Chapter 8: Degradation of Semiconductor Electrodes in Photoelectrochemical Devices: Principles and Case Studies

The performance, durability, and reliability of photoelectrochemical (PEC) devices rely on the stability and efficiency of single components. Although some metal oxide semiconductors have been considered as thermodynamically stable under operating conditions, most of them suffer from (photo)chemical degradation. To overcome present stability limitations, a comprehensive understanding of degradation mechanisms and a careful study of the impact of degradation on the performance are required. First, we discuss thermodynamic and kinetic aspects of degradation to predict material stability, focusing on the light absorber–electrolyte interface. Second, we present different degradation mechanisms and methodologies for analyzing failure pathways of p- and n-type metal oxide semiconductors. Detailed study of chemical and photochemical instability is revealed by investigating morphology and chemical composition changes and their relationship to materials’ performance through the use of a multimodal characterization approach. This understanding may enable the development of tailored protective coatings, as well as the discovery of next generation, highly durable and efficient PEC materials.