Cobalt Carbonate Hydroxide Research Articles

Cobalt hydroxide–cobalt carbonate competitive growth on carbonate surfaces

The presence of mineral surfaces can affect the outcome of geochemical reactions by providing alternative nucleation pathways, but not in ways that can yet be reliably quantified. In this work, the reaction of Co(II) with calcite (CaCO3) and magnesite (MgCO3) powders at room temperature was used to quantify the effects of the nature of the mineral substrate and of solution chemistry on the competitive heterogeneous growth between cobalt carbonate (CoCO3) and cobalt hydroxide (Co(OH)2). Experiments were first performed to determine the appropriate solubility product constants of CoCO3 and Co(OH)2, for which several values have been reported in the literature. X-ray photoelectron spectroscopy measurements were then performed to quantify the relative proportion of each phase in surface precipitates as a function of the nature of the substrate, initial saturation level, and pH. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were also used to characterize the morphology and composition of surface precipitates. On calcite powders, Co(OH)2 formed predominantly despite the initial solutions being more supersaturated with respect to CoCO3 than to Co(OH)2, indicating that the kinetics of heterogenous growth were faster for Co(OH)2 than for CoCO3. In contrast, magnesite powders were much more favorable to the growth of CoCO3 because of the low lattice mismatch between the two phases, which allowed for heteroepitaxial growth. However, the proportion of CoCO3 in surface precipitates decreased with increasing initial supersaturation, likely due to the resulting decrease of the free energy barrier for Co(OH)2 nucleation and the rapid kinetics of Co(OH)2 growth. Lowering pH increased the proportion of CoCO3 on both substrates. These findings highlight how the interplay between lattice mismatch, heterogeneous nucleation barriers, and rates of heterogenous growth can influence competitive heterogeneous growth and dramatically affect the outcome of geochemical reactions.

Cobalt carbonate hydroxide hydrate nanowire array modified by sulfur doping for aqueous asymmetric supercapacitors

Cobalt carbonate hydroxide hydrate (CCHH) is usually used as precursor for cobalt oxides yet its intrinsic potential for supercapacitors is usually ignored owing to its poor conductivity and low practical capacitance. In this work, low-content sulfur doping in CCHH hierarchical nanowire array grown on nickel foam (CCHH/NF) greatly improves its conductivity while preserving its unique micromorphology. Accordingly, the obtained Co3S4-CCHH/NF electrode delivers a high specific capacitance of 2.10 F cm−2 at 12.5 mA cm−2 (∼6 times the CCHH/NF). Furthermore, due to the synergistic effect of the CCHH and S elements, a unique micromorphology reconstruction transforms the nanowire array to a porous nanosheet net structure. The newly formed structure provides more electroactive sites, thus further increasing the specific capacitance from 2.10 to 3.95 F cm−2 at 12.5 mA cm−2. Although the huge volume expansion accompanied with the micromorphology reconstruction also weakens the contact between the active material and NF which results in capacitance decay, the preponderance of the enhanced electroactive sites gives rise to an excellent cycling stability of the Co3S4-CCHH/NF by maintaining 165.9% of the initial capacitance after 11,000 cycles. When coupled with a conductive carbon cloth (CC) anode, the Co3S4-CCHH/NF//CC aqueous asymmetric supercapacitor also holds outstanding cycling performance (142.6% of the initial capacitance after 20,000 cycles). This work provides a facile and promising method to obtain high-performance Co-based electrodes for aqueous supercapacitors.

Triphasic Metal Oxide Photocatalyst for Reaction Site‐Specific Production of Hydrogen Peroxide from Oxygen Reduction and Water Oxidation

AbstractThe search for photocatalysts allowing the highly active, selective, and stable conversion of molecular oxygen into hydrogen peroxide is of worldwide interest. Here, the authors report the efficient conversion of O2 into H2O2 with ≈100% selectivity and stable cycle stability by a triphasic metal oxide photocatalyst with a cobalt hydroxide carbonate nanosheet phase for water oxidation as well as iron oxide and titanium oxide phases of a core‐shell morphology for charge transfer and oxygen reduction, denoted as CFT. The different surface energies of 0.78 (anatase) and 0.93 J m‐2 (rutile) for titanium oxide and 1.39 J m‐2 for iron oxide result in a core‐shell morphology. The band gaps for iron oxide (2.02 eV), titanium oxide (≈3 eV), and cobalt hydroxide carbonate (3.80 eV) sites reveal that the CFT photocatalyst allows visible‐to‐UV light absorption. The 18O2 isotope‐labeling experiments prove that the core‐shell structure promotes hole transfer toward the water oxidation site. Additionally, the hole‐induced H2O2 decomposition at the oxygen reduction site is efficiently hindered. Moreover, the photogenerated electrons transfer toward the oxygen reduction site to produce H2O2 from O2 with ≈10‐fold higher activity than those by conventional single‐ or dual‐phase photocatalysts, while giving robust cycle stability.

