Effect of the chloride ion as a hole scavenger on the photocatalytic conversion of CO2 in an aqueous solution over Ni–Al layered double hydroxides

Abstract

The photocatalytic conversion of CO₂ into useful chemical compounds in water without using organic sacrificial reagents is a promising method to overcome environmental and energy problems. Various synthesized layered double hydroxides (LDHs) are capable of reducing CO₂ to CO in an aqueous solution under UV light irradiation. However, it is difficult to oxidize H₂O to O₂ in a photocatalytic system using LDHs as photocatalysts. In this study, we investigated the photocatalytic conversion of CO₂ using a Ni–Al LDH in an aqueous solution of NaCl. Hypochlorous acid (HClO) was produced as an oxidation product of Cl⁻ with the formation of reduction products such as CO and H₂ under photoirradiation. We propose the inclusion of Cl⁻ in the reaction solution to be one of the most promising ways for obtaining a hole scavenger, an approach that would enable the construction of an artificial photosynthesis system for the conversion of CO₂.