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A hierarchical Cu2+1O nanowire covered ultrathin Sn/Cu6Sn5 alloy composite on copper foam is produced in 90 minutes by a fully electrochemical wet process for use as a stable Li metal anode to prevent the formation of Li dendrite.

The electrolysis of water using renewable energy inputs is a promising sustainable approach to produce clean hydrogen fuel. The conventional water electrolysis, where the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are tightly coupled to satisfy the thermodynamic potential of at least 1.23 V, occasionally encounters gas crossover through the membrane, resulting in the formation of explosive gas mixtures and reactive oxygen species. In this study, an asymmetric cell design of 3 M H2SO4|V(II)/V(III)|1 M KOH equipped with nickel foam electrodes is used for achieving decoupled HER and OER under kinetically favorable conditions by dividing the process into two steps using vanadium ions as redox mediators. The actual overall water splitting at an average cell voltage of 1.3 V and a current density of 10 mA cm−2 is accomplished even in the presence of membranes with outstanding cycling stability. The well-designed system for decoupled water electrolysis can allow the production of clean energy fuel using a low-power input in renewables–to–hydrogen conversion.

Herein, incremental capacity-differential voltage (IC-DV) at a high C-rate (HC) is used as a non-invasive diagnostic tool in lithium-ion batteries, which inevitably exhibit capacity fading caused by multiple mechanisms during charge/discharge cycling. Because battery degradation modes are complex, the simple output of capacity fading does not yield any useful data in that respect. Although IC and DV curves obtained under restricted conditions (

As the oxygen evolution reaction (OER) imposes a high energy barrier during electrochemical water splitting, designing highly efficient, stable, and cost-effective electrocatalysts for OERs is an ongoing challenge. In this study, we present a facile approach to prepare villi-shaped Ni-Fe hydroxides incorporated with oxalate derived from Ni-Fe oxalate through the in situ precipitation growth and subsequent immersion in an alkaline solution. The electrode with an optimized Ni-Fe ratio improves the OER kinetics, on which the electronic structure of the active site is adjusted based on a mutual effect between the adjacent nickel and iron atoms. The OER performance was significantly better than that of monometallic Ni(OH)2 and pristine Ni foam, with a low overpotential of 277 mV at 100 mA cm-2 and excellent stability. The enhanced OER performance is ascribed to the advanced intrinsic electrocatalytic activity of the electrode as a result of the synergetic effect of optimized Ni-Fe ratio mixing at the atomic level which leads to an increased surface area, a high number of active sites, and a reduced charge transfer resistivity.

Silicon monoxide (SiO) is regarded as a strong candidate for next-generation lithium ion battery anode materials because of its high energy density, low cost, and relatively low volume expansion compared to silicon (Si). However, the intrinsic low electrical conductivity and non-negligible volume expansion limit the practical application of SiO. Herein, dual-carbon-confined hydrangea-like SiO clusters are developed via chemical vapor deposition (CVD) growth, followed by a spray drying approach as a novel anode material for high-performance and stable lithium ion batteries. The evolution of the buffer layer along with sufficient void spaces to alleviate the volume expansion, besides the increased electrical conductivity, contributes to the improved discharge capacity of 1071 mAh g−1 after 200 cycles at a high current density of 0.75 A g−1 with a low expansion ratio of 9%. The distinct dual-carbon-confined hydrangea-like structure leads to synergistic improvements in battery performance, which will pave the way for promoting the commercial application of silicon-based anode materials.

Lithium-ion batteries (LIBs) with high energy density and safety under fast-charging conditions are highly desirable for electric vehicles. However, owing to the growth of Li dendrites, increased temperature at high charging rates, and low specific capacity in commercially available anodes, they cannot meet the market demand. In this study, a facile one-pot electrochemical self-assembly approach has been developed for constructing hybrid electrodes composed of ultrafine Fe

In this study, 10 μm-thick TiO2 nanotube arrays (TNAs) coated with a MoO3 layer were prepared by electrochemical oxidation on titanium foil followed by successive cyclic voltammetric deposition, aiming at the fabrication of a thick binder-free anode with high capacity and good cycling stability for lithium ion batteries (LIBs). Through the evaluation of the electrochemical performance of electrodes prepared under various conditions, the electrode obtained at a precursor concentration of 5 mM showed the best electrochemical performance, exhibiting high reversible capacity and enhanced cycling stability. With the structural advantage and intrinsic characteristics of TNAs, the large volume expansion of MoO3 is successfully accommodated, resulting in 97% retention at a rate of 5 C over 500 cycles and 91% retention even at a high rate of 25 C.

