Highly Sustainable h-BN Encapsulated MoS 2 Hydrogen Evolution Catalysts.

Despite the importance of the stability of the 2D catalysts in harsh electrolyte solutions, most studies have focused on improving the catalytic performance of molybdenum disulfide (MoS 2 ) catalysts rather than the sustainability of hydrogen evolution. In previous studies, the vulnerability of MoS 2 crystals is reported that the moisture and oxygen molecules can cause the oxidation of MoS 2 crystals, accelerating the degradation of crystal structure. Therefore, optimization of catalytic stability is crucial for approaching practical applications in 2D catalysts. Here, it is proposed that monolayered MoS 2 catalysts passivated with an atomically thin hexagonal boron nitride (h-BN) layer can effectively sustain hydrogen evolution reaction (HER) and demonstrate the ultra-high current density (500 mA cm⁻ 2 over 11 h) and super stable (64 h at 150 mA cm⁻ 2 ) catalytic performance. It is further confirmed with density functional theory (DFT) calculations that the atomically thin h-BN layer effectively prevents direct adsorption of water/acid molecules while allowing the protons to be adsorbed/penetrated. The selective penetration of protons and prevention of crystal structure degradation lead to maintained catalytic activity and maximized catalytic stability in the h-BN covered MoS 2 catalysts. These findings propose a promising opportunity for approaching the practical application of 2D MoS 2 catalysts having long-term stability at high-current operation.