Identifying the Role of Pt Active Species in CO‐Sensitive Photocatalytic H 2 Evolution

Abstract Platinum (Pt) has been widely employed in photocatalytic H 2 production. However, the influence of CO on proton reduction to H 2 over Pt active species remains unknown. Herein, using Pt/Nb 2 O 5 as a model catalyst, the role of Pt active species in CO‐sensitive photocatalytic H 2 evolution is evaluated. Our results reveal that Pt 4+ species exhibits superior activity in H 2 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 Pt 4+ species formation and the low valence state Pt species show inferior activity for H 2 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 H 2 O and Pt 4+ species and prevent the generation of *H species for H 2 production. Significantly improving the H 2 production rate by purging with argon suggests the importance of inhibiting the adsorption of CO on Pt 4+ 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 H 2 production.