Full-spectrum utilization of solar energy for simultaneous CO2 reduction and seawater desalination

Abstract

Photocatalytic CO₂ reduction, as a highly integrated solar fuel generation technology, cannot efficiently utilize infrared light, resulting in a severe waste of solar energy. Given the fact that bifunctional polyaniline can conduct photocatalysis and promote water evaporation at the same time, integrating the advantages of a gas diffusion layer in mass transfer, we proposed a novel layout of the reacting system. In this constructed three-phase interface, polyaniline exhibited high activity for CO₂ reduction, rather than hydrogen evolution. Through quasi-in situ Raman spectroscopy, we found that the introduced copper–cobalt composite oxides would be reduced to cuprous oxide/tricobalt tetroxide once photocatalysis starts. The highest achieved selectivity of ethanol-based C₂₊ products was >90%. The presence of a greater number of asymmetric adsorption sites between copper and cobalt facilitated C–C coupling, further proved by the density functional theory analysis. For water evaporation, the achieved energy conversion efficiency of solar to vapor was 71.0%. The evaporation was activated via the unabsorbed light by the photocatalyst and the unused light that had been absorbed. The vapor flux was driven across the hydrophobic gas diffusion layer into the flow in the backplate by the temperature gradient between each side of the gas diffusion layer. Subsequently, desalted water was obtained by condensation.