2H-MoS₂ on Mo₂CT_<i>x</i> MXene Nanohybrid\nfor Efficient and Durable Electrocatalytic\nHydrogen Evolution

Abstract

The\ndevelopment of highly efficient and durable earth-abundant\nhydrogen evolution reaction (HER) catalysts is crucial for the extensive\nimplementation of the hydrogen economy. Members of the 2D MXenes family,\nparticularly Mo₂CT_<i>x</i>, have recently\nbeen identified as promising HER catalysts. However, their inherent\noxidative instability in air and aqueous electrolyte solutions is\nhindering their widespread use. Herein, we present a simple and scalable\nmethod to circumvent adventitious oxidation in Mo₂CT_<i>x</i> MXenes <i>via in situ</i> sulfidation\nto form a Mo₂CT_<i>x</i>/2H-MoS₂ nanohybrid. The intimate epitaxial coupling at the Mo₂CT_<i>x</i>/2H-MoS₂ nanohybrid\ninterface afforded superior HER activities, requiring only 119 or\n182 mV overpotential to yield −10 or −100 mA cm^–2_geom current densities, respectively. Density\nfunctional theory calculations reveal strongest interfacial adhesion\nwas found within the nanohybrid structure as compared to the physisorbed\nnanohybrid, and the possibility to tune the HER overpotential through\nmanipulating the extent of MXene sulfidation. Critically, the presence\nof 2H-MoS₂ suppresses further oxidation of the MXene layer,\nenabling the nanohybrid to sustain industrially relevant current densities\nof over −450 mA cm^–2_geom with\nexceptional durability. Less than 30 mV overpotential degradation\nwas observed after 10 continuous days of electrolysis at a fixed −10\nmA cm^–2_geom current density or 100,000\nsuccessive cyclic voltammetry cycles. The exceptional HER durability\nof the Mo₂CT_<i>x</i>/2H-MoS₂ nanohybrid presents a major step forward to realize practical implementation\nof MXenes as noble metal free catalysts for broad-based applications\nin water splitting and energy conversion.