Ultrahigh Mass Activity for the Hydrogen Evolution Reaction by Anchoring Platinum Single Atoms on Active {100} Facets of TiC via Cation Defect Engineering

Abstract Improving the platinum (Pt) mass activity for low‐cost electrochemical hydrogen evolution is an important and arduous task. Here, a selective etching‐reducing fluidized bed reactor technique is reported to create Ti vacancies and firmly anchor single Pt atoms on the active {100} facets of titanium carbide (TiC) to increase the Pt utilization efficiency and improve catalytic activity significantly by a synergistic effect between Ti vacancies and Pt atoms. The generated Ti vacancies are negatively charged and stabilize Pt atoms by forming covalent PtC bonds, showing excellent long‐term durability. Pt single atoms (ultralow load of 1.2 µg cm⁻²) on the defective TiC {100} show remarkable activity (24.9 mV at 10 mA cm⁻²) and a mass activity (49.69 A mg⁻¹) ≈190 times that of the state‐of‐the‐art PtC catalyst and nearly double the previously reported best values. The developed cation defect engineering exhibits excellent potential for fabricating next‐generation advanced single‐atom catalysts for large‐scale hydrogen evolution at a low cost.