Promoting the reduction of CO2 to formate and formaldehyde via gas–liquid interface dielectric barrier discharge using a Zn0.5Cd0.5S/CoP/multiwalled carbon nanotubes catalyst

A Zn0.5Cd0.5S (ZCS) solid solution was prepared using a hydrothermal method, in which CoP nanowires were added as a co-catalyst and co-deposited with multiwalled carbon nanotubes (MWNTs) on sponge to prepare a series of ZCS/CoP/MWNTs/sponge electrodes. The microstructures of catalysts were analyzed to confirm ZCS and CoP were successfully loaded in MWNTs/sponge. The CO2 reduction products (formate and formaldehyde) produced via dielectric barrier discharge (DBD) using the different catalysts proved that the introduction of the CoP nanowires co-catalyst can enhance the catalytic activity of ZCS/MWNTs/sponge in the DBD system. Using 10% CoP and a ZCS/CoP concentration of 2.5 g·L-1, the resulting ZCS/CoP/MWNTs/sponge catalyst exhibited the best catalytic of CO2 reduction ability toward formate (7894.6 μmol·L-1) and formaldehyde (308.5 μmol·L-1) after 60 min of discharge, respectively. The proposed DBD catalytic mechanism for the reduction of CO2 was analyzed according to the Tafel slope, density functional theory calculations, photocurrent density and plasma reaction process. Furthermore, the application of the DBD catalytic technology for CO2 capture and reduction was shown to be efficient in a seawater system, and as such, it could be useful for marine CO2 storage and conversion.