SacrificialAgent-Controlled Photodeposition: RevealingPt-Photodeposition Key Features of Pt-Nanoparticle Co-catalysts forMaximized Photocatalytic H₂ Evolution

Photocatalytic H₂ production from TiO₂ substrates (and many other common semiconductors) relies on the use of a suitable co-catalyst. The most widely used co-catalyst is Pt that is typically photodeposited as metallic Pt⁰ nanoparticles (NPs) on various titania structures. In this Pt photodeposition process, parameters such as the Pt concentration in the solution or the nature of the sacrificial agents strongly affect the NP deposition amount, the particle size, and its distribution. Despite considerable investigations, unifying concepts that connect Pt-deposit features with H₂ evolution efficiency focus mainly on a critical Pt loading amount but are often inconclusive. In the present work, we use thin-film sputter-deposited anatase layers as well-defined photoabsorbers for Pt deposition under a wide range of conditions, characterize the NPs, and measure photocatalytic H₂ evolution. From the results, we find that a unifying criterion for achieving a maximized co-catalytic efficiency of Pt deposits is to overcome a critical Pt particle density, independent of the detailed particle features of Pt deposition conditions.