First-principles thermodynamic screening approach to photo-catalytic water splitting with co-catalysts

TL;DR

This paper presents a first-principles computational approach to identify effective catalyst and co-catalyst combinations for photo-catalytic water splitting, emphasizing the role of co-catalysts like gold clusters.

Contribution

It introduces a novel screening protocol that explicitly accounts for photo-generated charges and uses the hole energy as a key descriptor, revealing new insights into water oxidation on TiO2.

Findings

Small Au clusters outperform extended Au surfaces for water oxidation.

Water oxidation on TiO2 is more complex than previously understood.

Most studied Au clusters are better suited for photo-oxidation than bulk gold.

Abstract

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.