In this study, vertically aligned p–n junction TiO2 nanotubes can be formed by anodization of the Ti substrate following the addition of a high electric field in a Pd precursor-containing electrolyte. The bottom region of the TiO2 nanotubes with a high concentration of Pd because of the high electric field which was induced to be p-type. In contrast, the region with a low Pd concentration (top of the TiO2 nanotubes) was determined to be n-type, similar to the pristine TiO2. The concentration profile of the dopant in TiO2 nanotubes was investigated via TOF-SIMS and XPS. Defect formation energies in TiO2 nanotubes were estimated using density-functional theory calculation to understand the p–n junction formation. The p–n junction TiO2 nanotubes showed a high photocatalytic hydrogen production rate of 25.2 μL cm−2 h−1 under solar light irradiation as a result of the enhancement of visible light photoactivity.

Herein, we present a simple and innovative method for preparing Ni–Fe oxide doped with trace amounts of Ru on a stainless steel 304 substrate by single-step anodization. The procedure yields a highly efficient, durable, and flexible bifunctional catalyst for water splitting. The material exhibits outstanding electrocatalytic performance with high stability in both the hydrogen and oxygen evolution reactions, owing to the enhanced activity resulting from the incorporation of a small amount of Ru into anodic Ni–Fe oxide and a change in morphology that facilitates mass transfer. A stable cell voltage of 1.83 V is achieved at a current density of 100 mA cm−2 in a symmetric electrolyzer composed of flexible Ru-doped Ni–Fe oxide electrodes that can be formed into various shapes. The applicability of bifunctional electrodes of various shapes is demonstrated by their excellent stability for 100 h.

International audience; Herein we report a wet-chemical process to obtain binder-free anodes for lithium-ion batteries (LIBs) using a straightforward and easily scalable approach. Electrochemical deposition, anodization, and electropolymerization are used to firmly attach a nanoporous and flexible SnO2 film, uniformly coated with polyaniline (PANI), onto a Cu substrate. The three-dimensional, flexible, and nanoporous SnO2@PANI electrodes exhibit good specific capacity, capacity retention, and charge transfer resistance. Its favorable electrochemical properties are attributed to the large surface area, high electrical conductivity, and effective reduction of volume expansion. These results demonstrate that the proposed approach to forming SnO2@PANI electrodes is a promising strategy for constructing high-performance binder-free anodes for emerging flexible LIBs.

Co@Co3O4 nanoparticles highly dispersed on N-doped porous carbon (Co,N–C/TOCNF) were prepared by pyrolysis of the Zn/Co bimetallic ZIF-8/67 in situ grown on the carboxylated cellulose nanofibers (TOCNF) at 900 °C. The physicochemical properties of the material were examined using various instruments, and it was applied as an electrocatalyst for oxygen reduction reaction. The interconnected three-dimensional network in TOCNF prevented aggregation of the catalytically active Co nanoparticles and enhanced electron transfer and mass diffusion, and Co,N–C/TOCNF showed excellent catalytic performance in alkaline medium with improved stability compared to the one by the commercial Pt/C catalyst.

As the oxygen evolution reaction (OER) imposes a high energy barrier during electrochemical water splitting, designing highly efficient, stable, and cost-effective electrocatalysts for OERs is an ongoing challenge. In this study, we present a facile approach to prepare villi-shaped Ni-Fe hydroxides incorporated with oxalate derived from Ni-Fe oxalate through the

International audience; Stainless steel, a cost-effective material comprising Fe, Ni, and Cr with other impurities, is considered a promising electrode for green electrochemical energy storage and conversion systems. However, the Cr in stainless steel and its passivating property in electrochemical systems hinder the commercial use of stainless steel in the energy conversion and storage industry. Therefore, many studies have revealed the usability of stainless steel by developing various surface treatment techniques to modify the electrode surface to take advantage of the intrinsically active elements in stainless steel. In this review, we present the recent advances and breakthroughs in surface treatment approaches to adjust surface composites and the electrochemical performance and rational design of electrodes in green energy storage and conversion systems, including (photo)electrochemical water splitting, Li-ion batteries, and supercapacitors. © 2022 Elsevier B.V.

