Pt Single Atoms on TiO2 Polymorphs—Minimum Loading with a Maximized Photocatalytic Efficiency

Abstract For more than 20 years, Pt/TiO 2 represents the benchmark photocatalyst/co‐catalyst platform for photocatalytic hydrogen (H 2 ) generation. Here, single atom (SA) Pt is decorated on different polymorphs of TiO 2 (anatase, rutile, and the mixed phase of P25) using a simple immersion anchoring approach. On P25 and anatase, Pt SAs act as highly effective co‐catalyst for pure water splitting with a photocatalytic H 2 evolution activity (4600 µ mol h −1 g −1 )—on both polymorphs, SA deposition yields a significantly more active photocatalyst than those decorated with classic Pt nanoparticles or conventional SA deposition approaches. On rutile, Pt SAs provide hardly any co‐catalytic effect. Most remarkable, for P25, the loading of Pt SAs from precursor solution with a very low concentration ( < 1 ppm Pt) leads already to a maximized co‐catalytic effect. This optimized efficiency is obtained at 5.3 × 10 5 atoms µ m −2 (at macroscopic loading of 0.06 at%)—for a higher concentration of Pt (a higher density of SAs), the co‐catalytic efficiency is significantly reduced due to H 2 /O 2 recombination. The interactions of the SA Pt with the different polymorphs that lead to this high co‐catalytic activity of SA Pt at such low concentrations are further discussed.