FeCoNi Sulfides Derived From In situ Sulfurization of Precursor Oxides as Oxygen Evolution Reaction Catalyst

Enhancing photocatalytic reduction of Cr(VI) in water through morphological manipulation of g-C3N4 photocatalysts: A comparative study of 1D, 2D, and 3D structures

In this research, the dimensional catalysts of pure g-C3N4 photocatalysts (1D, 2D, and 3D) were investigated for the reduction of the highly toxic/carcinogenic Cr(VI) under visible light irradiation. The catalysts underwent explanation through various surface analysis techniques. According to the BET data, the specific surface area of the 3D catalyst was 1.3 and 7 times higher than those of the 2D and 1D CN catalysts, respectively. The 3D catalyst demonstrated superior performance, achieving an efficiency greater than 99% within 60 min under visible light irradiation in the presence of EDTA due to the abundance of active sites. The study also delved into the influence of factors such as the amount of EDTA-hole scavenger, pH, catalyst dosage, and temperature on the photocatalytic reduction of Cr(VI). Moreover, the 3D catalyst showed excellent reusability, maintaining an efficiency of more than 80% even after 10 cycles, and performed effectively in real water samples. The 3D CN catalyst, with its facile synthesis process, excellent visible light harvesting properties, high reduction efficiency that sustains over multiple cycles, and outstanding performance in real water samples, presents a significant advancement for practical applications in environmental remediation. This research contributes to a new understanding of developing efficient degradation methods for heavy metals in polluted water, highlighting the potential of 3D g-C3N4 catalysts in environmental cleanup efforts.

Incorporation of Ag in Co9S8-Ni3S2 for Predominantly Enhanced Electrocatalytic Activities for Oxygen Evolution Reaction: A Combined Experimental and DFT Study

Electrodeposition of abundant metals to fabricate efficient and durable electrodes indicate a viable role in advancing renewable electrochemical energy tools. Herein, we deposit Co9S8-Ag-Ni3S2@NF on nickel foam (NF) to produce Co9S8-Ag-Ni3S2@NF as a exceedingly proficient electrode for oxygen evolution reaction (OER). The electrochemical investigation verifies that the Co9S8-Ag-Ni3S2@NF electrode reveals better electrocatalytic activity to OER because of its nanoflowers' open-pore morphology, reduced overpotential (η10=125 mV), smaller charge transfer resistance, long-term stability, and a synergistic effect between various components, which allows the reactants to be more easily absorbed and subsequently converted into gaseous products during the water electrolysis route. Density functional theory (DFT) calculation as well reveals the introduction of Ag (222) surface into the Co9S8 (440)-Ni3S2 (120) structure increases the electronic density of states (DOS) per unit cell of a system and increases the electrocatalytic activity of OER by considerably lowering the energy barriers of its intermediates. This study provides the innovation of employing trimetallic nanomaterials immobilized on a conductive, continuous porous three-dimensional network formed on a nickel foam (NF) substrate as a highly proficient catalyst for OER.

CoFeBP Micro Flowers (MFs) for Highly Efficient Hydrogen Evolution Reaction and Oxygen Evolution Reaction Electrocatalysts

Hydrogen is one of the most promising green energy alternatives due to its high gravimetric energy density, zero-carbon emissions, and other advantages. In this work, a CoFeBP micro-flower (MF) electrocatalyst is fabricated as an advanced water-splitting electrocatalyst by a hydrothermal approach for hydrogen production with the highly efficient hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The fabrication process of the CoFeBP MF electrocatalyst is systematically optimized by thorough investigations on various hydrothermal synthesis and post-annealing parameters. The best optimized CoFeBP MF electrode demonstrates HER/OER overpotentials of 20 mV and 219 mV at 20 mA/cm2. The CoFeBP MFs also exhibit a low 2-electrode (2-E) cell voltage of 1.60 V at 50 mA/cm2, which is comparable to the benchmark electrodes of Pt/C and RuO2. The CoFeBP MFs demonstrate excellent 2-E stability of over 100 h operation under harsh industrial operational conditions at 60 °C in 6 M KOH at a high current density of 1000 mA/cm2. The flower-like morphology can offer a largely increased electrochemical active surface area (ECSA), and systematic post-annealing can lead to improved crystallinity in CoFeBP MFs.

Perovskite-based electrocatalysts for oxygen evolution reaction in alkaline media: A mini review

Water electrolysis is one of the attractive technologies for producing clean and sustainable hydrogen fuels with high purity. Among the various kinds of water electrolysis systems, anion exchange membrane water electrolysis has received much attention by combining the advantages of alkaline water electrolysis and proton exchange membrane water electrolysis. However, the sluggish kinetics of the oxygen evolution reaction, which is based on multiple and complex reaction mechanisms, is regarded as a major obstacle for the development of high-efficiency water electrolysis. Therefore, the development of high-performance oxygen evolution reaction electrocatalysts is a prerequisite for the commercialization and wide application of water electrolysis systems. This mini review highlights the current progress of representative oxygen evolution reaction electrocatalysts that are based on a perovskite structure in alkaline media. We first summarize the research status of various kinds of perovskite-based oxygen evolution reaction electrocatalysts, reaction mechanisms and activity descriptors. Finally, the challenges facing the development of perovskite-based oxygen evolution reaction electrocatalysts and a perspective on their future are discussed.

