Efficient Oxygen Evolution Electrocatalysts Research Articles

Orange peel derived activated carbon supported Ni–Co3O4 as an efficient electrocatalyst for oxygen evolution and reduction reaction in alkaline media

This study focuses on the development of a cost-effective electrocatalyst with excellent activity and stability for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR), which is crucial for water electrolysis and fuel cell technologies. Waste orange peel is utilized as a carbon precursor to synthesize biomass-derived activated carbon (OPAC) with a unique three-dimensional sheet-like microstructure. Subsequently, a simple hydrothermal method is employed to modify the OPAC by introducing Ni-doped Co3O4, leading to the formation of a Ni–Co3O4/OPAC hybrid. We propose the Ni–Co3O4/OPAC hybrid as a highly efficient bifunctional electrocatalyst for both OER and ORR. Co3O4/OPAC and Co3O4 catalysts are also prepared for comparison. Remarkably, the Ni–Co3O4/OPAC hybrid exhibits significantly enhanced OER activity compared to Co3O4/OPAC and Co3O4 catalysts. It demonstrates a lower overpotential of 360 mV and a lower Tafel slope of 55.47 mV/dec, indicative of more efficient electrochemical performance. Moreover, in the ORR analysis, the Ni–Co3O4/OPAC hybrid displays a two-step pathway and achieves a higher ORR limiting current density compared to the Co3O4/OPAC and Co3O4 catalysts. These results highlight the synergistic effects of Ni and Co species, along with the unique properties of the OPAC support, which contribute to the enhanced activity, stability, and electron transfer characteristics of the Ni–Co3O4/OPAC hybrid. Furthermore, the improved electrical conductivity of the Ni–Co3O4/OPAC hybrid makes it a promising candidate for applications in metal-air batteries and other energy conversion devices. The utilization of waste orange peel as a carbon precursor and the facile synthesis method demonstrate the potential for cost-effective and sustainable electrocatalyst production. Overall, the Ni–Co3O4/OPAC hybrid represents a significant advancement in electrocatalyst design and holds promise for advancing the field of energy conversion and storage.

Constructing Dual-Phase Co9S8-CoMo2S4 Heterostructure as an Efficient Trifunctional Electrocatalyst for Oxygen Reduction, Oxygen Evolution and Hydrogen Evolution Reactions.

Designing robust, efficient and inexpensive trifunctional electrocatalysts for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is significant for rechargeable zinc-air batteries and water-splitting devices. To this end, constructing heterogenous structures based on transition metals stands out as an effective strategy. Herein, a dual-phase Co9S8-CoMo2S4 heterostructure grown on porous N, S-codoped carbon substrate (Co9S8-CoMo2S4/NSC) via a one-pot synthesis is investigated as the trifunctional ORR/OER/HER electrocatalyst. The optimized Co9S8-CoMo2S4/NSC2 exhibits that ORR has a half-wave potential of 0.86 V (vs. RHE) and the overpotentials at 10 mA cm-2 for OER and HER are 280 and 89 mV, respectively, superior to most transition-metal based trifunctional electrocatalysts reported to date. The Co9S8-CoMo2S4/NSC2-based zinc-air battery (ZAB) has a high open-circuit voltage (1.41 V), large capacity (804 mAh g-1) and highly stable cyclability (97 h at 10 mA cm-2). In addition, the prepared Co9S8-CoMo2S4/NSC2-based ZAB in series can self-drive the corresponding water-splitting device. The dual-phase Co9S8-CoMo2S4 heterostructure provides not only multi-type active sites to drive the ORR, OER and HER, but also high-speed charge transfer channels between two phases to improve the synergistic effect and reaction kinetics.

