Bifunctional catalysts of Ni nanoparticle coupled MoO₂ nanorods for overall water splitting

The development of active and cost-effective bifunctional catalysts is crucial for water dissociation through electrolysis. In this study, bifunctional catalysts with Ni nanoparticles (NPs) anchored on MoO₂ nanorods have been synthesized via in situ dissolution of NiMoO₄-ZIF under an inert atmosphere without using hydrogen gas. The Ni-MoO₂ catalyst exhibits high electrocatalytic activity by modulating the calcination temperature. Benefitingfrom the MOF transformation and accompanying Ni particles' outward diffusion, a precisely designed interface heterostructure between Ni and MoO₂ was constructed. As a result, the optimized Ni-MoO₂ catalyst achieves extremely low overpotentials of only 24 mV and 275 mV at 10 mA cm^-2 for the hydrogen evolution reaction and oxygen evolution reaction, respectively. Furthermore, the catalyst required a small cell voltage of 1.55 V to deliver a current density of 10 mA cm^-2 and remained stable over 20 h for overall water splitting. The proposed MOF-derived heterojunction protocol provides a general approach for designing and fabricating transition metal oxide catalysts for water electrolysis.