Unlike catalytic reactions thermally driven by metal nanoparticles, reaction rates in photocatalysis do not scale with either the density of nanoparticles or their size. Because of the complexity of multicomponent photocatalysts in powder form, this lack of correlation, routinely observed for decades, is still not understood. In order to explore this phenomenon, H2 production from ethanol over Au clusters with different coverages deposited on single-crystal rutile TiO2(110) were studied by scanning tunneling microscopy and online mass spectrometry. There is a nonlinear increase of the H2 production with increasing gold coverage. The key determining factor appears to be the Au intercluster distance. Increasing this distance resulted in an increase in the normalized production. These results are explained in terms of competition between clusters for excited electrons to reduce H+ (of surface OH groups) to H2. It was possible to determine the proportionality factor between the hydrogen production and the number of absorbed photons. A slope close to 1 is found, which is in line with the
|Original language||English (US)|
|Number of pages||12|
|State||Published - Jul 29 2019|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This work was supported by SABIC, the European Research Council through Advanced Grant ENERGYSURF (GT), EU COST Action CM1104, and the Royal Society (UK) through a Wolfson Research Merit Award to G.T.