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

Platinum (Pt) has been widely employed in photocatalytic H production. However, the influence of CO on proton reduction to H over Pt active species remains unknown. Herein, using Pt/NbO as a model catalyst, the role of Pt active species in CO-sensitive photocatalytic H evolution is evaluated. Our results reveal that Pt species exhibits superior activity in H production when the CO-to-Pt molar ratio is low (n/n ≤ 1.3), but their photocatalytic performance is suppressed at a high n/n ratio (>1000). By contrast, increasing the loading amount of Pt suppresses Pt species formation and the low valence state Pt species show inferior activity for H production, which is almost unaffected by the n/n 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 HO and Pt species and prevent the generation of *H species for H production. Significantly improving the H production rate by purging with argon suggests the importance of inhibiting the adsorption of CO on Pt 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 production.