Highly Sustainable h‐BN Encapsulated MoS ₂ Hydrogen Evolution Catalysts

Abstract 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.