Facile construction of BiOBr/CoAl-LDH heterojunctions with suppressed Z-axis growth for efficient photoreduction of CO2

• BiOBr/CoAl-LDH heterojunctions with suppressed Z-axis growth were prepared. • The closely contact between heterojunctions were proved. • A highly CO 2 photoreduction performance was achieved. • The deep mechanism during the photocatalytic reaction was investigated. Due to the massive usage of fossil fuels, the carbon dioxide content in the atmosphere is increasing year by year. Meanwhile, the CO 2 photoreduction has been widely researched and regarded as a promising method to utilize the CO 2 . BiOBr has good photocatalytic activity as a suitable photocatalyst. However, the photocatalytic performance is still unsatisfactory, and the product of CO 2 photocatalytic reduction has a large proportion of CO instead of CH 4 . Therefore, in this paper, we prepare ultrathin CoAl-LDH by inhibiting Z-axis growth and load ultrathin CoAl-LDH on BiOBr to construct heterojunction to improve the photocatalytic efficiency of BiOBr and regulate the selectivity of the products. It was found that the loading of ultrathin CoAl-LDH helps to improve the photogenerated electron-hole pair separation ability and photogenerated carrier transport ability, thus improving the photocatalytic performance. At the same time, the loading of ultrathin CoAl-LDH helps to convert the photocatalytic CO 2 reduction product from CO to CH 4 . After the gradient study experiment on the dosage of ultrathin CoAl-LDH, it was found that the best effect was achieved at the dosage of 10 mL of ultrathin CoAl-LDH colloidal solution, and the CO yield rate was 4.096 μmol·g -1 ·h -1 and CH 4 yield rate was 4.174 μmol·g -1 ·h -1 . Meanwhile, the CH 4 selectivity will reach 46% of the product. In this work, we offer a novel regulation strategy for selectivity improvement of CO 2 photocatalytic reduction, which can be assigned to the moderated ultrathin CoAl-LDH loading, thus enhance the selectivity of CO 2 to CH 4 .