Regulating divalent metal species in aluminum-based layered double hydroxides to selectively promote photocatalytic CO production from CO2

The results indicate that Zn component can reduce the charge transfer resistance of Al-based LDHs, which leads to a higher photo-generated current density, thus achieving a high CO2 reduction performance. [Display omitted] •The Zn component can reduce the charge transfer resistance of Al-based LDHs.•The ZnAl-LDH presents a higher yield and selectivity of CO product than MgAl-LDH and NiAl-LDH.•The strategy of regulating divalent metal species can construct advanced LDH-based photocatalyts. Photocatalysis is a potential technology to reduce CO2 greenhouse gases. Layered double hydroxides (LDHs) are promising photocatalysts due to good catalytic activity, low synthesis cost, and large-scale preparation. However, their CO selectivity in photocatalytic CO2 reduction is still unsatisfactory. Herein, we have systematically studied the effects of different divalent metal species (e.g., Mg2+, Ni2+, and Zn2+) on the CO selectivity in aluminum-based LDHs. The results indicate that ZnAl-LDH can negatively shift the conduction band to obtain a large driving power for CO2 reduction to CO, which much improves the CO selectivity. In addition, the ZnAl-LDH also reduces the charge transfer resistance leading to a higher photo-generated current density, thus achieving a high CO2 reduction performance. Specifically, ZnAl-LDH presents a better CO selectivity of 72.8 % and a higher CO yield of 1.58 μmol·g−1·h−1, than MgAl-LDH (66.2 %, 0.96 μmol·g−1·h−1) and NiAl-LDH (59.8 %, 1.01 μmol·g−1·h−1). This study provides a feasible strategy to improve the selectivity of CO photocatalytic reduction of CO2 by regulating divalent metal species in aluminum-based layered double hydroxides.