A two-pronged strategy to enhance visible-light-driven overall water splitting via visible-to-ultraviolet upconversion coupling with hydrogen-oxygen recombination inhibition

Abstract

Visible-light-driven overall splitting water is a potential and sustainable approach for hydrogen generation. Although many photocatalysts have been reported to be active for this reaction, the efficiency of overall splitting water is still quite low. In this work, a two-pronged strategy is adopted to overcome two key restrictions on visible-light-driven photocatalytic overall water splitting by taking advantages of visible-to-ultraviolet upconversion (UC) effect as well as inhibiting hydrogen-oxygen recombination reaction over the photocatalyst. In order to realize that purpose, a composite photocatalyst with high stability was designed by assembling three components consisting of visible-to-ultraviolet UC Pr3+-Y2SiO5, UV-responsive semiconductor photocatalyst CaTiO3 and perfluorodecalin as an oxygen transfer regent. By the first strategy, the visible-to-ultraviolet UC unit is capable of converting visible irradiation to UV light emission, which effectively excites UV-responsive photocatalyst CaTiO3. The photocatalytic activity has been raised up to 200% by regulating the amount of visible-to-ultraviolet UC Pr3+-Y2SiO5 in the designed composite photocatalyst Pr3+-Y2SiO5/CaTiO3. The photocatalyst exhibited high photochemical stability and catalytic stability in four recycle reactions. By the second strategy, hydrogen and oxygen recombination on photocatalyst surface has been effectively inhibited by an oxygen transfer reagent FDC to capture and take away newly generated oxygen from catalyst surface. This two-pronged strategy is not only convenient and efficient, but exhibits potential versatility for the most stable UV-responsive semiconductor photocatalysts to realize overall split water by visible light irradiation.