Polymeric watersplitting photocatalysts; a computational perspective on the water oxidation conundrum

A computational scheme to predict the thermodynamic ability of photocatalysts to drive both of the watersplitting half reactions, proton reduction and water oxidation, is discussed, and applied to a number of polymeric systems to explain their apparent inability to oxidise water. We predict that the poly(p-phenylene) (PPP) is thermodynamically unable to oxidise water and that PPP is hence unlikely to split water in the absence of an external electrical bias. For other polymers, however, for example carbon nitride, the lack of oxygen evolution activity appears kinetic in origin and hence a suitable co-catalyst could potentially transform them into true watersplitting photocatalysts.