Facile electrochemical synthesis of Ni-Co-B film on Cu sheet for dual-electrocatalysis of hydrogen and oxygen evolution reactions

Engineering superhydrophilic Ni-Se-P on Ni-Co nanosheets-nanocones arrays for enhanced hydrogen production assisted by hydrazine oxidation reaction

The production of hydrogen gas as an environmentally friendly and emission-free fuel source, has emerged as the preeminent substitute for traditional fossil fuels. The demand for a viable and low-cost substitute of the anodic Oxygen Evolution Reaction (OER) in hydrogen gas production has led researchers to explore the Hydrazine Oxidation Reaction (HzOR), aiming to reduce overpotential. In this study, we present the synthesis of a NiSeP@NiCo/Cu electrocatalyst via electrodeposition method, offering precise control over parameter adjustments and an affordable price. The binder-free nanosheet structure of this electrocatalyst demonstrates improved performance in water electrolysis, resulting in potentials of -40 and -134 mV vs. Reversible Hydrogen Electrode (RHE) for Hydrogen Evolution Reaction (HER) and 0.041 and 0.194 V (vs. RHE) for HzOR (i = 10 and 100 mA.cm-2). The electrode has excellent features, including active electrochemical surface, synergistic effects among the elements, high stability, super-hydrophilicity and super-aerophobicity. The Bi-functional performance of electrode was tested in a two-electrode set for HER/HzOR, the cell voltage required to reach current densities of 10 and 100 mA.cm-2 were determined as 0.071 and 0.298 V respectively. On the whole, this work presents the excellent capabilities of the synthesized electrode (NiSeP@NiCo/Cu) for hydrogen gas production.

In Situ Construction of Biphasic Boride Electrocatalysts on Dealloyed Bulk Ni-Mo Alloy as Self-Supporting Electrode for Water Splitting at High Current Density

Nickel-molybdenum-boron (Ni-Mo-B)-based catalysts with biphasic interfaces are highly advantageous in bifunctional electrocatalytic activity in alkaline water-splitting. However, it remains an ongoing challenge to obtain porous Ni-Mo alloy substrates that provide stable adhesion to catalysts, ensuring the long-term performance of bifunctional self-supporting electrodes at a high current density. Herein, a porous Ni-Mo alloy substrate was effectively obtained by a cost-effective dealloying process on a commercial Ni-Mo alloy with high-energy crystal planes. Subsequently, the Mo2NiB2/Ni3B bifunctional catalyst was in situ synthesized on this substrate via boriding heat treatment, resulting in outstanding catalytic activity and stability. Density functional theory (DFT) calculations reveal that the abundant biphasic interfaces and surface-reconstructed sites of the Mo2NiB2/Ni3B catalyst can decrease the energy barriers for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Thus, the designed self-supporting electrodes show bifunctional catalytic activity with overpotentials of 151 mV for HER and 260 mV for OER at a current density of 10 mA cm-2. Markedly, the assembled water electrolyzer can be driven up to 10 mA cm-2 at 1.64 V and maintain catalytic activity at a high current density of 1000 mA cm-2 for 100 h. The new strategy is expected to provide a low-cost scheme for designing self-supporting bifunctional electrodes with high activity and excellent stability and contribute to the development of hydrogen energy technology.

A Review of Transition Metal Boride, Carbide, Pnictide, and Chalcogenide Water Oxidation Electrocatalysts

Transition metal borides, carbides, pnictides, and chalcogenides (X-ides) have emerged as a class of materials for the oxygen evolution reaction (OER). Because of their high earth abundance, electrical conductivity, and OER performance, these electrocatalysts have the potential to enable the practical application of green energy conversion and storage. Under OER potentials, X-ide electrocatalysts demonstrate various degrees of oxidation resistance due to their differences in chemical composition, crystal structure, and morphology. Depending on their resistance to oxidation, these catalysts will fall into one of three post-OER electrocatalyst categories: fully oxidized oxide/(oxy)hydroxide material, partially oxidized core@shell structure, and unoxidized material. In the past ten years (from 2013 to 2022), over 890 peer-reviewed research papers have focused on X-ide OER electrocatalysts. Previous review papers have provided limited conclusions and have omitted the significance of "catalytically active sites/species/phases" in X-ide OER electrocatalysts. In this review, a comprehensive summary of (i) experimental parameters (e.g., substrates, electrocatalyst loading amounts, geometric overpotentials, Tafel slopes, etc.) and (ii) electrochemical stability tests and post-analyses in X-ide OER electrocatalyst publications from 2013 to 2022 is provided. Both mono and polyanion X-ides are discussed and classified with respect to their material transformation during the OER. Special analytical techniques employed to study X-ide reconstruction are also evaluated. Additionally, future challenges and questions yet to be answered are provided in each section. This review aims to provide researchers with a toolkit to approach X-ide OER electrocatalyst research and to showcase necessary avenues for future investigation.

Hexagonal NiMoO4-MoS2 nanosheet heterostructure as a bifunctional electrocatalyst for urea oxidation assisted overall water electrolysis

A hexagonal NiMoO4-MoS2 nanosheet heterostructure on nickel foam (NiMoO4-MoS2/NF) was synthesized by simple hydrothermal and annealing treatment.