Electrochemical Oxygen Evolution Research Articles

FeNi alloys incorporated N-doped carbon nanotubes as efficient bifunctional electrocatalyst with phase-dependent activity for oxygen and hydrogen evolution reactions

Electrochemical oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are two important half-cell reactions for overall water splitting. The rational design and fabrication of efficient electrocatalysts involving nonprecious-metals and carbon matrix is highly attractive. Herein, a series of N-doped carbon nanotubes encapsulated FeNi alloy nanoparticles (FeNi@NCNTs) are synthesized via a simple pyrolysis treatment of Fe-doped Ni(OH)2 precursors under the assistance of dicyandiamine source. The results reveal that the Fe/Ni ratio has an obvious influence on the morphology and phase composition of FeNi@NCNTs series, thus affecting the electrocatalytic performance. The highest electrocatalytic activity is achieved for the Fe1Ni4@NCNTs product with a Fe/Ni molar ratio of 1:4, which delivers low overpotentials of 278 and 279 mV for OER and HER at 10 mA cm−2 in 1.0 mol/L KOH, respectively. The intriguing electrocatalytic performance is mainly ascribed to the advantageous integration of rambutan-like hierarchically porous structure and composition optimization, significantly facilitating the fast mass/charge transfer as well as promoting the adsorption ability for intermediates. The present method may open a facile avenue for developing cost-effective, high-activity, and stable electrocatalysts for the application of overall water splitting.

Oxidized phosphorus linking promotes the activity of a cobalt molecular assembly for electrochemical oxygen evolution

Molecular assemblies represent a classical type of active electrocatalysts for oxygen evolution reaction (OER), while the practical application is limited by the relatively low electrical conductivity. Herein, a cobalt molecular assembly was synthesized and supported by a conductive phosphorus doped graphene. It served as a potential OER electrocatalyst by affording a current density of 10 mA cm−2 at a small overpotential of 390 mV, and the turnover frequency of cobalt sites was increased by 21.5 times comparing to the assembly supported by the pristine graphene. Our observations unveil that the potential linking of oxidized phosphorus atoms in the carbon matrix is mainly responsible for the high activity of cobalt molecular assembly. The overall OER catalytic cycle was analyzed by in situ attenuated total reflectance-surface enhanced infrared absorption spectroscopy, suggesting that the formation of *OOH species on the cobalt sites could be critical for the final evolution of oxygen. These results open a potential avenue into the exploration of highly active OER electrocatalysts toward replacing the noble metals based electrocatalysts.

Construction of iron-modulated VN/V3O4/Co5·47N nanoparticles with rich heterogeneous interfaces for efficient oxygen evolution reaction

With the increasing need of clean energy demand, the development of efficient and green electrocatalysts for water electrolysis plays an irreplaceable role in the realization of large-scale production of hydrogen. Herein, an original iron modulated heterogeneous VN/V3O4/Co5·47N nanoparticles (FVOCN) is successfully synthesized using hydrothermal technique and in situ pyrolysis protocol. Through a series of characterization, it is found that the addition of iron in VN/V3O4/Co5·47N (VOCN) can significantly regulate the electronic structure and make it have better electrochemical oxygen evolution activity in 1 M KOH solution as opposed to the VOCN. The catalyst is obtained at the sintering temperature of 600 °C has the best performance, which only requires a lower overpotential of 270 mV to attain the current density of 10 mA cm−2 and superior to commercial IrO2. The method of introducing iron into vanadium-based, cobalt-based nitrides and vanadium-based oxides can broaden the research content of new electrochemical oxygen evolution reaction (OER) catalysts and provide a reference idea for the development of energy industry.

Binuclear Metal Phthalocyanines with Enhanced Activity in the Oxygen Evolution Reaction: A First-Principles Study.

The rational design of efficient catalysts for the electrochemical oxygen evolution reaction (OER) critically relies on a comprehensive understanding of the reaction mechanisms. Herein, the alkaline OER on planar mononuclear metal phthalocyanines (MPc, where M = Mn, Co, Fe, and Ni) and binuclear metal phthalocyanines (bi-MPc) is studied using density functional theory (DFT) methods. Both FePc and bi-CoPc exhibit enhanced stability and OER activity, with the energy required for the leaching of central metal being as high as 2.28 and 2.45 eV and the overpotentials of the OER being 0.48 and 0.57 V, respectively. Through electronic structure analysis, it is found that, in the OER process of bi-MPc, the large macrocyclic ligand and metal ions not bonding with the intermediate can serve as hole reservoirs. Intermediate species are further stabilized by the dispersal of a positive charge, reducing the free energy. These findings underscore the significance of macrocyclic ligands in the rate-determining step of the OER catalyst.