Anodic TiO2 nanotubes were simultaneously grown and doped with RuO2 by single-step anodization in a negatively-charged RuO4− precursor. Subsequently, a high positive voltage was imposed on the nanotubes in an F−-based electrolyte (a process referred to as potential shock), which led to the formation of a through-hole RuO2-doped TiO2 nanotube membrane without significant loss of the RuO2 catalyst. XPS results confirmed that the doped Ru metal was converted into RuO2 as the potential shock voltage increased. Further increases in the potential shock voltage led to the formation of RuOx/Ru in the TiO2 nanotubes. All of our results clearly showed that a through-hole catalyst-doped TiO2 nanotube membrane can be produced by a sequence consisting of single-step anodization and the potential shock process.

Ant-nest nanostructured α-Fe2O3 films with a thickness of 10 μm are anodically grown on stainless steel without any binder, and the resulting material functioned as a current collector in the negative electrode of Li-ion batteries. Phase of Fe2O3 in the structure is the key factor determining the battery performance for a high capacity and cyclability. For example, single anodization allows Fe to be dissolved faster than other components such as Cr, resulting in a high Cr ratio in the stainless steel, which deteriorates the retention of the battery capacity during cycling. On the other hand, the Fe–Cr–Ni ratio is not significantly changed if a proper pretreatment for activation, which is able to dissolve all components with a similar dissolution rate in the subsequent anodization step, is performed. The anodic ant-nest nanostructures play a vital role in not only the pathway of Li ions but also releasing the stress of volume expansion during Li insertion/extraction. The optimized electrode delivers a high reversible capacity of 737 μAh cm−2 (737 mAh cm−3 or 1157 mAh g−1) at a current density of 650 μA cm−2 (1 C-rate) and sustains up to 500 cycles with only 0.13% capacity fading per cycle.

A high-purity copper foil was passivated in aqueous solution of 1.0 M NaOH at −200 mV at room temperature. Top-view micrographs were taken after 30, 90, 150 and 600 s of passivation. Nanowires with a diameter of up to 56 nm, consisting of Cu2O and CuO were obtained. The mechanism of the nanowires growth was investigated based on the current density–time curves, relevant micrographs and morphology analyses. It was found that the nuclei is formed at electrolyte-electrode interface, leading to the formation of the first bunches of nanowires. Then, nanowires grow by the expansion and decomposition of the formed oxide bunches in the electrolyte, which can be understood through the current density – time curves.

Electropolished copper foil was passivated in aqueous solution of 1.0 M NaOH at negative potential range vs. silver chloride electrode at room temperature. The passivations were performed at −50, −100, −150, and −200 mV for 1, 5 or 15 h. The resulting nano-needle layers were characterized by X-ray photoelectron spectroscopy and band gaps derived from UV–Vis spectroscopy evidencing coincidence of Cu(OH)2, CuO and Cu2O phases. Scanning Electron Microscopy revealed that the diameter of nanoneedles was not influenced by the passivation potential, however, the nanoneedles diameter was decreasing with extension of the passivation time (the smallest diameter obtained was 60 ± 17 nm). Additionally, the as-prepared oxide nano-needles were found to be polycrystalline, without any post treatments. All together, chemical compositionand physical properties (band gap) show that the inner part of the grown nano-needles is rather made of Cu2O, while outer part, there where the passivation reaction takes place, is made of CuO and Cu(OH)2.

A SnO2–TiO2 electrode was prepared via anodization and subsequent anodic potential shock for a binder-free anode for lithium-ion battery applications. Perpendicularly oriented TiO2 microcones are formed by anodization; SnO2, originating in a Na2SnO3 precursor, is then deposited in the valleys between the microcones and in their hollow cores by anodic potential shock. This sequence is confirmed by SEM and TEM analyses and EDS element mapping. The SnO2–TiO2 binder-free anode is evaluated for its C-rate performance and long-term cyclability in a half-cell measurement apparatus. The SnO2–TiO2 anode exhibits a higher specific capacity than the one with pristine TiO2 microcones and shows excellent capacity recovery during the rate capability test. The SnO2–TiO2 microcone structure shows no deterioration caused by the breakdown of electrode materials over 300 cycles. The charge/discharge capacity is at least double that of the TiO2 microcone material in a long-term cycling evaluation.

