Energy-efficient ultrafast microwave crystalline phase evolution for designing highly efficient oxygen evolution catalysts

Abstract

Lowering the production cost while maintaining the superb activity of catalysts for sluggish oxygen evolution reaction (OER) is the utmost challenge towards the success of electrolytic hydrogen-based green economy. Here, we report a fast (seconds scale) and very low energy-consuming recrystallization strategy for the universal development of nickel-iron-based sulfide, selenide and phosphide nanostructures with the state-or-the-art OER activity. Amorphous irregular bulk morphology of the iron nitrate treated nickel foam rapidly recrystallizes into the uniform nanostructures of sulfide, selenide and phosphide phases by microwave ultrafast thermal treatment upon graphene substrate. As-developed nanosheets of iron-doped Ni3S2/NiS in-plane heterostructure shows exceptionally high OER activity, with an overpotential of only 187 mV at 10 mA cm-2. It also requires only 289 mV to achieve a very high current density of 500 mA cm-2, which is well below the well-recognized target value (<300 mV) for commercial use. Comprehensive analysis reveals that NiS phase of Ni3S2/NiS selectively transforms into an amorphous (oxy)hydroxide phase under OER condition along with the in-situ yield of iron-doped Ni3S2/NiOOH heterostructure with a high activity. This efficient recrystallization protocol into high performance catalytic nanostructures is not only interesting for generating diverse crystalline phases, but also highly important for the low-cost practical utilization.