Integrable utilization of intermittent sunlight and residual heat for on-demand CO2 conversion with water

Abundant residual heat from industrial emissions may provide energy resource for CO2 conversion, which relies on H2 gas and cannot be accomplished at low temperatures. Here, we report an approach to store electrons and hydrogen atoms in catalysts using sunlight and water, which can be released for CO2 reduction in dark at relatively low temperatures (150−300 °C), enabling on-demand CO2 conversion. As a proof of concept, a model catalyst is developed by loading single Cu sites on hexagonal tungsten trioxide (Cu/WO3). Under light illumination, hydrogen atoms are generated through photocatalytic water splitting and stored together with electrons in Cu/WO3, forming a metastable intermediate (Cu/HxWO3). Subsequent activation of Cu/HxWO3 through low-temperature heating releases the stored electrons and hydrogen atoms, reducing CO2 into valuable products. Furthermore, we demonstrate the practical feasibility of utilizing natural sunlight to drive the process, opening an avenue for harnessing intermittent solar energy for CO2 utilization. Residual industrial heat could be harnessed as an energy source for CO2 conversion. Here the authors present a method for storing electrons and hydrogen in catalysts using light and water, which are then released upon heating to enable CO2 reduction with intermittent sunlight and residual heat.