This paper presents an investigation of anodic TiO2 nanotube arrays (TNAs), with a Co3 O4 /CuO coating, for lithium-ion batteries (LIBs). The coated TNAs are investigated using various analytical techniques, with the results clearly suggesting that the molar ratio of Co3 O4 /CuO in the TiO2 nanotubes substantially influences its battery performance. In particular, a cobalt/copper molar ratio of 2:1 on the TNAs (Co2 Cu1 @TNAs) features the best LIBs anode performance, exhibiting high reversible capacity and enhanced cycling stability. Noticeably, Co2 Cu1 @TNAs achieve excellent rate capability even after quite a high current density of 20.0 A g-1 (≈25 C, where C corresponds to complete discharge in 1 h) and superior volumetric reversible capacity of ≈3330 mA h-1 cm-3 . This value is approximately seven times higher than those of a graphite-based anode. This outstanding performance is attributed to the synergistic effects of Co2 Cu1 @TNAs: 1) the structural advantage of TNAs, with their large amount of free space to accommodate the large volume expansion during Li+ insertion/extraction and 2) the optimized ratio of Co3 O4 and CuO in the composite for improved capacity. In addition, no binder or conductive agent is used, which is partly responsible for the overall improved volumetric capacity and electrochemical performance.

In this paper, I investigate what effect school capital investments have on housing values and household location choice in the context of the Tiebout model. This research identifies an exogenous v...

Submerged arc plasma technology was assessed for the removal of phenols from wastewater. The OH radicals generated from the boundary between the plasma and waste solution were considered as a significant factor on the degradation reaction. In this study, the effects of highly energetic electrons released from the submerged arc plasma were mainly studied. The highly energetic electrons directly broke the strong chemical bond and locally increased the reaction temperatures in solution. The effects of the submerged-arc plasma on the decomposition of phenol are discussed in terms of the input energy and initial concentration. The single use of submerged arc plasma easily decomposed the phenol but did not increase the mineralization efficiency. Therefore, the submerged arc plasma, coupled with the ozone injection, was investigated. The submerged arc plasma combined with ozone injection had a synergic effect, which led to significant improvements in mineralization with only a small increase in input energy. The decomposition mechanism of phenol by the submerged arc plasma with the ozone was analyzed.

We investigated the effects of applied potential and anodizing time on the morphological and structural changes of TiO2 microcones for different electrolytes. We found that the mean diameter of the TiO2 microcones produced in (COOH)2 linearly increased with the applied voltage, whereas in other electrolytes, the mean diameters converged to a constant value. Regardless of the type of electrolyte used, the percentage of area occupied by the TiO2 microcones is estimated at 20% of the entire surface when the microcones are fully-grown and well-dispersed. All the TiO2 microcones are composed of the anatase phase, the intensity of which increases in the XRD spectra as the voltage or anodizing time increases. We identified the formation mechanism of the TiO2 microcones using early stage current density-time transient graphs and SEM images.

Deep eutectic solvents (DESs) are a common successor to ionic liquids (ILs) with similar physicochemical properties. DESs have attracted considerable interest in related chemical research based on the superiority of DESs over ILs and in the preparation of porous materials. In addition, DESs-based materials have been applied widely in chemical research. This review highlights the preparation and properties of DESs. The application of DES in the preparation of silica and polymers is also discussed. The available data and references in this field are reviewed to summarize the applications and developments of DESs. Based on the development of DESs, the exploitation of new DES-based materials is expected to diversify into chemical research.

Zinc ricinoleate (Zn(Ri)2) exhibits excellent selectivity and the capability to remove odor-active compounds, such as nitrous compounds (NH3 and organic nitrogen) and sulfurous compounds (H2S, organic sulfides, and mercaptans). In contrast with the conventional catalyst-(or enzyme)-aided process, in this study, Zn(Ri)2 was prepared on zinc foil by a facile electrochemical approach. The electrochemically synthesized Zn(Ri)2 was characterized and compared to commercially available Zn(Ri)2, which clearly indicated that the average size and the production yield are strongly dependent on the external bias and anodization time: an increase in the diameter from 9.3 µm at 30 V to 15.2 µm at 80 V. In particular, an external bias of 80 V afforded the most stable particle structure and highest production yield. During anodization, the particles agglomerate and grow to form larger particles. With a distinct spherical morphology, the increased surface area contributes to the enhanced odor-removing capacity of 88% in 30 min, which is 2.3 times stronger than that of the commercial product.