Electron modulation of cobalt carbonate hydroxide by Mo doping for urea-assisted hydrogen production

Combining urea oxidation reaction (UOR) with hydrogen evolution reaction (HER) is an effective method for energy saving and highly efficient electrocatalytic hydrogen production. Herein, molybdenum-incorporated cobalt carbonate hydroxide nanoarrays (CoxMoyCH) are designed and synthesized as a bifunctional catalyst towards UOR and HER. Benefiting from the Mo doping, the dispersed nanoarray structure and redistributed electron density, the CoxMoyCH catalyst display outstanding catalytic performance and durability for both HER and UOR, affording the overpotential of 82 mV for HER and delivering a low potential of the 1.33 V for UOR (vs. reversible hydrogen electrode, RHE) to attain a current density of 10 mA cm−2, respectively. Remarkably, when CoxMoyCH was applied as bifunctional catalyst in a two-electrode electrolyzer, a working voltage of 1.40 V is needed in urea-assisted water electrolysis at 10 mA cm−2 and without apparent decline for 40 h, outperforming the working voltage of 1.51 V in conventional water electrolysis.

Electronic Structure Modulation and Phase Transformation of Nickel–Cobalt Carbonate Hydroxide Caused by Halogen Doping and Its Effect on Supercapacitor Performance

Nickel–cobalt layered double hydroxides (NiCo-LDHs) have been widely used as supercapacitor materials, and their performance can also be improved by doping engineering. However, the systematic study of halogen anion (X–)-modified NiCo-LDH has rarely been reported. In this study, X– were used to modify nickel–cobalt carbonate hydroxides (NiCo-CHs) via hydrothermal preparation. The halogen doping resulted in changes to the morphology of NiCo-CH. In particular, the electronegativity and electron-withdrawing ability of the halogen were found to be the key to the changes in the metal valence in the NiCo-CHs. Due to the high electronegativity of F, after 12 h of hydrothermal treatment, F-doped NiCo-CH (named F-NCCH12) caused the formation of high-valent M3+ sites, resulting in the production of a NiCo-LDH phase different from other halogen dopings. By varying the hydrothermal reaction time, we identified the mechanism of the structural and phase transition. In addition, by testing the electrochemical properties of NiCo-CHs for their applications as supercapacitors, we found a strong correlation with the doped halogen. Specifically, the supercapacitor performance improved with an increase in the electronegativity of the halogen. Furthermore, density functional theory calculations showed that F doping accelerates the reaction kinetics and improves the conductivity. Finally, we assembled NF@F-NCCH12//AC asymmetric devices, which exhibited an energy density of 35.3 W h kg–1 at a power density of 375 W kg–1. Crucially, the stable phase structure resulted in improved cycle performance of the F-NCCH12 electrode material, which showed an initial specific capacitance retention of 91.6% after 10,000 cycles.

Enhanced electrocatalytic activity of FeNi alloy quantum dot-decorated cobalt carbonate hydroxide nanosword arrays for effective overall water splitting.

The development of earth-abundant catalysts toward high-efficiency overall water splitting is of critical importance for electrochemical hydrogen production. Here, novel FeNi alloy quantum dot (QD)-decorated cobalt carbonate hydroxide (CoCH) nanosword arrays were successfully constructed on Ni foam (FeNi/CoCH/Ni foam) and used as an efficient bifunctional electrocatalyst for overall water splitting in alkaline media. Benefiting from the synergistic effect between the FeNi alloy QDs and CoCH, the FeNi/CoCH/Ni foam electrode delivers a current density of 20 mA cm-2 at an overpotential of 240 mV and a small Tafel slope of 44.8 mV dec-1 for the oxygen evolution reaction (OER). Further, it displays excellent performance for overall water splitting with a voltage of 1.49 V at 10 mA cm-2 and maintains its activity for at least 23 h. In particular, it only needs low cell voltages of 1.54 and 1.6 V to drive high current densities of 100 and 400 mA cm-2, respectively, which is much better than commercial Pt/C/Ni foam‖RuO2/Ni foam, providing great potential for large-scale application.

