, which modulate the electronic properties and structures of CoP. The results showed a surface with abundant defects and active sites with a higher proportion of Co2+ active sites, a larger specific surface area, and improved interfacial charge transfer. X-ray photoelectron spectroscopy (XPS) analysis revealed that the catalyst's high activity originates from the presence of Mo6+/Mo4+ and Co2+/Co3+ redox couples, as well as the formation of active metal (oxy)hydroxide species on its surface.

N/P-doped NiFeV oxide nanosheets with oxygen vacancies as an efficient electrocatalyst for the oxygen evolution reaction.

Plasma treatment as an effective strategy can simultaneously achieve surface modification and heteroatom doping. Here, an N/P-doped NiFeV oxide nanosheet catalyst (N/P-NiFeVO) constructed by Ar/PH3 plasma treatment is used to drive the oxygen evolution reaction (OER). The introduction of V species leads to the formation of an ultrathin ordered nanostructure and exposure of more active sites. Compared to the 2D NiFeV LDH, the prepared N/P-NiFeVO by plasma treatment possesses multiple-valence Fe, V and Ni species, which regulate the intrinsic electronic structure and enable a superior catalytic activity for the OER in alkaline media. Specifically, the N/P-NiFeVO only require an overpotential of 273 mV to drive the current density of 100 mA cm-2. What's more, the electrode can maintain a stable current density in a long-term oxygen evolution reaction (∼120 h) under alkaline conditions. This work provides new insight for the rational design of mixed metal oxides for OER electrocatalysts.

Transition metal-based electrocatalysts for alkaline overall water splitting: advancements, challenges, and perspectives.

Water electrolysis is a promising method for efficiently producing hydrogen and oxygen, crucial for renewable energy conversion and fuel cell technologies. The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are two key electrocatalytic reactions occurring during water splitting, necessitating the development of active, stable, and low-cost electrocatalysts. Transition metal (TM)-based electrocatalysts, spanning noble metals and TM oxides, phosphides, nitrides, carbides, borides, chalcogenides, and dichalcogenides, have garnered significant attention due to their outstanding characteristics, including high electronic conductivity, tunable valence electron configuration, high stability, and cost-effectiveness. This timely review discusses developments in TM-based electrocatalysts for the HER and OER in alkaline media in the last 10 years, revealing that the exposure of more accessible surface-active sites, specific electronic effects, and string effects are essential for the development of efficient electrocatalysts towards electrochemical water splitting application. This comprehensive review serves as a guide for designing and constructing state-of-the-art, high-performance bifunctional electrocatalysts based on TMs, particularly for applications in water splitting.

Cobalt–organic framework as a Bi–functional electrocatalyst for renewable hydrogen production by electrochemical water splitting

Sustainable hydrogen production by electrocatalytic water splitting is an attractive approach to establish a carbon–free future. On the other hand, the operationalization of this technology on a large scale requires the design and synthesis of efficient electrocatalysts to promote hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Metal–organic frameworks (MOFs) have provided new opportunities in the field of electrocatalytic water splitting due to their unique properties. Herein, we report an affordable, simple, and environmentally friendly strategy for the synthesis of Co3(BTC)2 MOF electrocatalyst in distilled water at room temperature. Surprisingly, Co3(BTC)2 demonstrated superior electrocatalytic activity toward HER and OER in alkaline media. The Co3(BTC)2 requires overpotentials of 450 and 370mV for HER and OER to achieve a current density of 10mA cm−2, respectively.

NiFe codoping-regulated amorphous/crystalline heterostructured Co-based hydroxides/tungstate with rich oxygen vacancies for efficient water oxidation catalysis

Oxygen evolution reaction (OER) is a crucial half-reaction in water splitting, generating hydrogen for sustainable development, but it is often subject to sluggish kinetics. Abundant transition metal-based OER electrocatalysts have been utilized to expedite the process. However, traditional amorphous catalysts suffer from low conductivity, while the activity of crystalline catalysts is also unsatisfactory. Herein, an amorphous/crystalline heterostructured Co-based hydroxide/tungstate was meticulously constructed and further tailored using a NiFe codoping method (NiFeCoW). Following NiFe codoping, the electronic structure had been modulated, subsequently altering the adsorption toward intermediates. From the electrochemical measurements, the NiFeCoW catalyst demonstrated superior electrocatalytic activity for OER in alkaline media, with a minimal overpotential of 297 mV at 10 mA cm−2 and a cell voltage of 1.57 V for water splitting. This study provides valuable guidance for regulating the amorphous/crystalline heterophase in catalysts through bimetallic modulating engineering.

Insights into the Structure Sensitivity of Fe-Based Materials for the Oxygen Evolution Reaction

The conversion of renewable energy into storable fuels is fundamental to the meeting of the net-zero CO2 emissions objective by 2050. However, the sluggish kinetics of the oxygen evolution reaction (OER) and the poor stability of electrocatalysts at industrial-level currents remain a problem for electrolyzers 1. Using platinum group metal-free electrocatalysts in anion exchange membrane electrolyzers is an appealing strategy to overcome some of the problems associated with PEM electrolyzers. Fe-based materials offer the possibility for the development of active, stable, and cost-effective electrocatalysts for the OER in alkaline media.In this work, we explore the influence of structure, composition, or crystalline phase on different Fe-based electrodes for the OER. Different fabrication procedures such as additive manufacturing 2, flame spray synthesis, or pulse laser ablation 3 allow us to have a wide range of Fe-based materials with a well-defined structure/composition/phase. The materials have been extensively characterized by physicochemical methods (XPS, Raman, XRD, ICP) and their electrocatalytic activity evaluates following careful procedures in order to obtain reliable results. The results show that the activity of Fe-rich electrodes is poor. However, if Fe is alloyed with other materials or its surface structure or crystallinity degree is modified, it results in a more active material. This information could guide the synthesis of more active and stable water-splitting materials. References S. Cherevko, S. Geiger, O. Kasian, N. Kulyk, J.-P. Grote, A. Savan, B. R. Shrestha, S. Merzlikin, B. Breitbach, A. Ludwig, and K. J. J. Mayrhofer, Catalysis Today, 262 170-180 (2016). J. Wegner, R. Martínez-Hincapié, V. Čolić, and S. Kleszczynski, Advanced Materials Interfaces, n/a (n/a), 2202499 (2023). J. Johny, Y. Li, M. Kamp, O. Prymak, S.-X. Liang, T. Krekeler, M. Ritter, L. Kienle, C. Rehbock, S. Barcikowski, and S. Reichenberger, Nano Research, 15 (6), 4807-4819 (2022).