Preparation of highly active MoNi4 alloys in 3D porous nanostructures and their application as bifunctional electrocatalysts for overall water splitting

Precise modulation of nickel-molybdenum alloy (MoNi4)/molybdenum dioxide nanowires via a ternary nickel-cobalt-iron complex for enhanced electrochemical overall water splitting

Developing renewable and clean energy technologies necessitates the design of efficient bifunctional catalysts that can facilitate electrochemical water splitting without relying on inert metals. This study presents a novel three-step strategy for fabricating nickel cobalt iron (NiCoFe)-modified nickel-molybdenum alloy/molybdenum dioxide (MoNi4/MoO2) nanowires on nickel foam (NF) substrates, denoted as NiCoFe-MoNi4/MoO2/NF. The synthesized catalyst demonstrates exceptional performance, achieving an impressively low overpotential (13 mV) at 10 mA·cm-2 current density for the hydrogen evolution reaction (HER) and 230 mV at 50 mA·cm-2 for the oxygen evolution reaction (OER). Its performance surpasses many noble-metal catalysts, achieving overall water splitting at just 1.51 V under 50 mA·cm-2. The distinctive one-dimensional (1D) nanostructure and synergistic interplay between the NiCoFe complex and the MoNi4/MoO2 framework enhance mass transfer, expose additional active sites, and enhance intrinsic activity, contributing to outstanding efficiency. Incorporating cobalt (Co) and iron (Fe) into the ternary complex greatly improved the efficiencies of both HER and OER, providing a promising approach for developing high-performance, cost-effective bifunctional electrocatalysts and promoting advancements in sustainable energy conversion technologies.

NiCu alloys anchored Co3O4 nanowire arrays as efficient hydrogen evolution electrocatalysts in alkaline and neutral media

Robust and long-lasting non-precious metal electrocatalysts are essential to achieve sustainable hydrogen production. In this work, we synthesized Co₃O₄@NiCu by electrodepositing NiCu nanoclusters onto Co₃O₄ nanowire arrays that were formed in situ on nickel foam. The introduction of NiCu nanoclusters altered the inherent electronic structure of Co₃O₄, significantly increasing the exposure of active sites and enhancing endogenous electrocatalytic activity. Co₃O₄@NiCu exhibited overpotentials of only 20 and 73 mV, respectively, at 10 mA cm^-2 current densities in alkaline and neutral media. These values were equivalent to those of commercial Pt catalysts. Finally, the electron accumulation effect at the Co₃O₄@NiCu, along with a negative shift in the d-band center, is finally revealed by theoretical calculations. Hydrogen adsorption on consequent electron-rich Cu sites was effectively weakened, leading to a robust catalytic activity for the hydrogen evolution reaction (HER). Overall, this study proposes a practical strategy for creating efficient HER electrocatalysts in both alkaline and neutral media.