High-pressure vapor-solid transformation of 2D template to derive 2D Co–N–C electrocatalysts for oxygen reduction reaction

Two-dimensional (2D) cobalt zeolitic imidazolate frameworks (ZIF-67) have attracted significant research interests to synthesize cobalt and nitrogen co-doped carbon-based (Co–N–C) catalyst for oxygen reduction reaction (ORR). However, most of the current synthetic approaches of 2D ZIF-67 are energy-intensive, environmentally hazardous and low-yield. Herein, a feasible and efficient ‘morphology-retaining method via a high-pressure vapor-solid reaction’ are reported to synthesize 2D ZIF-67 nanosheets by using 2D cobalt carbonate hydroxide template. In the strategy, the high-pressure vapor caused by sublimation of 2-Melm and the pores formed from effusion of CO2 during transformation ensure the complete transformation from 2D template to 2D ZIF-67. The corresponding 2D Co–N–C catalyst exhibits comparable ORR electrocatalytic activity and better stability than Pt/C in alkaline media. The present method is expected to offer a feasible and universal way to efficiently synthesize 2D M–N–C catalysts.

Chromium doping: A new approach to regulate electronic structure of cobalt carbonate hydroxide for oxygen evolution improvement

Highly efficient catalysts are required to solve the intrinsically sluggish kinetics of oxygen evolution reaction (OER). Herein, chromium doped cobalt carbonate hydroxide nanowire array on Ni foam (Cr-CoCH/NF) has been synthesized for the enhancement of OER activity and stability. Compared with pure CoCH/NF, Cr0.2-CoCH/NF, the optimal doping of Cr, shows a low overpotential of 203 mV at the current density of 10 mA cm−2 and a small Tafel slope of 84 mV dec−1 in 1.0 M NaOH. In addition, there is little deterioration in electrocatalytic performance after 1000-cycle cyclic voltammetry and the high activity can be maintained over 25 h. Density functional theory calculations reveal the Cr doping can regulate the electronic structure of nearby Co active center to achieve great enhancement of OER activity.

Effects of ammonium chloride on structural stability of cobalt carbonate hydroxide and their improved electrochemical performance for supercapacitor

Transition metal salts are potential materials for energy storage and conversion. However, their application is limited by poor morphology retention and performance stability during charge/discharge processes. Herein, the interlaced rod-like Co(CO3)0.5(OH)·0·11H2O (CCO) are prepared on nickel foam (NF) by hydrothermal method. During the experiment, the reaction solution is changed from weak basic to weak acidity with the increase of NH4Cl, and it has obvious influence on the growth and electrochemical performance of the as-prepared CCO. When the molar ratio of CO(NH2)2/NH4Cl in solution is 1:2.8 (the pH value of solution is 5.42), the microstructure of CCO nanorods (NRs) are obviously different from that obtained by other molar ratios, and many nanofloccules surrounded on their surface. Moreover, they show improved electrochemical performance, and the specific capacities are 2115.1 and 1400 C/g at 1 and 20 A/g, respectively. Especially, the structure of CCO NRs is remained after 3000 electrochemical cycles, and the specific capacity only lost 3% of the initial value, showing their good cycle stability. In addition, an assembled hybrid CCO NRs/NF//AC device can output a specific energy of 41.8 Wh/kg at 850.7 W/kg. These results can fully prove that the as-prepared CCO NRs is a good candidate for high-performance electrode material.

ZIF-67 grown on a fibrous substrate via a sacrificial template method for efficient PM2.5 capture and enhanced antibacterial performance

In the design air filtration materials, surface modification and porosity control are appealing strategies to achieve a higher quality factor. In this study, a sacrificial template method was introduced to obtain hierarchically metal–organic framework (MOF)-loaded micro/nano-backbone fibrous filters. Cobalt carbonate hydroxide hydrate nanoneedle arrays were first grown on polyester fabric as a sacrificial template that provide Co2+ source for constructing a ZIF-67 on micro/nano fibrous backbone substrate, which resulted in a combination of enokitake-like and bead-on-string-like structure simultaneously. This unique structure effectively reduced the pore size of the fabric and provided a modified surface with a maximum exposure of MOFs. As a consequence, the composite fabric filter exhibited excellent PM2.5 removal efficiency of 97.5 ± 1.2%, while with only a small increase in pressure drop (∼14 Pa). Particularly, the PM2.5 filtration quality factor was up to 0.051, which is 200% higher than that of pristine PET. Furthermore, the composite fabric filter showed excellent antibacterial activity against both S. aureus and E. coli. This study facilitated the design of hierarchically MOF-loaded fibrous filter materials with excellent comprehensive filtration performance.