In this study, we investigated the addition of a tungsten catalyst into the electrolyte of a vanadium redox flow battery (VRBs) and measured the cell performance with respect to the concentration of the W 6+ precursor. The VRBs showed a clear improvement in electrochemical performance because of the deposition of tungsten on the electrode. The presence of tungsten allowed the ionization of tungsten in the electrolyte during battery cycling. The optimized concentration of the tungsten additive was examined using electrochemical methods, which showed that the efficiency of the VRBs improved by 2–3% after the addition of 3 mM tungsten to the electrolyte. In particular, the performance of VRB cells in an anolyte containing a W 6+ catalyst was significantly enhanced at high current rates.

This study aims to investigate the electrochemical co-deposition of a Cu-Sn alloy to substitute for the Ni undercoating layer between the outmost coating layer and substrate. The electrodeposition was performed in a sulfuric acid bath containing a mixture of additives such as complex agent (EDTP), auxiliary complex agent (TEA), chelating agent, and pit prevent agent. The effect of each additive on co-deposition was studied by cyclic voltammetry using a rotating disk electrode, which showed that each additive helps to shift the reduction onset potential of Cu closer to that of Sn, thus resulting in uniform Cu-Sn coating. Electroplating of the Sn-rich Cu-Sn alloy was performed for various current densities and plating times, and the results showed that a bright-white-colored, thick, uniform, and compact layer of the above alloy can be deposited under optimized conditions (1 A dm −2 and 30 min). Based on the results of SEM, EDS mapping, XPS, and XRD, we found that Cu and Sn were uniformly distributed throughout the deposited layer with almost equal contents when a relatively low current density (less than 3 A dm −2 ) was employed.

A uniformly colored TiO 2 , on which the surface is functionalized with nanotubes to control wettability, was prepared by a two-step anodization; the first anodization was carried out to prepare nanotubes for a super-hydrophilic or -hydrophobic surface and the second anodization was performed to fabricate a thin film barrier oxide to ensure uniform coloring. The effect of the nanotubes on barrier oxide coloring was examined by spectrophotometry and UV-vis-IR spectroscopy. We found four different regimes governing the color changes in terms of anodization voltage, indicating that the color of the duplex TiO 2 was primarily determined by the thickness of the barrier oxide layer formed during the second anodization step. The surface wettability, as confirmed by the water contact angle, revealed that the single barrier TiO 2 yielded 74.6° ± 2.1, whereas the nanotubes on the barrier oxide imparted super-hydrophilic properties as a result of increasing surface roughness as well as imparting a higher hydrophobicity after organic acid treatment.

We formed various TiO2 nanotube layers by anodizing Ti metal under various conditions of anodization temperature and time. By controlling these conditions, we could adjust the morphology of the TiO2 nanotubes in terms of length and wall thickness. Subsequent annealing converted the TiO2 nanotubes into crystallized nanostructures. TiO2 nanotubes of different crystalline phases had different mechanical properties. To evaluate the mechanical properties of the TiO2 nanotubes in detail, they were subjected to Vickers hardness testing. The TiO2 nanotube layers showed wide variations in hardness depending upon the anodization and annealing temperatures.

Die cast, high-Si content ADC12 Al alloy samples were successfully anodized without surface cracks. This was accomplished with a 0.3 M sulfuric acid electrolyte with a high concentration of sodium aluminate. During anodization, the AlO2- anions were attracted to the positively-charged Al substrate and deposited in the cracks formed by un-oxidized Si islands within the ADC12. Anodic films prepared in electrolytes with a high concentration of AlO2- drastically enhanced surface morphology, thickness uniformity, Vickers hardness, and corrosion behavior in comparison with anodic film prepared without AlO2- concentration. The simultaneous sealing mechanism by AlO2- anions during anodization is reported in detail.

The simultaneous doping of RuO 2 and IrO 2 catalysts into anodic TiO 2 nanotubes (NTs) was successfully achieved by single-step anodization. KRuO 4 was used as the precursor for the RuO 2 dopant. However, for IrO 2 doping, IrO x nanoparticles (NPs) were synthesized from IrCl 3 as an intermediate species to avoid damage to the NTs by chloride ions during doping. IrO 4 − generated from the IrO x NPs through selective dissolution in the electrolyte was simultaneously doped into the positively biased TiO 2 NTs along with RuO 2 . The structural features, NT length, and amount of catalyst doping were controlled by the concentration of HF in the electrolyte and the anodizing time. The binary-catalyst-doped TiO 2 NTs exhibited an outstanding onset potential of 0.84 V for the oxygen evolution reaction (OER). In addition, the amount of O 2 gas evolved during the OER at 2.0 V was measured to be 230 μmol cm −2 min −1 by gas chromatography, which corresponds to a faradaic efficiency of 99%. The major oxidation states of the metals in the catalysts were found to be Ru 4+ and Ir 4+ by X-ray photoelectron spectroscopy and transmission electron microscopy selected area electron diffraction analysis, indicating the presence of RuO 2 and IrO 2 in the TiO 2 NTs.