NiO/ATO as an efficient bifunctional electrocatalysts for oxygen evolution and urea oxidation reactions

In this study, Ni-MOF-derived NiO was mixed with various weights of commercial antimony-doped tin oxide (ATO) using a simple and efficient hydrothermal method to synthesize composites denoted as AN-1, AN-2, and AN-3, which were subsequently characterized using a variety of physicochemical methods. The as-prepared materials were used as bifunctional electrocatalysts for oxygen evolution reaction (OER) and urea oxidation reaction (UOR). In the UOR, the AN-1 electrocatalyst exhibited excellent performance compared to the other electrocatalysts. In a 1.0 M KOH aqueous electrolyte, the OER onset potential was approximately 1.64 V, whereas, in the UOR, the overpotential was 1.38 V (vs RHE), which is lower than that of the OER. The AN-1 electrocatalyst showed lower Tafel slope values in both the OER and UOR studies: 173 mV dec−1 and 109mV dec−1, respectively.

CoFe-LDHs were grown on Co-layered hydroxides to achieve 3D-hierarchical flower like architecture for efficient oxygen evolution reaction

In this work, we have successfully synthesized an efficient and cost-effective electrocatalyst for alkaline oxygen evolution (OER) using a solvothermal method combined with an ion exchange strategy. Firstly, single Co-layer hydroxides (Co-LHs) were synthesized by a one-step solvothermal method. Subsequently, [Fe(C2O4)3]3- was introduced onto the Co-LHs surface to facilitate ion exchange, and a further CoFe-layered double hydroxides (CoFe-LDHs) layer was grown on the Co-LHs material surface to finally obtain the nanoflower-like Co-LHs@CoFe-LDHs composite. Related material characterization results showed that C2O42- was successfully inserted into the interlayer structure of the LDHs, resulting in an increase in interlayer spacing. In situ Raman spectroscopy revealed that the active site of the OER reaction in the Co-LHs@CoFe-LDHs material was CoOx. Thanks to the double structure of the LDHs improving charge transfer ability and the synergy between cobalt and iron species, Co-LHs@CoFe-LDHs showed significantly enhanced OER performance. This study provides new insights and methods for the development of novel LDHs structural electrocatalysts.

Macroporous high‐entropy spinel oxide monoliths as efficient oxygen evolution electrocatalyst

AbstractIn this paper, macroporous high‐entropy spinel oxide (HESO) (Fe0.2Ni0.2Co0.2Mn0.2Zn0.2)3O4 monoliths were successfully fabricated via a sol–gel method followed by calcination. Appropriate polyacrylic acid and propylene oxide contents allow the formation of three‐dimensional co‐continuous xerogel monoliths, and the water/glycerol ratio controls the macropore size of monoliths. Subsequent calcination achieves the precipitation of HESO (Fe0.2Ni0.2Co0.2Mn0.2Zn0.2)3O4 with a singular phase and exceptional structural stability. The macroporous HESO (Fe0.2Ni0.2Co0.2Mn0.2Zn0.2)3O4 demonstrates remarkable performance in the oxygen evolution reaction (OER) with an overpotential of 333 mV at 100 mA cm−2 and a Tafel slope of 43.2 mV dec–1, surpassing that of RuO2 (391 mV) under identical conditions. Furthermore, the catalytic stability of the HESO catalyst remains superior even after 24 h of testing. This process offers a promising avenue for the development of macroporous high‐entropy oxide OER catalysts for overall water splitting.

