Interface engineering of Mo-doped Ni₉S₈/Ni₃S₂ multiphase heterostructure nanoflowers by one step synthesis for efficient overall water splitting

Accelerating charge transfer efficiency by constructing heterogeneous interfaces on metal-based substrates is an effective way to improve the electrocatalytic performance of materials. However, minimizing the substrate-catalyst interfacial resistance to maximize catalytic activity remains a challenge. This study reports a simple interface engineering strategy for constructing Mo-Ni₉S₈/Ni₃S₂ heterostructured nanoflowers. Experimental and theoretical investigations reveal that the primary role assumed by Ni₃S₂ in Mo-Ni₉S₈/Ni₃S₂ heterostructure is to replace nickel foam (NF) substrate for electron conduction, and Ni₃S₂ has a lower potential energy barrier (0.76 to 1.11 eV) than NF (1.87 eV), resulting in a more effortless electron transfer. The interface between Ni₃S₂ and Mo-Ni₉S₈ effectively regulates electron redistribution, and when the electrons from Ni₃S₂ are transferred to Mo-Ni₉S₈, the potential energy barriers at the heterogeneous interface are 1.06 eV, lower than that between NF and Ni₃S₂ (1.53 eV). Mo-Ni₉S₈/Ni₃S₂-0.1 exhibited excellent oxygen evolution reaction (OER)/hydrogen evolution reaction (HER) bifunctional catalytic activity in 1 M KOH, with overpotentials of only 223 mV@100 mA cm^-2 for OER and 116 mV@10 mA cm^-2 for HER. Moreover, when combined with an alkaline electrolytic cell, it required only an ultra-low cell voltage of 1.51 V to drive a current density of 10 mA cm^-2. This work provides new inspirations for rationally designing interface engineering for advanced catalytic materials.