Synergistic effect between platinum single atoms and oxygen vacancy in MoO₂ boosting pH-Universal hydrogen evolution reaction at large current density

Single-atomic or cluster-based precious metals provide an effective pathway to minimize the cost of catalysts. However, its stability at large current density is still a major hurdle to satisfy practical requirements for electrocatalytic Hydrogen evolution reaction (HER). Herein, we successfully anchored Pt single atoms (Pt SAs) in the oxygen vacancies (O_vac) of Molybdenum dioxide (MoO₂) as advanced HER electrocatalyst. Experimental and theoretical calculations results reveal that the O_vac can not only stabilize Pt SAs, but also modulate the electronic structure of the active site, enabling Pt SAs/MoO₂ to exhibit superior HER activity in a wide pH electrolyte at large current density. Especially, the 1.1 wt% Pt SAs/MoO₂ deliver ultralow overpotentials (9.3, 14, and 16 mV at 10 mA cm⁻²) and small Tafel slopes (28.78, 36.86, and 65.18 mV dec^-1) in acidic, alkaline, and neutral electrolytes, respectively. Moreover, it displays significantly enhanced mass activity of up to 28, 32, and 56 times compared to the benchmark 20 wt% Pt/C catalyst, and outstanding long-term durability (~200 h) at large current density of −1000 mA cm⁻². The significantly improved HER performances are mainly ascribed to the synergistic catalytic effects of between Pt SAs and O_vac in MoO₂. These impressive findings can provide insights into the rational design of electrocatalysts that used for future clean energy utilization.