Ag/Nico LDH Heterogeneous Structure for Efficient Alkaline Oxygen Evolution

Hydrogen is regarded as an ideal energy carrier owing to the highest energy density, presenting the possibility of substituting for traditional fossil fuels. Nowadays, water splitting is significant in producing large-scale hydrogen. However, the sluggish reaction kinetics during anodic OER, caused by the four-electron transfer, has hindered this energy conversion strategy. Although IrO2 and RuO2 are currently the representative OER electrocatalysts, their high cost and unsatisfactory performance limit their commercial application.Numerous electrocatalysts, including oxides, hydroxides, high-entropy alloy, metal organic frameworks, and their hybrids, have been developed to address this issue. Among them, layered double hydroxides (LDH) have demonstrated outstanding performance due to their highly adjustable structure, powerful host-guest interaction, and single-atomic-like active sites. NiCo LDH has attracted significant attention because of its appropriate atomic and electronic structure, intrinsic active sites and defects, compared with single-type Ni-based or Co-based catalysts. However, to meet the requirements of industrial production, a simple and scalable method to synthesize electrocatalysts with favorable OER activity and stability is imperative.We propose a facile and scalable strategy to synthesize Ag-decorated NiCo LDH (Ag/NiCo LDH) by electrodeposition and subsequent spontaneous redox reaction. A spontaneous redox reaction driven by the difference in standard redox potential of reactants can be applied to prepare heterogeneous catalysts in consequence of the facile process, tight combination between substrate and decorated materials, and no supplementary energy input. Silver metal, with its appropriate standard redox potential, good conductivity, and low cost compared to Iridium and Ruthenium, serves as a suitable decorated material. This strategy provides several advantages, for example, Ⅰ) optimizing the electronic structure of Ni and Co by the charge transfer from Ni, Co to Ag; Ⅱ) exposing more active surface area because of the heterogeneous structure, Ⅲ) improving the charge transfer capacity owing to the excellent conductivity of Ag nanoparticles, Ⅳ) increasing the stability of NiCo LDH due to the tight combination of Ag and NiCo LDH, Ⅴ) lowering the catalysts' price compared with Iridium and Ruthenium.The synthesized Ag/NiCo LDH exhibits enhanced OER performance in 1M KOH electrolyte, achieving an overpotential of 440 mV at a current density of 1000 mA cm-2 geo, surpassing that of NiCo LDH (722 mV at 1000 mA cm-2 geo). Surprisingly, Ag/NiCo LDH demonstrates exceptional durability, lasting over 425 h at 1000 mA cm-2 geo, an improvement of nearly eight-fold compared to NiCo LDH (50 h). This study provides a promising approach for developing efficient and stable electrocatalysts for alkaline oxygen evolution.

Superhydrophilic cobalt-doped NiFe LDH graphite felt with enriched oxygen vacancy as an efficient oxygen evolution electrocatalyst in alkaline media

Efficient non-precious metal electrocatalysts are crucial for hydrogen production through water electrolysis. Combining a superhydrophilic electrocatalyst with oxygen vacancy and a conductive carbon matrix is significant for NiFe LDH-based oxygen evolution reaction (OER) applications. In this study, NiFe LDH nanoflowers and Co-doped NiFe LDH nanoneedles were synthesized on graphite felt through an in-situ self-assembly strategy. Further results have shown that doping Co into NiFe LDH nanoarrays significantly enhances the specific surface area and oxygen vacancy density, while the graphite felt serves as a conductive scaffold and prevents active sites detachment. Oxygen vacancies in Co3–Ni7Fe3 LDH/TGF adjust the electronic configuration, and superhydrophilicity promotes effective electrolyte diffusion. This synergy endows Co3–Ni7Fe3 LDH/TGF with excellent OER performance, lower overpotential of 252 mV (10 mA cm−2), a Tafel slope (63.13 mV), and stability at high current densities. This research provides a new perspective for utilizing non-precious metal catalysts on carbon substrates for hydrogen production.

Charge engineering in black phosphorene with tunable electronic structures as efficient oxygen evolution electrocatalyst

The unique electronic structure of layered black phosphorus (BP) makes it an ideal candidate material for electrocatalytic oxygen evolution reaction (OER). Charge doping effectively improves the environmental stability and catalytic activity of BP by providing electron transfer channels and reducing charge transfer barrier. Therefore, based on the first principles calculation, this paper theoretically discusses how the intrinsic charge doping without introducing impurities changes the electronic structure and improves the catalytic activity of BP. It is found that charge engineering can effectively regulate and change the electronic structure and work function by stimulating the hybridization between different P-p orbitals, while maintaining the direct bandgap semiconductor characteristics of monolayer BP system. More importantly, in the catalytic process of OER, electrons and hole doping as free charges provide different donor and acceptor energy levels for the system depending on the doping concentration, and affect the adsorption capacity of monolayer BP to different reaction intermediates. At a certain doping concentration, the carrier mobility increases significantly, and the optimal Gibbs free energy and overpotential can be achieved in monolayer BP. These results provide new opportunities and possibilities for designing charge-engineered BP catalysts with adjustable electronic structure and excellent OER activity.

