Electrodeposited crystalline-amorphous Ni-Ni(OH)2 electrocatalysts for efficient hydrogen evolution via alkaline water splitting

Transition metal electrocatalysts with crystalline-amorphous heterostructures have garnered particular attention owing to the pronounced synergistic effect between a crystalline phase with high electrical conductivity and an amorphous phase with abundant catalytic active sites. Herein, we construct crystalline-amorphous Ni-Ni(OH)2 hybrids via a facile electrodeposition approach for efficient alkaline hydrogen evolution reaction (HER). The Ni-Ni(OH)2 heterostructures are directly electrodeposited on the surface of Cu nanowires (NWs) in-situ grown on Cu foam with a well-maintained nanowire morphology. The Cu NWs on Cu foam substrate provide a three-dimensional structure, and enable efficient electron transportation to the Ni-Ni(OH)2 sites. Moreover, in the crystalline-amorphous Ni-Ni(OH)2 heterostructures, amorphous Ni(OH)2 nanosheets accelerate the water dissociation, while crystalline Ni active sites promote the formation and combination of adsorbed hydrogen atoms. Such a promising synergistic effect leads to the enhanced HER performance with low overpotentials of 73 and 336 mV at the current densities of 10 and 100 mA cm−2, respectively, and a small Tafel slope of 33 mV dec−1. In addition, the integrated structure enables the Ni-Ni(OH)2 electrode with a durable stability of 35 mA cm−2 for 100 h. This work offers an effective approach to construct crystalline-amorphous materials for efficient alkaline HER.