Facile and one-step synthesis of a free-standing 3D MoS2–rGO/Mo binder-free electrode for efficient hydrogen evolution reaction

Abstract

A free-standing 3D MoS₂/Mo electrode was prepared via a facile, one-step hydrothermal method wherein the Mo foil itself acted as the Mo source and thio-urea as the S source. When directly used as a hydrogen evolution reaction (HER) electrode, the as-prepared MoS₂/Mo exhibited a low onset potential of 120 mV, requiring an overpotential of only 334 mV to reach a current density of 100 mA cm⁻² while maintaining its catalytic activity for over 20 h. The activation energy of the reaction was determined to be ∼120 meV by temperature-dependent HER studies. In addition, we have also shown that MoS₂ structures can be repetitively grown on Mo foil for subsequent HER application by etching MoS₂ with H₂O₂. The HER performance was enhanced further by incorporating reduced graphene oxide (rGO) into the 3D MoS₂/Mo electrode, which facilitated better electron transfer through rGO. The onset potential of the MoS₂–rGO/Mo was 100 mV (which is 20 mV lower than that of the MoS₂/Mo electrode) and it required 291 mV to achieve a current density of 100 mA cm⁻². The catalysts were also found to be highly durable.