Minuscule Amounts of Pt Single Atoms Selectively Loaded on Minor (101) Facet of Anatase Crystallites Enables Outstanding Utilization Efficiency for Photocatalytic H2 Production

Pt single atoms (SAs) on TiO₂ have been identified as effective co-catalysts in solar photocatalytic H₂ production. In this study, Pt SAs is deposited on single crystal anatase nanosheets (NSs) with minor (101) and major (001) facets and expose them to various thermal treatments in air, Ar, and Ar-H₂ environments. It is found that through Ar-H₂ annealing Pt-species can be accumulated exclusively on the minor (101) facets, i.e., they can be concentrated selectively on the facet where electron exit occurs. This optimally establishes a high photocatalytic H₂ evolution efficiency for an extremely low overall Pt SA loading of ≈0.005 wt.% on the anatase crystallites. For this most active SA placement, 11.7 mmol g⁻¹ h⁻¹ H₂ production is obtained with a turnover frequency (TOF) up to 253 #H₂ site⁻¹ s⁻¹. Note that the corresponding Pt SAs density of 3.1 × 10⁴ atoms µm⁻² is established by loading from only 0.2 µm Pt solution. These findings demonstrate that placing a very low density of Pt SAs as an electron transfer co-catalyst onto the electron exit sites of a light-harvesting structure (i.e., there where it is needed) can provide a most active photocatalytic structure with an outstanding Pt utilization.