Tetranuclear CoII4O4 Cubane Complex: Effective Catalyst Toward Electrochemical Water Oxidation.

The reaction of Co(OAc)2·6H2O with 2,2'-[{(1E,1'E)-pyridine-2,6-diyl-bis(methaneylylidene)bis(azaneylylidene)}diphenol](LH2) a multisite coordination ligand and Et3N in a 1:2:3 stoichiometric ratio forms a tetranuclear complex Co4(L)2(μ-η1:η1-OAc)2(η2-OAc)2]· 1.5 CH3OH· 1.5 CHCl3 (1). Based on X-ray diffraction investigations, complex 1 comprises a distorted Co4O4 cubane core consisting of two completely deprotonated ligands [L]2- and four acetate ligands. Two distinct types of CoII centers exist in the complex, where the Co(2) center has a distorted octahedral geometry; alternatively, Co(1) has a distorted pentagonal-bipyramidal geometry. Analysis of magnetic data in 1 shows predominant antiferromagnetic coupling (J = -2.1 cm-1), while the magnetic anisotropy is the easy-plane type (D1 = 8.8, D2 = 0.76 cm-1). Furthermore, complex 1 demonstrates an electrochemical oxygen evolution reaction (OER) with an overpotential of 325 mV and Tafel slope of 85 mV dec-1, required to attain a current density of 10 mA cm-2 and moderate stability under alkaline conditions (pH = 14). Electrochemical impedance spectroscopy studies reveal that compound 1 has a charge transfer resistance (Rct) of 2.927 Ω, which is comparatively lower than standard Co3O4 (5.242 Ω), indicating rapid charge transfer kinetics between electrode and electrolyte solution that enhances higher catalytic activity toward OER kinetics.

Preparation and application research of transition metal phosphides

Due to the serious environmental pollution in the world, the shortcut to harmonious development is to improve traditional disposable energy and identify new energy sources that can be utilized. The current problem that human society must solve is to discover and use efficient and inexhaustible new energy sources, among which electrolytic water technology is an effective way to develop clean energy. In recent years, researchers have focused on producing hydrogen by electrolyzed water, but the intermediate hydrogen evolution reaction and the oxygen evolution reaction are relatively slow kinetic processes, and they cannot give the factory a large range of electrolytic water hydrogen production work and push down the commercialization process, so improving the rate of electrolytic water process must be an efficient catalyst. Transition metal phosphide is one of the non-precious metal catalysts in the electrochemical hydrogen evolution reaction and oxygen evolution reaction. Transition metal phosphide can promote rapid change of chemical reaction rate, and it has the characteristics of being cheap and easy to operate so it has a great prospect in the electrolysis of water. In this experiment, the oxygen evolution performance was optimized based on the crystal surface regulation of cobalt-doped transition metal nickel phosphide. The optimal reduction time and a small overpotential (60 mV) were obtained by using sodium borohydride to reduce the sample.

Enhanced electrochemical oxygen generation from sillenite phase of bismuth iron oxide (Bi24Fe2O39) ultrafine particles stabilised at room temperature

Recently, lot of research is going on in development of clean energy-based technology to address the issue of exponentially increasing energy demands. Electrochemical water splitting is a clean and efficient process for generation of H2 and O2. Water electrolysis produces hydrogen and oxygen on cathode and anode respectively as separate half-cell reactions is one of the most important clean alternative processes. This work reports synthesis of Bi24Fe2O39 ultrafine crystalline nanoparticles via facile room temperature chemical method for the first time. Bi24Fe2O39 shows a spherical morphology with an average size of 8 nm. As obtained Bi24Fe2O39 acts as an electrocatalyst for electrochemical oxygen evolution reaction (OER). Electrochemical oxygen generation studies confirm the overpotential of 420 mV in 1 M KOH solution at a current density of 10 mA/cm2. Tafel slope and EIS studies give further insight of oxygen generation process. The results show that Bi24Fe2O39 exhibits low Tafel slope of 63 mV dec−1 and a very low charge transfer resistance of ∼10 Ω. This study paves a new way for future research into bismuth based sillenite structure for various energy related applications.

