Enhanced photoelectrochemical water splitting using oxidized mass-selected Ti nanoclusters on metal oxide photoelectrodes

We report an enhancement of up to 85% in the photocurrent generated from a bismuth vanadate photoanode through the prior deposition of mass-selected Ti nanoclusters onto the semiconductor surface. We studied the effect of a variety of cluster sizes, deposited at the same density and with the same energy (1.5 keV per cluster), over the surface of separate BiVO4 photoanodes in a cluster beam source. Using mass-selected clusters of a narrow size distribution, we were able to reveal that the photocurrent is strongly dependent on the cluster size (in the size regime examined), leading to an increase of up to 85% in the photocurrent for Ti2000±54 clusters. Remarkably the quantities of metal used to achieve such an enhancement are on the 2.8 × 10−7 g cm−2 level, resulting from the optimum density which is approximately 0.4 monolayers. This work highlights the importance of submonolayer surface treatments, using accurate mass-selected nanoclusters, for the modification of semiconductor surfaces in order to improve the interfacial charge transfer properties.