Controllable Morphology of Sea-Urchin-like Nickel-Cobalt Carbonate Hydroxide as a Supercapacitor Electrode with Battery-like Behavior.

Nickel–cobalt carbonate hydroxide with a three-dimensional (3D) sea-urchin-like structure was successfully developed by the hydrothermal process. The obtained structure enables the enhancement of charge/ion diffusion for the high-performance supercapacitor electrodes. The mole ratio of nickel to cobalt plays a vital role in the densely packed sea-urchin-like structure formation and electrochemical properties. At optimized nickel/cobalt mole ratio (1:2), the highest specific capacitance of 950.2 F g–1 at 1 A g–1 and the excellent cycling stability of 178.3% after 3000 charging/discharging cycles at 40 mV s–1 are achieved. This nickel–cobalt carbonate hydroxide electrode yields an energy density in the range of 42.9–15.8 Wh kg–1, with power density in the range of 285.0–2849.9 W kg–1. The charge/discharge mechanism at the atomic level as monitored by time-resolved X-ray absorption spectroscopy (TR-XAS) indicates that the high capacitance behavior in a nickel–cobalt carbonate hydroxide is mainly dominated by cobalt carbonate hydroxide.

Structure-dependent electrochemical properties of cobalt (II) carbonate hydroxide nanocrystals in supercapacitors

In this work, we report the structure-dependent electrochemical performance of cobalt carbonate hydroxide (Co2(OH)2CO3) nanocrystals by experimental investigation and theoretical simulation. Different Co2(OH)2CO3 nanostructures including two-dimensional (2D) nanosheets (NSs) and one-dimensional (1D) nanowires (NWs), were synthesized on self-supported carbon cloth substrates by a facile hydrothermal method. Compared to 1D NWs, 2D Co2(OH)2CO3 NSs provided a short ion transfer path, and low electron transfer resistance during the electrochemical reaction. At the current density of 2 mA cm−2, 2D Co2(OH)2CO3 NSs exhibited a higher area capacitance of 2.15F cm−2 and better cycling performance (96.2% retention after 10,000 cycles) than that of 1D NWs (1.15F cm−2 and 90.1% retention). First-principles density functional theory (DFT) calculations revealed that the band gap of the (120) facet in 2D NSs was 0.2 eV, far less than of the (200) facet in 1D NWs (1.04 eV). Electrochemical impedance spectroscopy (EIS) measurements further indicated that the electron transfer and reaction kinetics were more efficient in 2D NSs. This work can provide an important insight in understanding the mechanism of electrochemical energy storage.

Facile synthesis of P-doped NiCo2S4 nanoneedles supported on Ni foam as highly efficient electrocatalysts for alkaline oxygen evolution reaction

In this work, one-step phosphosulfurization is demonstrated to prepare P-doped nickel cobalt sulfide nanoneedles vertically decorated on nickel foam (P-NiCo2S4/NF) as an extremely efficient electrocatalyst toward the oxygen evolution reaction (OER). The phosphosulfurization is conducted on nickel cobalt carbonate hydroxide in the presence of P2S5. The P-NiCo2S4 nanoneedles on the nickel foam generate a synergistic effect that provides effective mass and electron transfer pathways, endows the electrocatalyst with a moderate electronic structure, and facilitates gas diffusion to enhance the electrocatalytic performance. The catalysts yield a small overpotential of 300 mV to reach a current density of 50 mA cm−2, Tafel slope as low as 70 mV dec−1, and long-term stability over 100 h. These findings highlight the practical feasibility of P-doped NiCo2S4 on NF for water splitting and offer a new approach for efficiently preparing advanced electrocatalysts in the future.

Facile Synthesis of Carbon Cloth Supported Cobalt Carbonate Hydroxide Hydrate Nanoarrays for Highly Efficient Oxygen Evolution Reaction.

