Slow photons for solar fuels

Abstract Converting solar energy into hydrogen and hydrocarbon fuels through photocatalytic H 2 production and CO 2 photoreduction is a highly promising approach to address growing demand for clean and renewable energy resources. However, solar-to-fuel conversion efficiencies of current photocatalysts are not sufficient to meet commercial requirements. The narrow window of solar energy that can be used has been identified as a key reason behind such low photocatalytic reaction efficiencies. The use of photonic crystals, formed from multiple material components, has been demonstrated to be an effective way of improving light harvesting. Within these nanostructures, the slow-photon effect, a manifestation of light-propagation control, considerably enhances the interaction between light and the semiconductor components. This article reviews recent developments in the applications of photonic crystals to photocatalytic H 2 production and CO 2 reduction based on slow photons. These advances show great promise for improving light harvesting in solar-energy conversion technologies.