Identifying the Role of Pt Active Species in CO-Sensitive Photocatalytic H₂ Evolution

Platinum (Pt) has been widely employed in photocatalytic H₂ production. However, the influence of CO on proton reduction to H₂ over Pt active species remains unknown. Herein, using Pt/Nb₂O₅ as a model catalyst, the role of Pt active species in CO-sensitive photocatalytic H₂ evolution is evaluated. Our results reveal that Pt⁴⁺ species exhibits superior activity in H₂ production when the CO-to-Pt molar ratio is low (n_CO/n_Pt ≤ 1.3), but their photocatalytic performance is suppressed at a high n_CO/n_Pt ratio (>1000). By contrast, increasing the loading amount of Pt suppresses Pt⁴⁺ species formation and the low valence state Pt species show inferior activity for H₂ production, which is almost unaffected by the n_CO/n_Pt ratio. The CO-TPD results, in situ FTIR spectra, and DFT calculations indicate that the role of adsorbed CO molecules is to impede the interaction between H₂O and Pt⁴⁺ species and prevent the generation of *H species for H₂ production. Significantly improving the H₂ production rate by purging with argon suggests the importance of inhibiting the adsorption of CO on Pt⁴⁺ species. This study sheds light on the generation and transformation of active H species in CO-participated photocatalytic systems, which is missing in previous works, and is more significant for rationally designing Pt-based photocatalysts in large-scale H₂ production.