CoFe(OH)x-Co3O4/NF as highly efficient electrocatalyst for oxygen evolution and urea oxidation reactions at high current densities

The advancement of an affordable and highly effective catalyst for the oxygen evolution reaction (OER) is essential to enhance the performance of overall water splitting (OWS). Here, we report a highly efficient nickel foam (NF)-supported CoFe(OH)x-Co3O4/NF heterostructure catalyst for OER. The CoFe(OH)x-Co3O4/NF heterostructure catalyst contain amorphous phase CoFe(OH)x and crystalline Co3O4, and the synergistic interaction between the two different phases reduces the charge transfer resistance, accelerates the kinetic processes of electrocatalysis and makes the catalysts exhibit excellent catalytic performance. In 1.0 M KOH solution, an overpotential (η) of merely 262 mV is needed to attain a current density of 100 mA cm−2. Even at high current densities demanded for commercial applications, the overpotentials remain very low (η500 = 291 mV, η1000 = 319 mV). The catalytic activity of CoFe(OH)x-Co3O4/NF has exceeded that of most non-noble metal OER catalysts documented in the literature. Furthermore, the CoFe(OH)x-Co3O4/NF catalyst demonstrates superior catalytic stability to OER, with only a 23 mV potential increase after 24 h of stability testing at a high current density of 500 mA cm−2. Owing to the heterostructure, the CoFe(OH)x-Co3O4/NF catalyst also exhibits excellent catalytic performance for the urea oxidation reaction (UOR), and the use of UOR instead of OER at the anode of OWS significantly reduces the cell voltage, thereby reducing the electrolytic energy consumption. The findings in this work offer precious insights into the design of OWS anode catalysts and their important applications in industrial water electrolysis. These insights are crucial for advancing the development of highly efficient and sustainable water electrolysis processes, which is essential for the production of green hydrogen and other valuable chemicals.

Performance of Co9S8/Cu2S@LDH nanowires prepared by dual sulfur sources to promote oxygen evolution performance

Hydrogen production through water electrolysis is an effective method for obtaining clean energy. The oxygen evolution reaction plays a key role in the process of water electrolysis, and the development of efficient and stable oxygen evolution electrocatalysts is crucial to improve the efficiency of hydrogen production. This paper presents the preparation of Co9S8/Cu2S@LDH nanowire catalysts on copper foam using thiourea and sodium sulfide as dual sulfur sources by a hydrothermal method combined with electrochemical deposition. The composition, structure, and performance of the catalysts were investigated using characterization methods of XRD, SEM, Raman, and electrochemical analyses. Also, the mechanism of thiourea's role in the process of sulfurization of dual sulfur sources was also revealed. The results indicate that the introduction of thiourea facilitates the generation of the active center CoOOH and improves the catalytic efficiency of oxygen precipitation with a low overpotential of 199 mV at 10 mA/cm2 in 1.0 M KOH electrolyte. Additionally, the LDH deposited in the outer layer effectively prevents the oxidation of Co9S8/Cu2S and improves the catalyst's stability. Therefore, the prepared Co9S8/Cu2S@LDH nanowire catalyst exhibits high oxygen evolution reaction (OER) catalytic activity and stability in alkaline electrolyte, making it a promising OER catalyst.

Exploring Cu-Doped Co3O4 Bifunctional Oxygen Electrocatalysts for Aqueous Zn-Air Batteries.

