Solar energy conversion and storage is one of the most pressing research topics in the physical and chemical sciences, and its prospects for success have implications for the entire planet. Challenges such as a rapidly growing global population, the concomitant growth in greenhouse gas emissions, and the impact that growth has on climate change make finding low-carbon solutions to energy production and storage all the more critical. The sun provides far more clean energy than humans can actually utilize, but due to the fundamental problem of fluctuating availability of sunlight, solar energy has to be converted into storable forms of energy before it can be applied more broadly to meet a larger fraction of global energy needs.

This special section of the Journal of Photonics for Energy on solar fuels photocatalysis centers broadly on ways to convert solar energy to usable fuel—either by reducing ${\mathrm{CO}}_2$ to carbon-based fuels, or by reducing protons to hydrogen.

More specifically, the special section covers several important long-standing and emerging areas in solar fuels photocatalysis. Shelton et al. describe some of the latest advances in the understanding of photocatalytic water oxidation with iron oxide nanoparticles under visible light; Liu et al. describe the role of highly dispersed Cu sites on ${\mathrm{TiO}}_2$ in the photocatalytic reduction of ${\mathrm{CO}}_2$; Takashima et al. dive still more deeply into the electrocatalytic ${\mathrm{CO}}_2$ reduction mechanism at Cu, elucidating the role of proton-donating compounds in proton-coupled electron-transfer (PCET)-mediated reduction of ${\mathrm{CO}}_2$ at Cu electrodes; Janczarek et al. present detailed work on the interplay of ${\mathrm{TiO}}_2$ crystal facets and surface plasmon resonance-driven photocatalytic ${\mathrm{H}}_2$ generation at composites comprising ${\mathrm{TiO}}_2$, Cu, and Ag, providing important materials-specific and mechanistic insights into a widely studied but still inadequately understood research area.

Also included are some timely reviews, including an up-to-date minireview of photoelectrochemical water splitting by Peerakiatkhajohn et al., and reviews on emerging topics, including the incorporation of spinel ferrites into solar fuels photocatalysis by Taffa et al., and that of exploitation of photonic crystals for solar fuels photocatalysis by Pietron and DeSario.

The articles in this special section provide a good overview of recent progress in solar fuels photocatalysis, giving insight into the ever-increasing variety of materials and techniques—already existing and emerging—in this exciting research field.