Developing efficient and low-cost replacements for noble metals as electrocatalysts for the oxygen evolution reaction (OER) remain a great challenge. Herein, we report a needle-like cobalt carbonate hydroxide hydrate (Co(CO3)0.5OH·0.11H2O) nanoarrays, which in situ grown on the surface of carbon cloth through a facile one-step hydrothermal method. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations demonstrate that the Co(CO3)0.5OH nanoarrays with high porosity is composed of numerous one-dimensional (1D) nanoneedles. Owing to unique needle-like array structure and abundant exposed active sites, the Co(CO3)0.5OH@CC only requires 317 mV of overpotential to reach a current density of 10 mA cm−2, which is much lower than those of Co(OH)2@CC (378 mV), CoCO3@CC (465 mV) and RuO2@CC (380 mV). For the stability, there is no significant attenuation of current density after continuous operation 27 h. This work paves a facile way to the design and construction of electrocatalysts for the OER.

NiCoSx@Cobalt Carbonate Hydroxide Obtained by Surface Sulfurization for Efficient and Stable Hydrogen Evolution at Large Current Densities.

Developing earth-abundant, active, and stable electrocatalysts for hydrogen evolution reactions (HERs) at large current densities has remained challenging. Herein, heterostructured nickel foam-supported cobalt carbonate hydroxide nanoarrays embellished with NiCoSx nanoflakes (NiCoSx@CoCH NAs/NF) are designed via room-temperature sulfurization, which can drive 10 and 1000 mA cm-2 at low overpotentials of 55 and 438 mV for HER and exhibit impressive long-term stability at the industrial-level current density. Surprisingly, NiCoSx@CoCH NAs/NF after a 500 h stability test at 500 mA cm-2 exhibit better catalytic performance than the initial one at high current densities. Simulations showed that NiCoSx@CoCH NAs have an optimized hydrogen adsorption free energy (ΔGH*) of 0.02 eV, owing to the synergistic effect of CoCH (ΔGH* = 1.36 eV) and NiCoSx (ΔGH* = 0.03 eV). The electric field at the heterostructure interface leads to electron transport from CoCH to NiCoSx, which enhances HER dynamics. The hierarchical nanostructure has a large specific area and a superaerophobic surface, which are beneficial to hydrogen generation/release for efficient and stable HER.

Polypyrrole decorated cobalt carbonate hydroxide on carbon cloth for high performance flexible supercapacitor electrodes

Polypyrrole decorated cobalt carbonate hydroxide on carbon cloth (PPy@CoCH/CC) has been synthesized by a simple and cost-effective hydrothermal method. The prepared PPy@CoCH/CC exhibits unique 3D hierarchical nanostructure, showing uniform decoration of PPy nanoparticles on CoCH nanosheets. The PPy@CoCH/CC composites exhibit enhanced electrochemical performances due to the enhanced electrical conductivity, pseudocapcitive behavior, and efficient ion transport of PPy. Specifically, The PPy@CoCH/CC composites show high specific capacitance of 1217 F·g−1 at a current density of 1 A·g−1 and a good cycling performance of 89% capacity retention after 8000 cycles. In addition, a symmetric supercapacitor is fabricated using the PPy@CoCH/CC composites as both positive and negative electrode. The prepared symmetric supercapacitors deliver a high energy density of 47.36 Wh·kg−1 at a power density of 1600 W·kg−1.

Rich Se nanoparticles modified cobalt carbonate hydroxide as an efficient electrocatalyst for boosted hydrogen evolution in alkaline conditions

Nonprecious metal hydroxides are promising electrocatalyst candidates for oxygen evolution reaction. However, their hydrogen evolution reaction (HER) performance is not satisfactory, which limits their application for water splitting. Herein, a facile electrodeposition reduction strategy was applied to fabricate rich Se nanoparticles modified cobalt carbonate hydroxide nanoarrays on carbon cloth (Se NPs/CoCH NAs/CC) with η10 of 84.3 mV for HER, which is much smaller than that of original CoCH NAs/CC (η10 = 347.7 mV). The superior performance of Se NPs/CoCH NAs/CC was due to its large active surface area, rich active sites, and synergistic effect between Co-Se. DFT simulations also revealed that free energy for atomic hydrogen adsorption is much lower on Se NPs/CoCH (0.75 eV) than on CoCH (1.36 eV). Moreover, this work offered a simple and efficient strategy for developing hierarchical selenium/hydroxides with outstanding HER performance, which contributed to the cost and energy savings for mass hydrogen production.

