Photoelectrochemical Water Splitting: Challenges and Perspectives
Prof. Laurie Peter, University of Bath/UK
Using sunlight to split water into oxygen and hydrogen offers a sustainable energy future based on a hydrogen economy. Interest in the process of photoelectrolysis at semiconductor electrodes was sparked by the much cited 1974 Nature paper by Fujishima and Honda who demonstrated that water could be split using a titanium dioxide electrode illuminated with ultraviolet light. In spite of over 30 years of research, realization of a stable, efficient low cost system for water splitting that utilizes the visible solar spectrum remains elusive. A promising device is the tandem photoelectrolysis cell which combines a water splitting cell in optical series with a solar cell that provides additional voltage to help drive the reaction. The thermodynamic constraints on efficiency are well understood, but the importance of kinetics in determining practical performance is only now becoming clear. Some of the new experimental methods that are being used to study the kinetics of the light-driven reactions involved in photoelectrolysis will be discussed and illustrated by their application to the characterization of α-Fe2O3 (hematite) electrodes, which have been proposed as a component of tandem photoelectrolysis cells.