The search for efficient electrocatalysts as counter electrode materials for dye-sensitized solar cells: mechanistic study, material screening and experimental validation

In recent years, there has been a significant increase in the studies on effective energy-conversion devices, including photovoltaics and fuel cells, which aim to alleviate the enormous energy demand, as well as the environmental pollution issues associated with current power consumption. Among these devices, dye-sensitized solar cells (DSCs) have received significant attention owing to their simple fabrication procedure, cost-effectiveness and high-power-conversion efficiency. The counter electrode (CE) of the DSCs is an important component and generally uses platinum as its benchmark material, the high cost and scarcity of which have limited the broad application of the DSCs. Thus, substantial effort has been devoted to seek active CE materials with low cost, high electrocatalytic activity and excellent stability. Nevertheless, this is generally achieved via a 'trial-and-error' method owing to the lack of information on the mechanism of the electrocatalytic reaction on the CE's surface. This report summarizes the recent advances in the mechanistic study of the interfacial electrocatalytic reaction on CE materials, as well as the establishment of a rational screening protocol for efficient CE materials. Furthermore, several outstanding CE materials developed via this protocol have been reviewed. The demonstrated combined approach can be extended to the studies of other essential electrocatalytic reactions.