In this study, the key anodization parameters of titanium for the formation of microcones were studied in detail. As the voltage increases, titanium oxides tend to transform from amorphous nanotubes to anatase microcones under certain electrolyte conditions. We found that a very small amount of H2SO4 is essential for the formation of microcones. In addition, if the concentration of HF is too small, a barrier-type oxide is formed. In contrast, the surfaces of the formed nanotubes are quickly dissolved at high concentrations of HF. The formed microcones have an average diameter of 2.58 μm and a height of 3.88 μm. The formation mechanism of the TiO2 microcones is related to the changes in the molar volumes of titanium metal and its oxide. From the current-time transients, the current density is considerably higher during the formation of TiO2 microcones compared to the formation of other structures, indicating that a high current leads to extremely high local heating, resulting in the amorphous-to-anatase phase transformation.

A fast and non-toxic sealing method based on the use of NaAlO 2 solution is investigated in detail. AlO 2 sealing is carried out using NaAlO 2 as the sealant, which is neutralized with H 2 SO 4 and optimized to pH 7. Temperature, sealing time, pH is optimized in terms of chemical/mechanical properties, measured by Vickers hardness test, Tafel analysis, and sealing quality test based on ASTM-B680. The Vickers hardness, corrosion resistance, and sealing properties of the samples obtained by the proposed sealing method are found to be superior compared to those of the samples prepared by the conventional sealing methods. XPS data show a high intensity of boehmite (AlOOH) peaks in the sample obtained by the NaAlO 2 -based sealing, similar to the case of the sample obtained by hydrothermal sealing. During the NaAlO 2 sealing process, a hard and dense layer of boehmite, which is formed from the dissipated AlO 2 − present in the sealant solution and the dissolved anodic oxide, is deposited within the pores of the anodic alumina in a short time; this leads to enhanced chemical/mechanical properties of the anodic porous alumina sample sealed using NaAlO 2 .

CuC2 O4 ⋅x H2 O was facilely prepared on a Cu-Ni alloy substrate by in situ precipitation-induced growth by using a mixture of sodium persulfate, hydrogen peroxide, and oxalic acid. Thermal annealing allowed the conversion of CuC2 O4 ⋅x H2 O to leaf-like CuO nanostructures with a thickness of a few tens of micrometers of sub-sized nanoparticles, which were applied for fabricating binder-free anodes for lithium-ion batteries. Ni was a nucleation site for CuC2 O4 ⋅x H2 O, which was uniformly formed on the entire substrate. The concentration of each component in the mixture solution caused significant morphological changes because of the different elution of copper ions. CuO nanostructures annealed at 550 °C showed large areal and gravimetric capacity with excellent capacity retention of 95.5 % after 200 cycles at a high current density because of their appropriate structural morphology, which not only allowed the formation of a stable solid electrolyte interphase layer but also enabled a reversible reaction during the charge/discharge process.

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Stainless steel-based electrocatalysts have attracted tremendous attention as alternatives to precious noble metal-based catalysts for renewable energy research, as they are readily available and inexpensive. Herein, self-activated anodic nanoporous stainless steel is demonstrated as a highly efficient and durable electrode with improved catalytic performance for the hydrogen evolution reaction. Etched and anodized stainless steel (EASS) is prepared by anodization using etched stainless steel 304 foil with a rough surface, followed by thermal annealing. Due to its extremely high surface area, evolved oxygen vacancies, and excellent durability for 100 h at 100 mA cm−2, EASS that has been annealed in an Ar/H2 atmosphere (EASS-Ar/H2) exhibits an overpotential of 370 mV, lower than that of pristine etched stainless steel electrode (466 mV) in 1 M KOH aqueous solution. In contrast, EASS annealed in air (EASS-air) displays no catalytic activity. Interestingly, the overpotential of EASS-Ar/H2 is further reduced to 244 mV after 10,000 cycles of linear sweep voltammetry by self-activation due to the generation of Ni-rich hydroxide with increasing oxygen vacancies.