In situ Mo-leaching constructs Ni-Co hydroxide solid solution nanorods for synergistic alkaline hydrogen evolution

Developing efficient electrocatalysts for the alkaline hydrogen evolution reaction (HER) remains challenging due to sluggish water dissociation and suboptimal hydrogen adsorption. Herein, we report an in-situ precursor-leaching-induced strategy for fabricating Co x Ni 1-x (OH) 2 solid solution nanorod arrays via complete Mo leaching from hydrothermally grown Co x Ni 1-x MoO 4 ·H 2 O on Ni-Co foam. This transformation preserves the one-dimensional architecture, yielding a Mo-free, binder-free electrode with exceptional HER activity, characterized by overpotentials of 38 mV and 208 mV at 10 and 50 mA cm -2 , respectively, and stability over 300 h at 100 mA cm -2 . Experimental and theoretical analyses reveal that adjacent Ni and Co sites synergistically optimize the adsorption thermodynamics of hydrogen intermediates and promote interfacial charge transfer, while Mo is fully removed as a sacrificial component that triggers the in-situ reconstruction into a Co–Ni hydroxide solid solution. This work provides a practical route to high-performance alkaline HER catalysts enabled by atomic-level Ni–Co electronic synergy.