Ni Oxyhydroxides Research Articles

Active Sites of 3d Transition Metal Oxyhydroxides for OER

3d transitional metal oxyhydroxides, such as Ni and Co oxyhydroxides with Fe doping, are among the most active and most studied OER catalysts in alkaline electrolytes. They are also the catalysts of choice for industrial alkaline water electrolysis. Despite decades of research, the atomic-scale structures of these materials, particularly key Ni (oxy)hydroxide hosts, remain elusive. This presentation aims to fill this critical knowledge gap by combining rigorous Density Functional Theory calculations with in situ Wide Angle X-ray Scattering techniques under quasi-steady state electrochemical cycling conditions. This unique combination has enabled us to unveil the in-situ structures and (ir)reversible transformations of pure undoped Ni (oxy)hydroxides. Such an advance consequently allows us to transcend the limitations of previous modeling based on approximated structures. Specifically, based on the newly identified actual in-situ structures, we discover the existence of a previously unknown synergy at the reaction centers, coupled with the polaron effects, in promoting the oxygen evolution reaction. Such a finding sheds light on the catalytic active sites and oxygen evolution reaction pathways, particularly the exceptional activity of multiple Fe reaction centers on Ni oxyhydroxides. In addition, we found that such a phenomenon is general and also exists on NiM and CoM layered double hydroxides,1, 2 A2B2O7 pyrochlores,3 layered Co oxyhydroxides intercalated with phenanthroline through non-covalent ligand-oxide interaction.4

Incorporation of Trace Metals through in situ Cation Exchange Reactions: Electrochemical and Structural Effects on Nickel Oxyhydroxide Electrocatalysts

Understanding how electrocatalysts evolve during operation is critical to optimizing their performance. The oxygen evolution reaction (OER) exposes electrocatalytic materials to harsh conditions that lead to significant transformations. A discovery that revolutionized OER catalysis was the dramatic improvement in activity due to the intentional, or incidental, in situ incorporation of Fe into Ni and Co oxyhydroxides. This finding raised questions about the true active phase in OER catalysts. While Fe incorporation is now widely acknowledged, there is still significant room for improvement in comprehending the in situ incorporation of trace metals and its effects on the electrochemical and structural properties of transition metal oxyhydroxides.We report a comprehensive investigation of in situ metal incorporation on nickel oxyhydroxide OER electrocatalysts encompassing four multivalent cations: Fe, Co, Mn, and Cu. We found that adding trace amounts of these to alkaline electrolytes alters the electrocatalytic and energy storage properties of NiOxHy films. As opposed to the well-known increase in OER activity induced by Fe incorporation (Figure 1a), in situ incorporation of trace Co and Mn increases the redox capacitance (Figure 1b), while Cu incorporation does not proceed. Depth profiling measurements reveal that metal incorporation is confined to the film's surface (Figure 1c-d), resulting in an interstratified structure that partially retains the more active, disordered phase. We describe four factors determining the occurrence of in situ metal incorporation, underscoring its nature as a cation exchange reaction. Finally, Fe and Co cation exchange processes are manipulated by shifting the solubility equilibrium and through ion complexation. By providing a better understanding of in situ metal incorporation processes, our results underscore its potential as a strategy for manipulating the surface chemical composition. Figure 1

Compound database for gaseous metal hydroxides and oxyhydroxides

In this study computational methods are used to derive thermochemical data for Sc, Fe, Co, Ni, and Hf hydroxides and oxyhydroxides. As done previously, molecular geometries and vibrational modes were derived with DFT methods; for the enthalpies of formation more computationally intensive coupled cluster methods were necessary. For each species ΔfHo(298), So(298), and Cp in the form A + BT + CT2 + D/T + E/T2 with A, B, C, D, and E fitted constants are presented. These are combined with previously reported calculations for Al, Cr, Si, Ta, Al, Zr, Y, Yb, Gd, and Mn to build a compound database for metal hydroxides and oxyhydroxides. Sample calculations for applications where high temperature water vapor is encountered are shown. The majority of the database was generated from ab initio calculations; however, experiments were critical benchmarks for many of the species.

