ZnO-modified cobalt single-atom catalyst enhanced CO2-to-CO electroreduction via interfacial proton transfer

In order to address issues of proton shortage for key intermediate *COOH formation during CO 2 -to-CO catalytic electroreduction, ZnO was used to modify cobalt single-atom (SA) active sites to enhance interfacial proton transfer for improving CO conversion. ZnO-Co SAs/NC(O) composite catalyst was synthesized by anchoring ZnO with oxygen-containing functional groups on oxygen-treated nitrogen-doped graphene with Co single atoms (Co SAs/NC(O)) via in-situ chemical deposition. X-ray photoelectron spectroscopy confirmed ZnO loading on graphene via Zn-O-C bonds. Spherical aberration-corrected electron microscope images showed uniform dispersion of Co single atoms around ZnO nanoparticles. In-situ ATR-FTIR indicated that ZnO loading enhanced interfacial water activation, thereby promoting key intermediate *COOH formation. Density functional theory calculations suggested that ZnO promoted proton generation through water splitting, reducing energy barrier of rate-determining step for *COOH formation by 0.12 eV. The CO Faradaic efficiency over 40 wt% ZnO-Co SAs/NC(O) catalyst reached 95.63% at −1.0 V (vs. RHE), which was much higher than that of Co SAs/NC(O) catalyst (82.23%).