Synthesis of Ni/NiO@MoO_3−x Composite Nanoarrays for High Current Density Hydrogen Evolution Reaction

High current density hydrogen evolution reaction (HER) in alkaline water electrolysis plays crucial role in renewable and sustainable energy systems, while posing a great challenge to the highly-efficient electrocatalysts. Here, the synthesis of Ni/NiO@MoO_3−x composite nanoarrays is reported by a moderate reduction strategy, combining Ni/NiO nanoparticles (≈20 nm) with amorphous MoO_3−x nanoarrays. The Ni/NiO@MoO_3−x composite nanoarrays possess enhanced hydrophilicity, optimize reaction energy barriers, accelerate reactant diffusion/bubble detachment, and therefore display an ultrahigh alkaline HER activity with a low η₁₀ overpotential of 7 mV as well as Tafel slope of 34 mV dec⁻¹. More significantly, the Ni/NiO@MoO_3−x nanoarrays only demand low overpotentials of 75 and 112 mV to deliver 100 and 200 mA cm⁻² hydrogen production current, and can steadily work at 100 mA cm⁻² for 40 h, which is more efficient and stable than the Pt/C catalyst.