The efficiency of oxygen electrocatalysis is a key factor in diverse energy domain applications, including the performance of metal-air batteries, such as aqueous Zinc (Zn)-air batteries. We demonstrate here that the doping of cobalt oxide with optimal amounts of copper (abbreviated as Cu-doped Co3O4) results in a stable and efficient bifunctional electrocatalyst for oxygen reduction (ORR) and evolution (OER) reactions in aqueous Zn-air batteries. At high Cu-doping concentrations (≥5%), phase segregation occurs with the simultaneous presence of Co3O4 and copper oxide (CuO). At Cu-doping concentrations ≤5%, the Cu ion resides in the octahedral (Oh) site of Co3O4, as revealed by X-ray diffraction (XRD)/Raman spectroscopy investigations and molecular dynamics (MD) calculations. The residence of Cu@Oh sites leads to an increased concentration of surface Co3+-ions (at catalytically active planes) and oxygen vacancies, which is beneficial for the OER. Temperature-dependent magnetization measurements reveal favorable d-orbital configuration (high eg occupancy ≈ 1) and a low → high spin-state transition of the Co3+-ions, which are beneficial for the ORR in the alkaline medium. The influence of Cu-doping on the ORR activity of Co3O4 is additionally accounted in DFT calculations via interactions between solvent water molecules and oxygen vacancies. The application of the bifunctional Cu-doped (≤5%) Co3O4 electrocatalyst resulted in an aqueous Zn-air battery with promising power density (=84 mW/cm2), stable cyclability (over 210 cycles), and low charge/discharge overpotential (=0.92 V).

Cobalt molybdenum di-selenide surface modification: A path to improved trifunctional catalysis via partial oxygenation

Efficient, stable, and cost-effective electrocatalysts for hydrogen evolution, oxygen evolution, and oxygen reduction reactions have been in demand for decades. Recently, layered transition metals (Co, Mo, Ni, and Fe) and chalcogen compounds (S/Se/Te) gained prominence in catalysis and device studies. Density functional theory identified the covalency of Co and Mo, oxygenated bimetallic selenium bond, crystal structure distortions, and adsorption properties as crucial for enhanced electrocatalytic activity. Hybridizing the Co and Mo d-orbitals around the Fermi level of 0.463 eV improves bonding with metal surface-adsorbate intermediates validated by partial density of states. Oxygenated cobalt molybdenum selenide (O-CoMoSe2) (210) exhibited remarkable electrocatalytic properties at various active sites, with Gibbs free energy and theoretical overpotential at an active site of Co = 0.086 eV, 0.41 V, and Se = 0.50 V.

NiCo2O4/MXene Hybrid as an Efficient Bifunctional Electrocatalyst for Oxygen Evolution and Reduction Reaction

AbstractFor the advancement of electrochemical energy conversion and storage technologies, bifunctional electrocatalysts are crucial for efficiently driving both the oxygen evolution (OER) and reduction reactions (ORR). Cobalt‐based spinel oxides are a class of promising bifunctional electrocatalysts. However their low electrical conductivity and stability may hinder further improvement. A novel composite material composed of NiCo2O4 nanoparticles integrated with emerging two dimensional MXene nanosheets (NiCo2O4/MXene) was developed. The successful integration of NiCo2O4 with MXene brings about a number of attractive structural features. This includes synergistic effects between NiCo2O4 and MXene, highly accessible surface areas, complete exposure of numerous active sites, and excellent electronic conductivity, all of which collectively contribute to the desirability of composite material for OER and ORR. The synthesized NiCo2O4/MXene composite showed extraordinary OER electrocatalytic activity with a lower overpotential of 360 mV at a current density of 10 mA/cm2, and a small Tafel slope of 64 mV/dec compared to NiCo2O4, MXene and NiCo2O4+MXene (physically mixed). Additionally, NiCo2O4/MXene displays an ORR limiting current density of −4 mA/cm2 and exhibited highest onset potential and half wave potential of 0.92 V and 0.72 V vs. RHE, respectively, for the ORR in alkaline media compared to NiCo2O4, MXene and NiCo2O4+MXene (physically mixed).

Regulating the Electronic Structure of Metal-Organic Frameworks by Introducing Mn for Enhanced Oxygen Evolution Activity.