In-situ construction of amorphous–crystalline NiCo bimetallic oxyhydroxide for low-temperature supercapacitor device

As rechargeable energy storage device, supercapacitor (SC) cell is facing a new challenge for low-temperature application since the low-temperature environment seriously suppresses the reaction kinetics of the electrode materials. In this work, NiCo bimetallic oxyhydroxides (NixCoyOOH, Ni/Co = x/y) composed of amorphous-crystal structure were in-situ synthesized using electrodeposition, which are capable of operating at temperatures as low as − 4 °C, totally different from the pure Ni or Co oxyhydroxides counterparts. The microstructures of the NixCoyOOH were characterized by XRD, SEM, TEM, and XPS, finding an obviously transit from microparticles (NiOOH) and porous arrays (CoOOH) to flower-like nanospheres and a complicated amorphous-nanocrystalline structure. Electrochemical tests show that the Ni2Co1OOH cathode presents a super-high specific capacitance of 3720 and 2311F g−1 at low and high charging current densities of 1 and 20 A/g at 23 ℃ in aqueous electrolyte, respectively. The assembled device of Ni2Co1OOH//activated carbon (AC) delivers a high energy density of 22.8 Wh kg−1 at 7466 W kg−1 in polyvinyl alcohol (PVA)-KOH hydrogel at 0 ℃, and offers anexceptionalstability of 92.5 % of capacity after 8000 cycles at 10 A/g and 0 ℃. To evaluate the serviceability of the as-prepared electrode materials, the devices in parallel and series connections encapsulated by 3D printing exhibits a stable discharging performance at 0 °C, demonstrating a potential application in cold environment. Heteroatomic intercalating promotes the co-adsorption of hydroxyls on the double active sites of the Ni and Co, resulting in an improved supercapacitance.

Fundamental Insights into Reaction Centers and Catalytic Mechanisms of Ni- and Co-Based Layered Oxyhydroxides for the Oxygen Evolution Reaction

Water splitting to generate green H2 fuel and O2 is essential for global CO2 reductions toward net-zero emissions. In this process, however, O2 generation at the anode through the oxygen evolution reaction (OER) is inherently slower by orders of magnitude than H2 generation at the cathode. Thus, improving OER efficiency has been a major effort in electrolysis. Ni-based and Co-based layered hydroxides are among the most active and studied non-previous catalysts in alkaline electrolytes. Although tremendous advances have been made toward improving the activity and the stability of the catalysts over the past decade, there is still a lack of fundamental insights into active sites and reaction mechanisms, which has hindered the establishment of structure-property relationships.This talk will first provide fundamental insights into reaction centers and catalytic mechanisms of classic Ni oxyhydroxides and Co oxyhydroxides with and without ligand intercalation. We will further discuss the multiple-site synergy in Ni- and Co-based layered double hydroxides (LDH) and ternary hydroxides. We will show that the OER proceeds via a Mars van Krevelen mechanism, starting with the oxidation of bridge OH at the reaction centers with dual metal sites, i.e., M1-OH-M2. We will demonstrate that, to approach the minimum overpotential dictated by a specific OH-OOH scaling relationship, the key is to break the OH-O scaling relationship. A possible route is to form binary metal oxyhydroxides with dual metal sites at the reaction centers or introduce a third element into NiFe LDH or CoFe LDH. If time permits, We will further discuss the role of the non-covalent interaction and polaron-like electronic states in promoting OER at M1-OH-M2 centers.

Novel electrodeposited NiFeP/Zn bifunctional catalytic coating for alkaline water splitting

The shift towards renewable energies has promoted research into electrolysis for the obtention of pure hydrogen since this is a promising energy vector. However, electrolysis is limited due to its low efficiency. In this work, a novel NiFeP/Zn coating electrodeposited on AISI 304 steel is proposed as a bifunctional catalytic electrode for electrochemical water splitting. The leaching of Zn from the coating allows the formation of a diversified surface morphology of the electrode, obtaining an active area 1164 times greater than that of a NiFeP coating. The leaching process also allows the formation of Ni oxides, hydroxides and oxyhydroxides, which are beneficial catalytic compounds for the reactions of interest. XRD characterization indicates the presence of an amorphous structure of the coating due to the presence of P, which provides better catalytic performance for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), as well as better corrosion behavior of the electrodes. The electrocatalytic performance of the coating shows overpotentials of 163 mV for HER, and 262 mV for OER in 1 M NaOH at |10| mAcm−2. The full cell test using the NiFeP/Zn coating as bifunctional electrode shows a remarkably low overpotential equal to 1.65 V at 10 mA cm−2 for overall water splitting.

