(Invited) Synergistic Effects between Surface Charge and Catalytic Site in Photoelectrochemical Water Splitting Reactions

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Photoelectrochemical water splitting promising a practical route toward solar energy harvesting. The successful completion of this reaction requires coordination between light absorber and catalysis. It is often presumed that catalysis is a limiting factor in this chain of events, whereas little attention has been paid to the synergistic effect between the charge concentration and catalytic site density. In this talk, we will examine the interplays between these two key factors. We will start with a discussion on recent literature reports that point to the importance of coordination between these two factors and then discuss how these two variables can be controlled separately. We will move on to present detailed studies on water oxidation model reactions, which represent a bottleneck in the solar fuel synthesis efforts. We show that at high surface charge concentrations, each catalytic site acts independently, whereas there are clear cooperative behaviors among catalytic sites at low surface charge concentrations. It is implied that having an overload of co-catalysts is not always desired. The results are expected to serve as a guideline for future efforts aimed at optimizing photocatalyst designs.