Unraveling oxygen vacancy-driven catalytic hydrogen evolution activity and stability over atomic layer-deposited platinum cluster catalysts

Utilizing metal–oxygen vacancy (Ov) synergy to modulate catalytic performance is an efficient route in heterogeneous catalysis. However, the quantitative tuning of the Ov concentration and the corresponding establishment of Ov concentration–performance relationship have been rarely reported. Herein reducible MoO₃ nanorod-supported Pt catalysts with high-dispersion clusters and specific Ov concentrations were finely constructed by combining atomic layer deposition and the designed hydrogen activation strategy. The Pt clusters (Pt_n) deposited on MoO₃ can promote Ov generation through the hydrogen spillover effect, which also serve as the anchoring sites for Pt clusters, inhibiting their agglomeration. The independent modulation of Ov concentration of MoO_3−x was achieved while preserving a nearly unchanged Pt particle size, and a clear volcano-shape relationship between Ov concentration and catalytic activity was established. The optimized Pt_n/MoO_3−x-150R cluster catalysts with a mean particle size of 1.41 nm and a suitable Ov concentration (5.58 × 10¹³ spin per g) exhibit optimized H₂ evolution activity and durability for the hydrolytic dehydrogenation reaction of ammonia borane (AB), whose activity is 5.7-fold higher than that of the as-prepared Pt_n/MoO₃ catalysts. Multiple characterization studies and theoretical calculation results indicate that the electron-rich Pt cluster is responsible for the activation of AB and Ov affords the adsorption site for the H₂O molecule, and the synergy of Pt_n–Ov dual sites facilitates the adsorption–dissociation of H₂O molecules, which is the rate-determining step. This study will provide deep insights for the rational design of dual-site catalysts by utilizing the synergy between metal clusters and oxygen vacancies with suitable concentration.