Nickel and Commercially Available Nickel‐Containing Alloys as Electrodes for the Electrochemical Oxygen Evolution

AbstractWater electrolysis is a crucial technology for independency on fossil fuels. However, water splitting is limited by the sluggish kinetics of oxygen evolution reaction (OER). While many studies report highly active, non‐precious metal‐based electrocatalysts for alkaline OER, applicability under industrial conditions is often omitted. Such conditions require catalysts being applied on nickel or nickel‐containing alloys in elevated electrolyte concentrations. In contrast to the rather inert substrates often used in scientific studies, such industrially applied substrates exhibit significant OER activity themselves and show dynamic behaviour. Therefore, it is crucial to understand the OER behaviour of such substrates. Here, nickel and seven commercially available nickel‐containing alloys are investigated as anodes in alkaline OER and their elemental compositions correlated to their corresponding activities. Repeated potential cycling across the Ni(II)/Ni(III)‐redox couple is established as activity‐enhancing procedure. Overall, the nickel‐base alloy Hastelloy® X exhibits the highest activity due to its Fe‐, Cr‐, Mo‐ and Co‐content. Though, the activity gain differs significantly for the various materials. Comparing Ni and Hastelloy® X as least and most active materials, the positive impact of activation on both activity and stability becomes evident. While untreated Ni suffers from poor OER stability, the activity‐enhancing procedure also significantly increases electrode stability in 24 h chronopotentiometry.

Tri-metallic fluoride nanoplates immobilized on reduced graphene architectures as efficient oxygen evolution reaction catalyst

Exploring the transition metal fluoride-based catalysts with highly catalytic activity is of great importance to satisfy the electrochemical oxygen evolution reaction (OER). Herein, the tri-metallic (cobalt, iron, and nickel) fluorides immobilizing on reduced graphene oxide architectures (CoFeNiF-rGAs) are constructed by hydrothermal and low-temperature fluoridation. The hierarchical structure assembled by the π-π configuration of graphene can provide abundant channels for fast ion diffusion and guarantee the uniform loading of metal fluorides. Owing to the hierarchical morphology and the formation of metal fluorides/graphene interfaces, CoFeNiF-rGAs can show excellent OER performance. Only 238 mV of overpotential is required to achieve a current density of 10 mA cm−2 in alkaline electrolyte, and the Tafel slope (78.8 mV dec-1) and charge transfer resistance (13.6 Ω) are smaller than the control samples, respectively, implying a fast kinetic behavior during OER. The highly catalytic stability of CoFeNiF-rGAs is confirmed by 1000 cyclic voltammetry and chronoamperometry test for 20 h, and the boosted catalytic mechanism is elucidated by density function theory calculation.

Enhancement of the electrochemical oxygen evolution reaction by light and external magnetic fields, using hybrid electrodes made by Langmuir–Blodgett

The implementation of water electrolysis technology is hampered by the slow kinetics of the oxygen evolution reaction. In an attempt to solve this issue, anodes which are able to respond to external stimuli such as magnetic field and light were successfully prepared by the Langmuir–Blodgett technique, using Fe3O4 magnetic nanoparticles (FTO/Fe3O4) and Fe3O4 nanoparticles together with tetrathiafulvalene as photosensitizer (FTO/Fe3O4/TTF).This technique allowed obtaining highly stable and homogeneous anodes in a simple and reproducible way. The electrodes produced a catalytic effect on the water oxidation reaction, without the use of a noble-metal, and proved to be sensitive to a 365 nm LED light as well as to an external magnetic field. Water oxidation reaction was evaluated by linear sweep voltammetry, by the Tafel slopes and also by electrochemical impedance spectroscopy. This work presents new perspectives for the water oxidation reaction, using electrodes fabricated by the Langmuir–Blodgett technique and catalyzed through the use of external stimuli such as light and magnetic fields.

Fast and In-Depth Reconstruction of Two-Dimension Cobalt-Based Zeolitic Imidazolate Framework in Glucose Oxidation Processes.

