Post-Illumination Photoconductivity Enables Extension of Photo-Catalysis after Sunset

Cloud-cover-induced frequent and sharp dips in sunlight as well as diminished solar flux during the evenings of peak energy demand are major challenges in solar energy harvesting. Persistent and memory-based photocatalysts that efficiently operate under low light fluxes beyond sunset, are a potential solution to address and mitigate these challenges. This review describes examples of persistent photocatalysis systems based on charge injection into multivalent charge storage materials that allow post-illumination discharging and charge carrier generation that increase or maintain the catalysis rate. Persistent photocatalysis in defect-laden charge storage materials with multivalent states combined with slow charge release associated with electronic persistent photoconductivity results in giant persistent photocatalysis that can last more than an hour after the illumination is shut off. Strategies are suggested to develop persistent photocatalysis by improved charge separation and present figures of merit for evaluating persistent photocatalysis efficiency and performance. Furthermore, this could enable the use of such material systems in environmental applications such as photocatalytic coatings for the remediation of air pollution that continue to function into the night and self-cleaning applications that continue to disinfect during the night.