The construction of low-cost and highly efficient oxygen evolution electrocatalysts is paramount for clean and sustainable hydrogen energy. In recent years, metal-organic framework (MOF) OER electrocatalysts have attracted tremendous research attention. Herein, we report a simple and facile strategy to construct bimetallic MOFs (named CoMn0.01) for enhancing OER catalytic performance. Significantly, CoMn0.01 exhibited remarkable OER activity (255 mV at 10 mA cm-2) and a low Tafel slope of 66 mV dec-1, superior to those of commercial benchmark electrocatalysts (RuO2, 352 mV, 178 mV dec-1). Besides, the catalyst demonstrated outstanding longevity for 144 h at a current density of 100 mA cm -2. Mn doping can regulate the electronic structure of Co MOFs, which optimizes charge transfer capability and improves conductivity.

Modulating positive charge sites generations and iron oxidation state transitions in FeP4/CoP/C p-n heterojunction toward efficient oxygen evolution

Promoting the formation of positive charge active sites and high oxidation state FeOOH in the heterojunction electrocatalyst can enhance its intrinsic activity for oxygen evolution reaction (OER). However, the current synthesis methods that can simultaneously achieve both properties remain a great challenge. In this work, a feasible strategy for concurrently promoting the generation of positive charge active sites and high oxidation state metal species by constructing a heterojunction between FeP4 and CoP is proposed. Specifically, the p-n heterojunction between FeP4 and CoP is constructed by pyrolysis of MIL88A@FeCoLDH prepared by introducing Co through cation exchange using MIL88A as a template. The experimental and density functional theory calculation analyses suggest the construction of p-n heterojunction can effectively modulate the electron structure, optimize the d-band center, induce the generation of strong space charge region, and shorten the bond length of Fe-O, thus promoting the formation of positive charge active sites and high active species FeOOH and the adsorption ability of oxygen-containing intermediates for enhancing the OER performance. Benefiting from the synergistic effect between positive charge active sites and FeOOH, the obtained FeP4/CoP/C electrocatalyst exhibits a low overpotential of 258 mV for the OER at a current density of 10 mA cm−2 and superior stability at 20 mA cm−2 for 52 h. This work gives insights into the charge regulation effect in the heterojunction for enhancing the OER catalytic activity and provides a general strategy for designing more efficient oxygen evolution electrocatalysts.

Ce doped Ni(OH)2/Ni-MOF nanosheets as an efficient oxygen evolution and urea oxidation reactions electrocatalyst

Metal-organic frameworks (MOFs) are widely recognized as precursors or sacrificial templates for the synthesis of target catalysts on account of their high porosity and high active surface area. Elemental doping strategy is considered as an effective method for the synthesis of efficient and stable catalysts for electrolytic water. Therefore, in this paper, Ce-doped Ni(OH)2 nanoparticles and Ni-MOF nanosheets composites were synthesized by electrodeposition using Ni-MOF as precursor. Catalyst Ce–Ni(OH)2@Ni-MOF/NF displays excellent OER performance, requiring only 193 mV and 279 mV overpotentials to realize current densities of 10 mA cm−2 and 100 mA cm−2, respectively, while the UOR performance was very remarkable, only a potential of 1.28 V was demanded to reach a current density of 10 mA cm−2. In addition, no obvious change in the overpotential was noticed during the stability test of 16 h, indicating good stability of Ce–Ni(OH)2@Ni-MOF/NF. This study provides a meaningful reference for the design of an efficient and stable environmental friendly electrocatalyst.

Optimizing Edge Active Sites via Intrinsic In-Plane Iridium Deficiency in Layered Iridium Oxides for Oxygen Evolution Electrocatalysis.

