Photothermal synergic enhancement of direct Z-scheme behavior of Bi4TaO8Cl/W18O49 heterostructure for CO2 reduction

Abstract All-solid-state Z-scheme systems are attracting increasing interest in artificial photosynthesis of solar fuel. Recent research has revealed that solid electron mediators facilitate shuttle of electrons and thereby enhance photocatalytic activity. However, for a mediator-free direct Z-scheme system, it still remains a challenge to promote the Z-scheme-type charge transfer at the interface. Herein, we report that the photocatalytic reduction of CO2 over the direct Bi4TaO8Cl/W18O49 (BiW) Z-scheme system, which is assembled from Bi4TaO8Cl nanosheet and nanosized W18O49, is markedly enhanced by simple integration of the photocatalytic process with external heating. The CO yield over a typical BiW Z-scheme system is increased by 87 times when the system temperature is increased from 298 K to 393 K. This yield via BiW photocatalysis at 393 K is higher than Bi4TaO8Cl photocatalysis at 298 K by a factor of 167. The superior performance of BiW Z-scheme system at elevated temperature is believed to result from the thermo-enhanced shuttle of electron from W18O49 to Bi4TaO8Cl. Moreover, this BiW Z-scheme enables long-lasting catalytic reduction of CO2 in the dark after light irradiation, benefiting from the thermal release of stored electrons in W18O49 to the conduction band of Bi4TaO8Cl. This study suggests that photothermal synergy can enhance the Z-scheme behavior, providing a promising means for designing photothermal catalysts for the solar-catalytic reduction of CO2 to fuel.