Currently, metal-organic frameworks (MOFs) have emerged as viable candidates for enduring electrode materials in nonenzyme glucose sensing. However, given the inherent water susceptibility of MOFs and their complete self-reconstruction during the process of electrochemical oxygen evolution in alkaline conditions, we are motivated to explore the truth of MOFs catalyzing glucose oxidation. In this work, we fabricated a two-dimensional cobalt-based zeolitic imidazolate framework (ZIF-L) as the electrode material for catalyzing glucose oxidation in alkaline conditions. Our explorations revealed that while the initial glucose catalytic response varied among ZIF-L samples with differing thicknesses, the ultimate steady-state catalytic performance remained largely consistent. This phenomenon arose from the transformation of ZIF-L with distinct thicknesses into CoOOH with uniform morphological and structural characteristics during the glucose catalysis process. And in situ Raman spectroscopy elucidated the sustained equilibrium within the glucose catalytic system, wherein the dynamic interconversion between CoOOH and Co(OH)2 governs the overall process. This study contributes to an enhanced understanding of the glucose catalytic mechanism aspects of nonenzymatic glucose sensor electrode materials, offering insights that serve as inspiration for the development of advanced glucose electrode materials.

Steering surface reconstruction of hybrid metal oxides for efficient oxygen evolution reaction in water splitting and zinc-air batteries

Surface reconstruction yields real active species in electrochemical oxygen evolution reaction (OER) conditions; however, rationally regulating reconstruction in a targeted manner for constructing highly active OER electrocatalysts remains a formidable challenge. Here, an electrochemical activation strategy with selective etching was utilized to guide the reconstruction process of a hybrid cobalt-molybdenum oxide (CoMoO4/Co3O4@CC) in a favorable direction to improve the OER performance. Both in-situ Raman and multiple ex-situ characterization tools demonstrate that controlled surface reconstruction can be easily achieved through Mo etching, with the formation of a dynamically stable amorphous-crystalline heterostructure. Theoretical calculations together with experimental results reveal that the synergistic effects between amorphous CoOOH and crystalline Co3O4 are crucial in enhancing the catalytic performance. Consequently, the reconstructed CoMoO4/Co3O4@CC exhibits a low overpotential of 250 mV to achieve a current density of 10 mA cm−2 in 1 M KOH, and more importantly it can be practiced in electrolytic water splitting and rechargeable zinc-air batteries devices, achieving ultra-long stability for over 500 and 1200 h, respectively. This work provides a promising route for the construction of high-performance electrocatalysts.

Composition‐Dependent NiS‐Enriched FeNi2S4/ZnCr2O4 Catalyst for Electrochemical Oxygen Evolution Reaction

AbstractTransition metal sulfide and oxide nanomaterials are gaining popularity as catalysts for electrochemical water splitting because of their cost effectiveness, durability, and stability without using noble metals. Our study focuses on a hybrid electrocatalyst, NiS‐enriched FeNi2S4/ZnCr2O4, which is synthesized in two steps by sol‐gel followed through thermal decomposition in an aqueous solution by a hydrothermal process. We investigated its potential application in the electrochemical oxygen evolution reaction (OER). Powder X‐ray diffraction and X‐ray photoelectron spectroscopy analyses were used to determine the chemical composition and structure. The results showed that the FeNi2S4 structure has an enriched NiS phase. Additionally, the morphology of the synthesized FeNi2S4/ZnCr2O4 was revealed by field emission scanning electron microscopy (FE‐SEM). Under alkaline (1 M KOH) conditions, the FeNi2S4/ZnCr2O4 hybrid nanostructure showed a low overpotential value of 295 mV (Tafel slope, 59 mV dec−1) for OER activities due to the synergistic effects of FeNi2S4 and ZnCr2O4. Furthermore, the hybrid nanostructure demonstrated its long‐term stability and efficiency as an electrocatalyst for OER activities, surpassing previously reported superior electrocatalysts and state‐of‐the‐art materials.

Magnetic field enhanced surface reconstruction of Fe2P and the promotional effect in electrochemical oxygen evolution

In recent years, the utilization of magnetic fields to enhance the oxygen evolution reaction (OER) performance of catalysts has emerged as an effective approach. However, current research primarily focusing on the impact on magnetic transition metal oxides, and the relevant mechanisms are still worth further exploration. Here, the OER performance of Fe2P loaded on carbon paper (Fe2P/CP) and nickel foam (Fe2P/NF) substrates under in situ magnetic field was investigated. It is revealed that magnetic fields can substantially enhance the OER performance of Fe2P/CP and Fe2P/NF. With a magnetic field of 1.0 T, the current density of 75-Fe2P/CP increases by 28 times (1.8 V vs. RHE), leading to a maximum magnetic current density percentage of 2770%. According to our results, the magnetic enhancement effect is highly correlated with the surface reconstruction of Fe2P to α-FeOOH with lower OER energy barriers. Additionally, the spin pinning effect is observed on the α-FeOOH/Fe2P interfaces, which leads to the rapid alignment of spin electrons on the surface of catalysts under magnetic field, lowering the OO coupling energy barrier, and therefore improve OER kinetics. These discoveries have the potential to contribute to a fundamental and comprehensive understanding of electrochemical reactions involving magnetic fields.