Efficient Oxygen Evolution Reaction Catalyzed by Ni/NiO Nanoparticles Produced by Pulsed Laser Ablation in Liquid Environment

Electrochemical water‐splitting, sustained by renewable energy, is aimed at green H2 production. Efficient and sustainable electrocatalysts are required for a proper energy transition. Oxygen evolution reaction (OER) in alkaline electrolyte can be pursued by using earth‐abundant elements‐based catalysts, such as Ni oxyhydroxides. A proper optimization of intrinsic properties and synthesis procedure is still needed. Herein, the synthesis of Ni/NiO nanoparticles (NPs) through a physical and green technique, pulsed laser ablation in liquid (PLAL), is presented. Ablating a Ni target in deionized water, at different ablation times, leads to NP dispersions used for realization of OER electrode onto graphene paper. Ion‐beam analysis of catalysts amount and homogeneity of NP‐based electrode is performed for the electrode optimization in terms of electrochemical performances. An overpotential at 10 mA cm−2 of 306 mV is achieved for 40 μg cm−2 of catalyst, while lowering the catalyst amount to 8 μg cm−2, unprecedented turnover frequency of 0.20 s−1 and mass activity of ≈1.3 A mg−1 are reached. These data show that Ni/NiO NPs produced by PLAL are highly effective for OER in alkaline media and encourage the use of PLAL as a green and efficient technique for electrocatalyst production.

Electronic Structure Modulation of Sulfur-Retaining Nickel-Based Electrocatalyst to Improve the Oxygen Evolution Reaction

Water electrolysis is considered as a key energy source to produce hydrogen for achieving a clean and sustainable society. Improving the sluggish kinetics of the oxygen evolution reaction (OER) is focused to overcome the limit efficiency of water electrolysis. Transition metals, especially Ni, are one of the most promising materials for the alkaline OER because of good catalytic activities, stabilities and cost efficiency. Ni based materials, such as Ni oxyhydroxides, hydroxides, phosphides and sulfides, are intensively developed for use as OER catalysts. Recently, the sulfurization of transition metals is introduced as an effective method to improve the intrinsic electrocatalytic activities. The role of S has been summarized in 2 ways. S accelerates the regeneration of transition metals in alkaline media that S is dissolved and exchanged with O species. Mullins et al. reported Nickel oxide derived from Ni-S. It exhibits amorphous and large active surface morphology which is favorable OER. The other role is that remaining S modulates the electronic structures of Ni catalysts reducing the energy barrier for the OER. Wu et al. developed ultrathin Fe-doped Ni3S2 for overall water splitting. Based on density functional theory calculations, the Fe-doped Ni3S2 surface exhibits an optimized energy for water adsorption and dissociation, which enhances the intrinsic activity for the OER. However, in-situ/operando experimental studies regarding the effects of residual S are rare.Herein, we report the role of the remaining S in Ni catalysts that exhibit longer Ni-O bonding in the NiOOH phase produced in-situ. C-supported Fe- and Co-doped nickel sulfide catalysts (NiFeCo-S/C) is prepared using a simple impregnation method with heating under an H2S atmosphere. We tested the electrochemical properties of the NiFeCo-S/C in alkaline media of 1 M KOH. It achieved current density of 10 mA cm-2 with only overpotential of 267.2 mV. Also, it maintained the OER activities for 24 h at current densities of 10 and 50 mA cm-2, respectively. Moreover, the prepared catalyst was analyzed the change of electronic structure and bonding group using in-situ/operando X-ray absorption spectroscopy (XAFS) and surface-enhanced Raman spectroscopy (SERS) under OER condition. Based on these results, we could elucidate the effects of the remaining S during the OER. Figure 1

Enhanced oxygen evolution catalyzed by in situ formed Fe-doped Ni oxyhydroxides in carbon nanotubes

In this work, rod-like NiOF-1 is synthesized and converted into hollow NiOF-1-Fe with etching effect. After pyrolysis, FeNi3 particles within in situ formed carbon nanotubes on hollow carbon nanorods are proposed as an efficient OER electrocatalyst.

