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 (nCO/nPt ≤ 1.3), but their photocatalytic performance is suppressed at a high nCO/nPt ratio (> 1000). By contrast, increasing the loading amount of Pt suppresses Pt4+ species formation and the low valence state Pt species shows inferior activity for H2 production, which is almost unaffected by the nCO/nPt 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.