Controllable and Scale-Up Synthesis of Nickel-Cobalt Boride@Borate/RGO Nanoflakes via Reactive Impingement Mixing: A High-Performance Supercapacitor Electrode and Electrocatalyst

Large-scale synthesis of graphene-based nanomaterials in stirred tank reactor (STR) often results in serious agglomeration because of the poor control during micromixing process. In this work, reactive impingement mixing is conducted in a two-stage impinging jet microreactor (TS-IJMR) for the controllable and scale-up synthesis of nickel-cobalt boride@borate core-shell nanostructures on RGO flakes (NCBO/RGO). Benefiting from the good process control and improved micromixing efficiency of TS-IJMR, NCBO/RGO nanosheet provides a large BET surface area, abundant of suitable mesopores (2–5 nm), fast ion diffusion, and facile electron transfer within the whole electrode. Therefore, NCBO/RGO electrode exhibits a high specific capacitance of 2383 F g−1 at 1 A g−1, and still retains 1650 F g−1 when the current density is increased to 20 A g−1, much higher than those of nickel boride@borate/RGO (NBO/RGO) and cobalt boride@borate/RGO (CBO/RGO) synthesized in TS-IJMR, as well as NCBO/RGO-S synthesized in STR. In addition, an asymmetric supercapacitor (NCBO/RGO//AC) is constructed with NCBO/RGO and activated carbon (AC), which displays a high energy density of 53.3 W h kg−1 and long cyclic lifespan with 91.8% capacitance retention after 5000 charge-discharge cycles. Finally, NCBO/RGO is used as OER electrocatalyst to possess a low overpotential of 309 mV at a current density of 10 mA cm−2 and delivers a good long-term durability for 10 h. This study opens up the potential of controllable and scale-up synthesis of NCBO/RGO nanosheets for high-performance supercapacitor electrode materials and OER catalysts.

Sulfur Vacancies-Engineered Ni3 S4-x Hollow Microspheres with Optimized Anionic Adsorption Energy for High-Performance Supercapacitor

Nickel sulfides with high theoretical capacitance have aroused tremendous attention for next-generation supercapacitors. Unfortunately, the structural durability of nickel sulfides is insufficient to support the long-term working situation. Herein, Ni₃ S_4-x hollow microspheres with sulfur vacancies (Ni₃ S_4-x HMs) are constructed by a liquid-phase anion exchange process using the Ni-MOF as the precursor. Both experimental investigation and theoretical analysis suggest that the deliberately introduced sulfur vacancies effectively improve the anionic adsorptive ability of nickel sulfides in the KOH electrolyte, significantly enhancing the reversible capacitance and structural durability (1884 F g^-1 at 2 A g^-1 , capacity retention of 97.9% after 10 000 cycles). In addition, an asymmetrical solid-state supercapacitor consisting of Ni₃ S_4-x HMs cathode and activated carbon anode shows infusive energy/power density (33.05 Wh kg^-1 /1.68 kW kg^-1 ) and remains 82.4% over 10 000 repeated charging/discharging processes in the KOH-PVA gel electrolyte. The strategies can be developed to enlighten the structural design of various metal sulfides materials adopted in electrochemical energy storage devices including alkali ion batteries, supercapacitors, and electrocatalysts.

Perovskite With Tunable Active-Sites Oxidation State by High-Valence W for Enhanced Oxygen Evolution Reaction

Perovskite oxides have been established as a promising kind of catalyst for alkaline oxygen evolution reactions (OER), because of their regulated non-precious metal components. However, the surface lattice is amorphous during the reaction, which gradually decreases the intrinsic activity and stability of catalysts. Herein, the precisely control tungsten atoms substituted perovskite oxides (Pr_0.5Ba_0.5Co_1-xW_xO₃-_δ) nanowires were developed by electrostatic spinning. The activity and Tafel slope were both dependent on the W content in a volcano-like fashion, and the optimized Pr_0.5Ba_0.5Co_0.8W_0.2O₃-_δ exhibits both excellent activity and superior stability compared with other reported perovskite oxides. Due to the outermost vacant orbitals of W⁶⁺, the electronic structure of cobalt sites could be efficiently optimized. Meanwhile, the stronger W-O bond could also significantly improve the stability of latticed oxide atoms to impede the generation of surface amorphous layers, which shows good application value in alkaline water splitting.