Atomistic Modeling of Spinel Oxide Particle Shapes and Reshaping under OER Conditions

The surface configurations of the low-index facets of a set of spinel oxides are investigated using DFT+U calculations to derive surface energies and predict equilibrium nanoparticle shapes via the Wulff construction. Two very different conditions are investigated, corresponding to application either in heterogeneous catalysis or in electrocatalysis. First, the bare stoichiometric surfaces of NiFe2O4, CoFe2O4, NiCo2O4, and ZnCo2O4 spinels are studied to model their use as high-temperature oxidation catalysts. Second, focusing attention on the electrochemical oxygen evolution reaction (OER) and on the CoFe2O4 inverse spinel as the most promising OER catalyst, we generate surface configurations by adsorbing OER intermediates and, in an innovative study, we recalculate surface energies taking into account adsorption and environmental conditions, i.e., applied electrode potential and O2 pressure. We predict that under OER operating conditions, (111) facets are dominant in CoFe2O4 nanoparticle shapes, in fair agreement with microscopy measurements. Importantly, in the OER case, we predict a strong dependence of nanoparticle shape upon O2 pressure. Increasing O2 pressure increases the size of the higher-index (111) and (110) facets at the expense of the (001) more catalytically active facet, whereas the opposite occurs at low O2 pressure. These predictions should be experimentally verifiable and help define the optimal OER operative conditions.

Conductive nitrogen-doped carbon armored MOF-derived Fe doped nickel sulfide for efficient oxygen evolution reaction

Developing clean energy sources is vital amid the global energy crisis. Hydrogen, emerging as a sustainable energy vector via water electrolysis, mandates adept catalysts owing to the sluggish electrochemical oxygen evolution reaction (OER) kinetics. This work provides a three-step synthesis of Fe-doped NiS2 catalyst from metal-organic frameworks (MOFs). By encapsulating with nitrogen-doped carbon (NC) armor derived from polypyrrole (PPy) through thermal annealing, a novel Fe–NiS2@NC catalyst is achieved for improving the OER performance. The Fe–NiS2@NC demonstrates outstanding prowess, achieves a current density of 10 mA cm−2 with an overpotential as modest as 255 mV, accompanied with a Tafel slope of only 77 mV dec−1. Furthermore, it maintains operational stability for over 40 h under demanding conditions of 50 mA cm−2, displaying an impressive durability compared to the pure NiS2 catalyst. This work combines Fe-doping in NiS2 and PPy-derived NC encapsulation, achieving a dual enhancement of activity and stability of the catalyst. And this strategy also offers a feasible pathway to simultaneously boost the activity and stability in OER electrocatalysts, significantly contributing to clean energy solutions and providing ideas for future research.

Coordinately unsaturated single Fe-atoms with N vacancies and enhanced sp3 carbon defects in Fe-N(sp2)-C structural units for suppression of cancer cell metabolism and electrochemical oxygen evolution.

Installing coordinately unsaturated Fe-N-C structural units on polymer-composite-derived N-doped carbon offers highly active Fe-Nx sites for the electrochemical oxygen evolution reaction (OER) and reactive oxygen species (ROS) generation in tumor cells. An NH4Cl-driven high-temperature etching method was employed for the formation of FeSA950NC with coordinately unsaturated single Fe-atoms in an Fe-N(sp2)-C structural unit together with N vacancies (VN) and sp3 defects. The carbonization of Fe-phen@ZIF-8 at 800 °C for 30 min under argon, followed by grinding Fe-ZIF-8@RF-urea with NH4Cl at 950 °C for 2 hours, resulted in sp3 carbon defects and VN sites with coordination unsaturation in Fe-Nx due to NH4Cl decomposition to NH3 and HCl, which produced substantial internal stress for etching the carbon matrix. FeSA950NC was used to treat both A549 lung cancer cells and NIH3T3 mouse fibroblast cells to determine its potential as an efficient tumor therapeutic strategy using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and ROS assays. Additionally, FeSA950NC provided high stability and excellent OER activity through the Fe-N(sp2)-C structural unit on pyridinic nitrogen by delivering at a minimum overpotential of 300 mV, which is much lower than that of structurally similar Fe-atom sites. The significantly stronger ROS and OER activities of FeSA950NC suggested the role of VN and sp3-carbon defects with coordinately unsaturated Fe-N2 sites in improving its catalytic performance.

