Concepts of Photoelectrochemical Energy Conversion and Fuel Generation

This chapter provides an introduction to many of the key concepts that underlie electrochemical, photoelectrochemical, and photovoltaic energy conversion. The aim is to provide a scientific basis for understanding the in-depth chapters that follow in this book. Following a presentation of fundamental aspects of solid–solid and solid–liquid semiconductor junctions in the dark, an overview of the various ways that such junctions are utilized and arranged in integrated solar fuels generators is provided. Key differences between electrochemical processes at metal and semiconductor electrodes, the role of defects in charge transfer across semiconductor–electrolyte interfaces, and the basic processes leading to photovoltage and photocurrent generation of illuminated interfaces are presented. The ongoing challenge of creating integrated solar fuel generators that are simultaneously efficient, stable, and scalable is discussed and the search for new materials that can address outstanding property gaps is highlighted.