Semiconducting quantum dots for artificial photosynthesis

Sunlight is our most abundant, clean and inexhaustible energy source. However, its diffuse and intermittent nature makes it difficult to use directly, suggesting that we should instead store this energy. One of the most attractive avenues for this involves using solar energy to split H2O and afford H2 through artificial photosynthesis, the practical realization of which requires low-cost, robust photocatalysts. Colloidal quantum dots (QDs) of IIB–VIA semiconductors appear to be an ideal material from which to construct highly efficient photocatalysts for H2 photogeneration. In this Review, we highlight recent developments in QD-based artificial photosynthetic systems for H2 evolution using sacrificial reagents. These case studies allow us to introduce strategies — including size optimization, structural modification and surface design — to increase the H2 evolution activities of QD-based artificial photosystems. Finally, we describe photocatalytic biomass reforming and unassisted photoelectrochemical H2O splitting — two new pathways that could make QD-based solar-to-fuel conversion practically viable and cost-effective in the near future. Semiconducting quantum dots (QDs) can serve as light-absorbing components in efficient artificial photosynthetic systems for H2 evolution. This Review describes how we can optimize QDs for H2 evolution using sacrificial reductants, before moving on to sustainable strategies for the photolysis of biomass or H2O.