Catalytic oxidation and deionization of nitrite and nitrate ions using mesoporous carbon-supported nano-flaky cobalt and nickel oxyhydroxides

The composite electrode of NiCo oxide supported by porous carbon was synthesized for nitrite oxidation and nitrate electro-sorption. The crystal structure and chemical state of the Co and Ni oxyhydroxides which were precipitated on loofah-derived activated carbon (AC) using hypochlorite were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and BET surface area. The voltammetry showed that the redox couple of Co(II)/Co(III) and Ni(II)/Ni(III) as the mediator catalytically transferred the electrons of NO2–/NO3–; the Ni site had a relatively high transfer coefficient and diffusive current, while the Co site was better in the capacitive removal of the nitrite and nitrate compounds. A batch electrolysis of nitrite ions was operated under constant anodic potential mode (0 to + 1.5 V vs. Ag/AgCl) to assess the performance of the composite electrodes. The adsorption capacity of NiCo/AC (Ni = 5% and Co = 5% on AC by weight) was 23.5 mg-N g−1, which was twice that of AC substrate (7.5 mg-N g−1), based on a multilayer adsorption model. The steady-state kinetics of the consecutive reaction were derived to determine the rate steps of the electrochemical oxidation of NO2– and adsorption of NO3–.

Structure and Oxygen Evolution Activity of β-NiOOH: Where Are the Protons?

Ni oxides and oxyhydroxides (NiOx) have been studied for a long time as cathode materials for alkaline batteries and electrocatalysts for the oxygen evolution reaction (OER). Yet, understanding of the connection between their atomic and electronic structures and electrochemical performance or stability is still incomplete. In this work, we use first-principles density functional theory (DFT) calculations to revisit the structure, electronic properties, and OER activity of β-NiOOH, the catalytically active phase of NiOx. Following extensive DFT-based screening, we identify a hitherto overlooked structure characterized by a uniform distribution of H atoms on the NiO2 layers. All the Ni3+ cations in this structure exhibit an identical tg6eg1 electronic configuration with an occupied 3dz2 orbital. Comparison of the calculated bond lengths with extended X-ray absorption fine structure (EXAFS) data unequivocally supports this structure relative to all other low-energy configurations. Based on this structure, we uncover and detail defect-dominated OER mechanisms on the basal β-NiOOH (001) surface, with overpotentials as low as 0.39 V. The present results should provide a valuable contribution to ongoing efforts for understanding and developing enhanced transition-metal hydroxide catalysts for the OER.

Iron-Facilitated Transformation of Mesoporous Spinel Nanosheets into Oxyhydroxide Active Species in the Oxygen Evolution Reaction

The oxygen evolution reaction (OER) is critical for many clean energy conversion and storage technologies because it contributes the electrons required for converting renewable electricity into value-added chemicals. Electrocatalysts can promote the sluggish oxygen evolution process involving four-electron transfer. Herein, we prepare mesoporous spinel oxide nanosheets and develop an efficient strategy using Fe substitution to enable mesoporous NiCo2O4 nanosheets to generate superior active centers for the OER. Additionally, the iron substitution also promotes the preoxidation of Co/Ni and facilitates the formation of active species. Raman spectroscopy data reveal that the active species of mesoporous NiCo2O4 nanosheets for the OER is NiCo2O4 itself, and the active species of Fe substitution in NiCo2O4 nanosheets are Ni(Co) oxyhydroxides. Therefore, the iron substitution is beneficial to facilitate the transformation of spinel NiCo2O4 into active Ni(Co) oxyhydroxides under OER conditions. Owing to the mesoporous nanosheet structure and the formation of oxyhydroxide active species, the optimized mesoporous Fe0.2Ni0.8Co2O4 nanosheet catalyst exhibits a low overpotential of 270 mV to deliver a current density of 10 mA cm-2 and a small Tafel slope of 39 mV dec-1 for the oxygen evolution reaction in alkaline media.

(Invited) Highly Active OER Electrodes Derived from Fe-Doped Ni Oxyfluoride Formed by Anodizing of NiFe Electrodeposits

