We adapt the computational hydrogen electrode approach to explicitly account
for photo-generated charges and use it to computationally screen for viable
catalyst/co-catalyst combinations for photo-catalytic water splitting. The hole
energy necessary to thermodynamically drive the reaction is employed as
descriptor for the screening process. Using this protocol and hybrid-level
density-functional theory we show that water oxidation on bare TiO2 surfaces is
thermodynamically more complex than previously thought. This motivates a
screening for suitable co-catalysts for this half-reaction, which we carry out
for Au particles down to the non-scalable size regime. We find that almost all
small Au clusters studied are better suited for water photo-oxidation than an
extended Au(111) surface or bare TiO2 facets.Comment: 5 pages, 3 figure