Supercapattery electrode materials by Design: Plasma-induced defect engineering of bimetallic oxyphosphides for energy storage

Although transition metal hydroxides are promising candidates as advanced supercapattery materials, they suffer from poor electrical conductivity. In this regard, previous studies have typically analyzed separately the impacts of defect engineering at the atomic level and the conversion of hydroxides to phosphides on conductivity and the overall electrochemical performance. Meanwhile, this paper uniquely studies the aforementioned methodologies simultaneously inside an all-in-one simple plasma treatment for nickel cobalt carbonate hydroxide, examines the effect of altering the nickel-to-cobalt ratio in the binder-free defect-engineered bimetallic Ni-Co system, and estimates the respective quantum capacitance. Results show that the concurrent defect-engineering and phosphidation of nickel cobalt carbonate hydroxide boost the amount of effective redox and adsorption sites and increase the conductivity and the operating potential window. The electrodes exhibit ultra-high-capacity of 1462 C g−1, which is among the highest reported for a nickel–cobalt phosphide/phosphate system. Besides, a hybrid supercapacitor device was fabricated that can deliver an energy density of 48 Wh kg−1 at a power density of 800 W kg−1, along with an outstanding cycling performance, using the best performing electrode as the positive electrode and graphene hydrogel as the negative electrode. These results outperform most Ni-Co-based materials, demonstrating that plasma-assisted defect-engineered Ni-Co-P/POx is a promising material for use to assemble efficient energy storage devices.

Engineering superhydrophilic/superaerophobic hierarchical structures of Co-CH@NiFe-LDH/NF to boost the oxygen evolution reaction

3D superhydrophilic/superaerophobic hierarchical “rod-sheet” structure of NiFe-based layered double hydroxides coupled with cobalt carbonate hydroxide (Co-CH@NiFe-LDH/NF) has been synthesized on Ni foam by a Fe3+ ion hydrolysis-induced etching-growth approach under hydrothermal conditions. The Co-CH@NiFe-LDH/NF electrode demonstrates excellent oxygen evolution reaction (OER) performances, which mainly result from the synergic effect between Co-CH and NiFe-LDH. The unique stepped hierarchical “rod-sheet” structure of Co-CH@NiFe-LDH/NF not only benefits the inherent catalytic activity, but also enhances the electron transfer and increases the exposed active sites. Moreover, the superhydrophilic/superaerophobic joint properties of Co-CH@NiFe-LDH/NF promote the diffusion of aqueous electrolyte and ensure the rapid release of bubbles. Furthermore, a water-splitting device has been assembled with commercial Pt/C/NF and Co-CH@NiFe-LDH/NF as cathode and anode, respectively, which can work stably for 200 h without obvious degradation. Hence, the strategy of engineering stepped hierarchical structures with synergistic effect may offer a new pathway to synthesizing highly efficient OER electrocatalysts.

N and Mn dual-doped cactus-like cobalt oxide nanoarchitecture derived from cobalt carbonate hydroxide as efficient electrocatalysts for oxygen evolution reactions

Collaborative design in both nanoarchitecture and electronic structure is of great significance for cost-effective electrocatalysts towards oxygen evolution reaction (OER). Herein, cactus-like porous cobalt oxide (Co3O4) nanoarchitecture doped with manganese cation and nitrogen anion (N-Mn-Co3O4) was fabricated on the nickel foam by hydrothermal and subsequent N2 plasma treatment. Unique hierarchical structure and surface atomic engineering endow the N-Mn-Co3O4 with rich active sites, abundant oxygen vacancies, enhanced electrical conductivity and rapid ion diffusion. Hence, as electrocatalysts for OER, the N-Mn-Co3O4 exhibits low overpotentials of 302 and 320 mV to drive the current density of 50 and 100 mA cm−2, respectively, and superior stability over 40 h under alkaline environments. More strikingly, when assembling the N-Mn-Co3O4 with Pt/C anode into an alkaline electrolyzer, the system delivers a small voltage of 1.55 V at the current density of 10 mA cm−2 with excellent durability. This work may shed light on design and fabrication of efficient OER electrocatalysts by synergistically tailoring electronic and geometric structures.