Because of the limited availability of fossil fuels and pertinent global environmental issues, hydrogen production via electrochemical water splitting using renewable resources is an important alternative for future energy economies. For efficient alkaline water electrolysis to produce hydrogen, we need to develop highly active and durable electrocatalysts, particularly for oxygen evolution reaction (OER) because of high overpotential. Anodizing of metals and alloys is a promising means of directly fabricating an OER electrocatalyst on a metallic current collector. Binder-free electrocatalysts are readily formed by anodizing. Since Fe-doped Ni oxyhydroxides and hydroxides are recently reported as highly active OER electrocatalysts in alkaline media. Here, we report anodizing of NiFe electrodeposits in fluoride-containing ethylene glycol electrolyte and the conversion of resultant nanoporous Fe-doped Ni oxyfluoride to highly OER active hydroxide during OER (1).NiFe alloy films containing 7.2 – 21.1 at% Fe were obtained by electrodeposition on Ni substrate. Then, the alloys were anodized at 10 V in ethylene glycol electrolyte containing ammonium fluoride and water. The anodizing developed a porous layer consisting of crystalline NiF2 phase. XPS analysis revealed the presence of Fe and O as well as Ni and Fe. Thus, porous Fe-doped Ni oxyfluoride was developed by anodizing. The as-anodized NiFe alloys were initially less active for OER in 1.0 mol dm-3 KOH, but during potential cycling to OER potential, the OER activity was gradually enhanced. The enhancement was dependent upon Fe content, and the highest activity was obtained for the Ni-11.8 at% Fe. After activation, the porous layer was converted to amorphous hydroxide, and the fluoride content was highly reduced. Thus, anodically formed Fe-doped oxyfluoride on the NiFe electrodeposits is a suitable precursor of highly active OER electrocatalyst. The galvanostatic durability test exhibited the stable overpotential, disclosing the high durability of this electrocatalyst.Reference N. Yamada, S. Kitano, Y. Yato, D. Kowalski, Y. Aoki and H. Habazaki, ACS Applied Energy Materials, in press, doi.org/10.1021/acsaem.0c02362.

Vertical Alignment of Fe-Doped <i>β</i>‑Ni Oxyhydroxides for Highly Active and Stable Oxygen Evolution Reaction

The layered transition metal oxyhydroxides have received increasing interest owing to the efficient energy conversion performance and material stability during oxygen evolution reaction (OER). In particular, Fe-doped Ni oxyhydroxides (NiOOH) have shown the record-high OER performance in alkaline media among various catalysts. Theoretically, under-coordinated facets including Ni4+, exposed at the edges of NiOOH, were predicted to perform highly active OER. Therefore, here we suggest a rational catalyst design that exposes NiOOH edges with Fe-doping, which could improve dramatically the OER performance. This unique structure was successfully prepared by electro-anodization process of Fe‑doped Ni octahedral nanocrystals. After anodization, metallic surface of the nanocrystal was transformed to vertically aligned β‑Fe/NiOOH layers with exposed Ni4+ edge sites. Electrochemical OER and anion exchange membrane based single-cell tests recorded the overpotential of 210 mV at a current density of 10 mA cm−2GEO and stable operation for 5 days, respectively. In-situ/operando studies revealed that the cycle of Ni oxidation state between +2 and +4 assisted by Fe dopant is the key engine that greatly accelerates OER kinetics, and that the aligned β‑Fe/NiOOH layers on Ni octahedra are stable under harsh OER conditions.

Surface reconstruction of Ni doped Co–Fe Prussian blue analogues for enhanced oxygen evolution

The in situ generated Ni(Co) oxyhydroxides sites transform the RDS for OER, thus achieving significantly accelerated catalysis kinetics.

Ni(II)/Ni(III) redox couple endows Ni foam-supported Ni2P with excellent capability for direct ammonia oxidation

Converting ammonia in wastewater into harmless nitrogen is a green strategy and electrochemical advanced oxidation processes (EAOP) based on electron transfer are the important means to realize this strategy. As a typical EAOP, ammonia oxidation catalyzed by high-valence transition metal anodes is one of the most effective and greenest conversion measures. Hence, in this study we constructed an electrocatalytic ammonia oxidation system using a nickel phosphide anode (Ni2P/NF). When the initial concentration of ammonia was 1000 mg l−1, and the current was 10 mA, the Faraday efficiency of Ni2P/NF in ammonia oxidation catalysis reached 52.8%. In addition, the Ni2P/NF anode could stabilize the electrolysis of ammonia for up to 24 h. When the voltage was higher than 1.44 V vs. RHE, two peaks appeared at 479 cm−1 and 558 cm−1 in the in situ Raman spectrum and the corresponding current on the CV curve increased rapidly, which revealed that Ni oxyhydroxides formed on the reconstructed surface of Ni2P/NF were the real active sites for catalyzing the ammonia decomposition. The generated intermediates nitrate and nitrite were detected based on the in situ FTIR and spectrophotometric analysis. According to the experimental findings, we proposed a possible pathway for ammonia removal based on the participation of the Ni(II)/Ni(III) redox couple. This study enriched the in-depth understanding of ammonia oxidation and provided a very promising way to treat ammonia containing wastewater.

