Electrocatalytic property of Zn-Al layered double hydroxides for CO2 electrochemical reduction

Electrocatalytic CO2 reduction reaction (CO2RR) has attracted considerable attention as a technology to recycle carbon dioxide (CO2) into raw materials for chemicals using renewable energies. In this study, the electrocatalytic CO2RR activity of Zn-Al layered double hydroxides (LDHs) was studied. Zn-Al LDHs loaded carbon sheets were prepared, and CO2 RR was performed using CO2-saturated KHCO3 electrolyte to confirm the catalytic ability of Zn-Al LDH. Zn-Al LDHs intercalated with CO32− anion were synthesized using the mixture of metal nitrates with the different molar ratio of Zn2+/Al3+ by the co-precipitation process, whose corresponding products were named as Zn2Al1 LDH, Zn3Al1 LDH, and Zn4Al1 LDH, respectively. Except for Zn2Al1 LDH, ZnO was observed to exist as an impurity. The synthesized Zn-Al LDHs exhibited the electrocatalytic CO2RR activity for CO formation. In the case of the Zn2Al1 LDH, the current density of 15 mA cm−2 was obtained with 77% selectivity for CO and 94% selectivity for (CO + H2) at − 1.4 V vs. RHE. Furthermore, Zn3Al1 and Zn4Al1 LDHs showed a significant change relating to ZnO impurities in the XRD patterns and SEM images before and after the CO2RR whereas Zn2Al1 LDH did not show it. These results indicate that Zn-Al LDH is promising as a CO2RR electrocatalyst for CO formation.