Understanding the Photoelectrochemical Behavior of Metal Nanoclusters: A Perspective

Since the invention of metal nanocluster (NC)-based photoelectrochemical (PEC) devices, limited progress has been made in this area due to various intricacies associated with this new class of photoactive nanomaterials. Recent research has shown that NC–TiO2 photoelectrodes possess charge separation and transfer complexities that are not seen in dye–TiO2 or quantum dot–TiO2 photoelectrodes. Even the degradation mechanism of NC-based photoelectrodes has a multitude of complexities, such that the degradation of NCs can have a silver lining of introducing plasmons to enhance charge separation in NC–TiO2 photoelectrodes. Therefore, NC-based photoelectrodes require a comprehensive overview from a photoelectrochemistry perspective to better understand these systems. In this Perspective, we provide a review of recent progress in understanding the degradation and charge transfer mechanisms of NC–TiO2 photoelectrodes. We also provide an overview of the various methodologies to control the properties of NCs for PEC applications and how these variables have been utilized to improve NC-based PEC device performance. Finally, we discuss the future of NC-based PEC devices and highlight the immense research opportunities present in this field.