Delaminated MBene sheets beyond usual 2D transition metal materials for securing Pt single atoms to boost hydrogen evolution

The use of a minimum amount of active metal makes single-atom catalysts (SACs) an effective route to economically catalyze electrochemical reactions. However, maintaining their desired stability during synthetic and catalytic processes under harsh conditions is still a challenge and is critically influenced by the appropriate support to ensure strong isolated SACs-host interactions. Herein, we report a selective etching-expanding preparation of layered ternary transition metal boride nanosheets - MoAl_1−xB with a rich exposition of basal planes and Mo-vacancy defect sites for immobilizing Pt single atoms (SAs) via adsorption and doping behaviors. The Pt-MoAl_1−xB material impressively enhances hydrogen evolution reaction activities with low overpotential (η) values of 32 and 18 mV to achieve 10 mA cm⁻² in alkaline and acid media, respectively. Particularly, it achieves superior mass activity, specific activity, and turnover frequency as compared to Pt-Mo₂C, Pt-MoS₂, and commercial Pt-C catalysts. An electrolyzer cell based on a Pt-MoAl_1−xB cathode can well deliver industrial-level current density with good efficiency and durability. Experiment and theoretical analyses indicate that MoAl_1−xB can form strong interactions with Pt SAs and result in enriched charge density and d-electrons of individual Pt atoms, leading to exceptional catalytic HER performance and stability. Thus, it has potential as a high-efficiency HER catalyst for practical water electrolysis.