Heterogeneous interface engineered atomic configuration on ultrathin Ni(OH)2/Ni3S2 nanoforests for efficient water splitting

The sluggish water dissociation kinetics of low-cost Ni3S2 electrocatalysts severely hinders the hydrogen evolution reaction (HER), resulting in unsatisfied overall water splitting in alkaline media. Herein, we demonstrate the self-assembly of a new nanoforest electrocatalyst by ultrathin Ni(OH)2/Ni3S2 heterogeneous nanosheets (∼1.8 nm) using a high-temperature and large-potential electrodeposition technique. The surface atomic configuration of Ni3S2 is well-modulated by hetero-interface engineering with the Ni(OH)2 cocatalyst, effectively accelerating the Volmer step and OH− adsorption during the HER without sacrificing the oxygen evolution reaction (OER). The resultant electrocatalysts exhibit superior and stable electrocatalytic activity toward the HER and OER in 1 M KOH with small overpotentials of 50 mV and 210 mV at 10 mA cm-2, respectively. Using the Ni(OH)2/Ni3S2 nanoforest as dual-functional electrocatalysts, an alkaline electrolyzer can render 100 mA cm-2 at a very low cell voltage of 1.64 V while keep stable for 120 h at 1.55 V, which outperforms the best report for Ni-based electrocatalysts. This finding gives a new insight into the modulating surface atomic configuration for achieving highly active electrocatalysts for water splitting.