Controlling catalytic activity of gold cluster on MgO thin film for water splitting

Abstract

We propose that supported gold clusters on MgO thin film can potentially serve as an efficient photocatalyst for water splitting. The catalytic activity of the gold cluster is enhanced by excess electrons occupying its quantum well states (QWSs) and can be controlled by varying the oxide thickness, introducing defects/doping in the substrate, and modulating the plasmonic response of the Au cluster. We find that the bonding between the water molecule and certain QWSs can significantly reduce the water splitting energy barrier in its ground state. More importantly, the water splitting is nearly spontaneous when the QWS is photoexcited. First-principles real-time electron dynamics simulations reveal that the excited QWS in the supported gold cluster has a long lifetime on the scale of picoseconds. Generation of activated hydrogen atoms is predicted to occur spontaneously following photoexcitation, and the yield of H2 gas is maintained by enriching hydrogen concentration without poisoning the catalyst. These results illustrate promising routes for promoting photocatalysis via engineering the energy levels of supported metal clusters.