Single-atom catalysts offer a pathway to cost-efficient catalysis using the minimal amount of precious metals. However, preparing and keeping them stable during operation remains a challenge. Here we report the synthesis of double transition metal MXene nanosheets—Mo₂TiC₂T_x, with abundant exposed basal planes and Mo vacancies in the outer layers—by electrochemical exfoliation, enabled by the interaction between protons and the surface functional groups of Mo₂TiC₂T_x. The as-formed Mo vacancies are used to immobilize single Pt atoms, enhancing the MXene’s catalytic activity for the hydrogen evolution reaction. The developed catalyst exhibits a high catalytic ability with low overpotentials of 30 and 77 mV to achieve 10 and 100 mA cm⁻² and a mass activity about 40 times greater than the commercial platinum-on-carbon catalyst. The strong covalent interactions between positively charged Pt single atoms and the MXene contribute to the exceptional catalytic performance and stability.

单原子催化剂提供了使用最少数量的贵金属实现具有成本效益的催化的途径。然而，在操作期间准备并保持它们稳定仍然是一个挑战。在这里，我们报道了通过质子与Mo ₂的表面官能团之间的相互作用实现的电化学剥落，合成了双过渡金属MXene纳米片Mo ₂ TiC ₂ T _x，外层具有丰富的暴露基面和Mo空位。钛₂ T _x。形成的Mo空位用于固定单个Pt原子，从而增强MXene对氢释放反应的催化活性。所开发的催化剂表现出高的催化能力，具有低的30和77 mV的过电势，以实现10和100 mA cm ^-2的质量活性，并且其活性约为商业上的碳载铂催化剂的40倍。带正电的Pt单原子与MXene之间的强共价相互作用有助于实现出色的催化性能和稳定性。