Construction of flower-like nanoassembly P-doped MOF-derived MoS2/Co9S8 grown on hexagonal microporous alumino-silicate framework for overall water splitting in alkaline media

Abstract

Water splitting is a noteworthy process in the field of hydrogen and oxygen gas production. MoS2 has emerged as an effective material for catalyzing water splitting; however, its low electronic conductivity and oxidative corrosion in environmental conditions suppress its practical applications in electrolyzers. Herein, we constructed a new hetero-nanostructure composed of MoS2 and Co9S8 phases, which is assembled onto the hexagonal microporous alumino-silicate (HMS) structure. Different combinations ratios of Mo and Co elements in hetero-nanostructures offered tremendous opportunities for morphology control and, further, modification of chemical and physical properties to enhance the overall water splitting process. HMS/MoS2/Co9S8-31 (with the mole ratio of 3:1 for Mo:Co) showed synergistically enhanced electrocatalytic performance for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with overpotentials of −127 and 280 mV at 10 mA cm−2, respectively. In the next step, phosphorization of HMS/MoS2/Co9S8-31 was performed via a simple one-step route (HMS/MoS2/Co9S8/P-31), so the overpotentials were reduced to −85 and 200 mV, which shows dramatic improvement in the overall water splitting performance of electrocatalyst. In addition, for a symmetrical electrolyzer, a current density of 10 mA cm−2 was obtained at a quite low cell voltage of 1.56 V. Systematic studies on HMS/MoS2/Co9S8/P-31 and a set of finely designed control catalysts suggest that the enhanced electrocatalytic behavior should be related to electronic coupling effect and modulation between MoS2 and Co9S8 and the advantage of the ordered HMS architecture. In addition, phosphorus doping can modify the electronic properties of hetero-nanostructure and facilitates electron transfer between MoS2 and Co9S8 hetero-phases.