Similar Looks, Different Photoelectrochemical Behavior: Unique Aspects of Metal-Nanocluster-Sensitized Electrodes

Metal nanoclusters (NCs) were initially used in light-harvesting applications as mere alternatives to traditional photosensitizers; therefore, NCs are often evaluated using a similar set of parameters as those developed for their traditional counterparts. Despite the resemblance in the design architectures and working principles of NC-based and traditional-sensitized photoelectrodes, recent studies have revealed that the photoelectrochemical (PEC) attributes of NC-sensitized photoelectrodes are distinctly different. Therefore, it is important to redefine the criteria used for assessing NCs in energy conversion devices. In this Focus Review, we present a comprehensive overview of some unique PEC behavior of NC-sensitized photoelectrodes. We also provide a mechanistic description of the photodegradation route and how it can be manipulated to compensate for photosensitization loss in NCs under practical operating conditions. Finally, we discuss future research directions to achieve a better understanding of the unique PEC behavior that will help to establish new design principles.