Improving catalytic activity of surface iridium sites without compromising catalytic stability is the core task of designing more efficient electrocatalysts for oxygen evolution reaction (OER) in acid. This work presents phase transition of a bulk layered iridate Na2IrO3 in acid solution at room temperature, and subsequent exfoliation to produce 2D iridium oxide nanosheets with around 4nm thickness. The nanosheets consist of OH-terminated, honeycomb-type layers of edge-sharing IrO6 octahedral framework with intrinsic in-plane iridium deficiency. The nanosheet material is among the most active Ir-based catalysts reported for acidic OER and gives an iridium mass activity improvement up to a factor of 16.5 over rutile IrO2 nanoparticles. The material also exhibits good catalytic and structural stability and retains the catalytic activity for more than 1300 h. The combined experimental and theoretical results demonstrate that edge Ir sites of the layer are active centers for OER, with structural hydroxyl groups participating in the catalytic cycle of OER via a non-traditional adsorbate evolution mechanism. The existence of intrinsic in-plane iridium deficiency is the key to building a unique local environment of edge active sites that have optimal surface oxygen adsorption properties and thereby high catalytic activity.

A Self-Supporting Electrode Material (NiS/NF) as a Stable and Efficient Electrocatalyst for Oxygen Evolution: In Situ Surface Activation of Nickel Sulfide to Nickel Oxide/(Oxy)hydroxide

A Self-Supporting Electrode Material (NiS/NF) as a Stable and Efficient Electrocatalyst for Oxygen Evolution: <i>In Situ</i> Surface Activation of Nickel Sulfide to Nickel Oxide/(Oxy)hydroxide

Biological upcycling of nickel and sulfate as electrocatalyst from electroplating wastewater

Upcycling nickel (Ni) to useful catalyst is an appealing route to realize low-carbon treatment of electroplating wastewater and simultaneously recovering Ni resource, but has been restricted by the needs for costly membranes or consumption of large amount of chemicals in the existing upcycling processes. Herein, a biological upcycling route for synchronous recovery of Ni and sulfate as electrocatalysts, with certain amount of ferric salt (Fe3+) added to tune the product composition, is proposed. Efficient biosynthesis of bio-NiFeS nanoparticles from electroplating wastewater was achieved by harnessing the sulfate reduction and metal detoxification ability of Desulfovibrio vulgaris. The optimal bio-NiFeS, after further annealing at 300 °C, served as an efficient oxygen evolution electrocatalyst, achieving a current density of 10 mA·cm−1 at an overpotential of 247 mV and a Tafel slope of 60.2 mV·dec−1. It exhibited comparable electrocatalytic activity with the chemically-synthesized counterparts and outperformed the commercial RuO2. The feasibility of the biological upcycling approach for treating real Ni-containing electroplating wastewater was also demonstrated, achieving 99.5 % Ni2+removal and 41.0 % SO42− removal and enabling low-cost fabrication of electrocatalyst. Our work paves a new path for sustainable treatment of Ni-containing wastewater and may inspire technology innovations in recycling/ removal of various metal ions.

A highly efficient and long-term durable electrocatalyst for oxygen evolution in alkaline seawater by growing Ni1.5Fe1.5B on the NiMoO4 nanorods

The development of efficient and stable catalysts for the oxygen evolution reaction (OER) that can function effectively in seawater is crucial for addressing the energy crisis. In this study, a low-cost hydrothermal-dip-coating method was employed to synthesize Ni1.5Fe1.5B nanosheets decorated three-dimensional NiMoO4 nanorods anchored on nickel foam (NiMoO4@Ni1.5Fe1.5B). This catalyst exhibits high conductivity and electrochemically active surface areas, which can be attributed to the synergistic effect between NiMoO4 and Ni1.5Fe1.5B, the presence of numerous oxygen vacancies, and the modification of boron. The NiMoO4@Ni1.5Fe1.5B catalyst exhibits exceptional catalytic activity for the oxygen evolution reaction (OER), as evidenced by overpotentials of 235 and 262 mV required to achieve current densities of 100 and 200 mA cm−2, respectively, in 1 M KOH. Notably, the leaching of Mo during the OER in alkaline conditions contributes to the preservation of the 3D core-shell structure of NiMoO4@Ni1.5Fe1.5B, resulting in improved stability and resistance to chloride-induced corrosion. In seawater with a concentration of 1 M KOH, the catalyst requires overpotentials of 261 and 299 mV to achieve current densities of 100 and 200 mA cm−2, respectively, and can operate continuously for 72 h without significant performance degradation.