Elucidating the performance of hexamethylene tetra-amine interlinked bimetallic NiCo-MOF for efficient electrochemical hydrogen and oxygen evolution.

Bimetallic metal-organic frameworks (MOFs) play a significant role in the electrocatalysis of water due to their large surface area and availability of increased numbers of pores. For the inaugural time, we examine the effectiveness of a hexamethylene tetra-amine (HMT)-induced 3D NiCo-MOF-based nanostructure as a potent bifunctional electrocatalyst with superior performance for overall water splitting in alkaline environments. The structural, morphological, and electrochemical properties of the as-synthesized bifunctional catalyst were examined thoroughly before analyzing its behavior towards electrochemical water splitting. The HMT-based NiCo-MOF demonstrated small overpotential values of 274 mV and 330 mV in reaching a maximum current density of 30 mA cm-2 for hydrogen and oxygen evolution mechanisms, respectively. The Tafel parameter also showed favorable HER/OER reaction kinetics, with slopes of 78 mV dec-1 and 86 mV dec-1 determined during the electrochemical evaluation. Remarkably, the NiCo-HMT electrode exhibited a double-layer capacitance of 4 mF cm-2 for hydrogen evolution and 23 mF cm-2 for oxygen evolution, while maintaining remarkable stability even after continuous operation for 20 hours. This research offers a valuable blueprint for implementing a cost-effective and durable MOF-based bifunctional catalytic system that has proven to be effective for complete water splitting. Decomposition of water under higher current densities is crucial for effective long-term generation and commercial consumption of hydrogen.

Fe doping and interface engineering-induced dual electronic regulation of CoSe2/Co9S8 nanorod arrays for enhanced electrochemical oxygen evolution

Double electronic modification by Fe doping and interface engineering boosts the OER performance of Fe-doped CoSe2/Co9S8 nanorod arrays.

Evolution of Mn-Bi2O3 from the Mn-doped Bi3O4Br electro(pre)catalyst during the oxygen evolution reaction.

Mn-doped Bi3O4Br has been synthesized using a solvothermal route. The undoped Bi3O4Br and Mn-Bi3O4Br materials possess orthorhombic unit cells with two distinct Bi sites forming a layered atomic arrangement. The shift in the (020) plane in the powder X-ray diffraction (PXRD) pattern confirms Mn-doping in the Bi3O4Br lattice. Elemental mapping indicated 7% Mn doping in the Bi3O4Br lattice structure. A core-level X-ray photoelectron study (XPS) indicates the presence of BiIII and MnII valence-states in Mn-Bi3O4Br. Doping with a cation (MnII) containing a different charge and ionic radius resulted in vacancy/defects in Mn-Bi3O4Br which further altered its electronic structure by reducing the indirect band gap, beneficial for electron conduction and electrocatalysis. The irreversible MnII to MnIII transformation at a potential of 1.48 V (vs. RHE) precedes the electrochemical oxygen evolution reaction (OER). The Mn-doped electrocatalyst achieved 10 mA cm-2 current density at 337 mV overpotential, while the pristine Bi3O4Br required 385 mV overpotential to reach the same activity. The pronounced OER activity of the Mn-Bi3O4Br sample over the pristine Bi3O4Br highlights the necessity of MnII doping. The superior activity of the Mn-Bi3O4Br catalyst over that of Bi3O4Br is due to a low Tafel slope, better double-layer capacitance (Cdl), and small charge-transfer resistance (Rct). The chronoamperometry (CA) study depicts long-term stability for 12 h at 20 mA cm-2. An electrolyzer fabricated as Pt(-)/(+)Mn-Bi3O4Br can deliver 10 mA cm-2 at a cell potential of 2.05 V. The post-CA-OER analyses of the anode confirmed the leaching of [Br-] followed by in situ formation of Mn-doped Bi2O3 as the electrocatalytically active species. Herein, an ultra-low Mn-doping into Bi3O4Br leads to an improvement in the electrocatalytic performance of the inactive Bi3O4Br material.