Research

Photocatalytic water splitting reactions  occur in two parts: water oxidation to oxygen and protons and proton reduction to evolve hydrogen. Unfortunately, these two half-reactions require different conditions. Oxidation proceeds best under more basic conditions where hydroxyl anions are more common, whereas the reductive step needs acidic conditions with a higher proton concentration. As these self-evidently cannot occur simultaneously in the same place, this project proposes to attempt two methods for performing the two half-reactions in the same reaction vessel but with either spatial or temporal separation. Taking inspiration from energy ratchet mechanisms used by molecular machines, we will switch between acidic and basic conditions using a photo-switchable acid. The photo acid will act as a stimuli responsive carrier for protons released by the oxidation of water which can either shuttle them to the reductive site, or store them until the conditions are switched to favour reduction. This way, we will be able to independently optimise the two halves of the reaction, overcoming the inherent limitations of the chemistry under continuous conditions.