Surface chemistry imposes selective reduction of CO2 to CO over Ta3N5/LaTiO2N photocatalyst

Abstract

Understanding the mechanism underlying photocatalytic product selectivity will provide valuable guidance in developing novel catalysts and reaction pathways. In this article, the role of surface chemistry in product generation is well-demonstrated using LaTiO₂N, Ta₃N₅, and their hybrids with dominant (002) and (020) facets, respectively. Photocatalytic test results show that CO₂ could be reduced to CH₄ and CO in the presence of LaTiO₂N and Ta₃N₅ photocatalysts, respectively. The detected intermediates suggest that the reaction pathway could possibly be . Product selectivity is dependent on the ability to capture CO onto the photocatalyst surface, which is probably related to the electronegativity of the adsorption sites. Strong adsorption of CO on the LaTiO₂N surface favors the subsequent hydrogenation reaction to generate CH₄, while weak CO adsorption on Ta₃N₅ results in CO as the main product of CO₂ reduction, which is demonstrated by theoretical calculations as well. Such product selectivity is mainly related to the surface chemistry of the photocatalyst and independent of the surface charge concentration. Our results provide a progressive understanding of selective product formation during photocatalytic CO₂ reduction.