Promoting the reduction of CO₂ to formate and formaldehyde via gas-liquid interface dielectric barrier discharge...

A Zn_0.5Cd_0.5S (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.