Temperature-regulated reversible transformation of spinel-to-oxyhydroxide active species for electrocatalytic water oxidation

The active species of NiCo2O4for OER is found to be NiCo2O4at room temperature, and Ni(Co) oxyhydroxides at 45 °C. The alternate change of the reaction temperature induce reversible transformation between NiCo2O4and Ni(Co) oxyhydroxides.

Formation of unexpectedly active Ni-Fe oxygen evolution electrocatalysts by physically mixing Ni and Fe oxyhydroxides.

We present an unusual, yet facile, strategy towards formation of physically mixed Ni-Fe(OxHy) oxygen evolution electrocatalysts. We use in situ X-ray absorption and UV-vis spectroscopy, and high-resolution imaging to demonstrate that physical contact between two inferior Ni(OH)2 and Fe(OOH) catalysts self-assemble into atomically intermixed Ni-Fe catalysts with unexpectedly high activity.

Understanding and Tailoring the Performance of Transition Metal Oxides for the Oxygen Evolution Reaction

The oxygen evolution reaction (OER) is the bottleneck in direct solar and electrocatalytic water splitting cells, and rechargeable aqueous metal-air batteries. Improving the cost-efficiency of these devices requires development of efficient and cheap oxygen evolving catalysts. A good catalyst material should fulfil several important criteria: the composition and structure should be stable at conditions of interest, it should be able to conduct electrons from the active site, and it should be sufficiently active to catalyze water oxidation to oxygen. We explore three different oxide classes comprising 1st row transition metals 1) pristine and doped Co and Ni oxyhydroxides (ox-hy), 2) pristine and doped perovskite oxides ABO3 (A is the earth-alkali or lanthanide metal and B the 1st row transition metal) and 3) pristine and doped αMnO2 as catalysts for the oxygen evolution reaction in neutral to alkaline pH. The emphasis in the analyses is placed on the three most important performance parameters: structural stability, catalytic activity and electronic conductivity. For the ox-hy class we systematically investigate the influence of the nano-scale structure going from 3D catalysts to 2D nanosheets; we examine different edge and terrace terminations, as well as the effect of all stable metal dopants on the performance at pertinent potentials. We identify Fe doped Co, and V, Fe, Ru, Ir and Rh doped Ni ox-hys, as the best catalyst materials, out of which Rh doped Ni ox-hys exhibits the highest activity. Furthermore, we find that the electronic conductivity changes with the nature and valence of the dopant atom, which in turn depends on potential. For the perovskite oxides, we identify Fe4+, Co3+(IS), Ni3+ and Mn3+/Mn4+ pairs as electronically conductive species and distinguish among three different conduction types: intrinsic conductance (Fe4+, Co3+(IS) and Ni3+), electron polaron hoping in Mn compounds with mixed valences and conduction via oxygen 2p and metal 3d holes in the valence band. We investigate whether the performance of αMnO2, which according to many studies is the most active MnO2 polymorph, can be further improved by means of doping. Through a systematic approach we identify Pd doped αMnO2 to be a stable and highly active catalyst for the oxygen evolution reaction. This work was supported by the Horizon 2020 framework, grant number 646186.

In Situ Activating Ubiquitous Rust towards Low‐Cost, Efficient, Free‐Standing, and Recoverable Oxygen Evolution Electrodes

AbstractDeveloping effective ways to recycle rusted stainless steel and to promote the sluggish oxygen evolution reaction (OER), associated with water splitting and metal–air batteries, is important for a resource‐sustainable and environment‐friendly society. Herein, we propose a strategy to enable rusted stainless steel plate to be used as an abundant and low‐cost OER catalyst, wherein a hydrothermal combined in situ electrochemical oxidation–reduction cycle (EORC) method is developed to mimic and expedite the corrosion process, and thus activate stainless steel into free‐standing OER electrodes. Benefiting from the plentiful electrolyte‐accessible Fe/(Ni) oxyhydroxides, high conductivity and mechanical stability, this electrode exhibits remarkable OER performances including low overpotential, fast kinetics, and long‐term durability. The slight degradation in current after long‐term use can be repaired immediately in situ by an EORC.