Bio-Inspired FeMo2S4 Microspheres as Bifunctional Electrocatalysts for Boosting Hydrogen Oxidation/Evolution Reactions in Alkaline Solution

Developing robust and effectual nonprecious electrocatalysts for the bifunctional hydrogen oxidation and evolution reactions (HOR and HER) in alkaline electrolyte is of critical significance for the realization of future hydrogen economy but challenging. Herein, this work demonstrates a new routine for the preparation of bio-inspired FeMo₂S₄ microspheres via the one-step sulfuration of Keplerate-type polyoxometalate {Mo₇₂Fe₃₀}. The bio-inspired FeMo₂S₄ microspheres feature potential-abundant structural defects and atomically precise iron doping and act as an effective bifunctional electrocatalyst for hydrogen oxidation/reduction reactions. The FeMo₂S₄ catalyst presents an impressive alkaline HOR activity compared to FeS₂ and MoS₂ with the high mass activity of 1.85 mA·mg^-1 and high specific activity as well as excellent tolerance to carbon monoxide poisoning. Meanwhile, FeMo₂S₄ electrocatalyst also displayed prominent alkaline HER activity with a low overpotential of 78 mV at a current density of 10 mA·cm^-2 and robust long-term durableness. Density functional theory (DFT) calculations indicate that the bio-inspired FeMo₂S₄ with a unique electron structure possesses the optimal hydrogen adsorption energy and enhanced adsorption of hydroxyl intermediates, which accelerates the potential-determining Volmer step, thus promoting the HOR and HER performance. This work provides a new pathway for designing efficient noble-metal-free electrocatalysts for the hydrogen economy.