Reactive Deposition Versus Strong Electrostatic Adsorption (SEA): A Key to Highly Active Single Atom Co‐Catalysts in Photocatalytic H2 Generation

Abstract In recent years, the use of single atoms (SAs) has become of a rapidly increasing significance in photocatalytic H 2 generation; here SA noble metals (mainly Pt SAs) can act as highly effective co‐catalysts. The classic strategy to decorate oxide semiconductor surfaces with maximally dispersed SAs relies on “strong electrostatic adsorption” (SEA) of suitable noble metal complexes. In the case of TiO 2 – the classic benchmark photocatalyst – SEA calls for adsorption of cationic Pt complexes such as [(NH 3 ) 4 Pt] 2+ which then are thermally reacted to surface‐bound SAs. While SEA is widely used in literature, in the present work it is shown by a direct comparison that reactive attachment based on the reductive anchoring of SAs, e.g., from hexachloroplatinic(IV) acid (H 2 PtCl 6 ) leads directly to SAs in a configuration with a significantly higher specific activity than SAs deposited with SEA – and this at a significantly lower Pt loading and without any thermal post‐deposition treatments. Overall, the work demonstrates that the reactive deposition strategy is superior to the classic SEA concept as it provides a direct electronically well‐connected SA‐anchoring and thus leads to highly active single‐atom sites in photocatalysis.