Accelerating CO2 Electroreduction to CO Over Pd Single-Atom Catalyst

The electrochemical conversion of carbon dioxide (CO2) into value-added chemicals is regarded as one of the promising routes to mitigate CO2 emission. A nitrogen-doped carbon-supported palladium (Pd) single-atom catalyst that can catalyze CO2 into CO with far higher mass activity than its Pd nanoparticle counterpart, for example, 373.0 and 28.5 mA mg(Pd)(-1), respectively, at -0.8 V versus reversible hydrogen electrode, is reported. A combination of in situ X-ray characterization and density functional theory (DFT) calculation reveals that the Pd-N-4 site is the most likely active center for CO production without the formation of palladium hydride (PdH), which is essential for typical Pd nanoparticle catalysts. Furthermore, the well-dispersed Pd-N-4 single-atom site facilitates the stabilization of the adsorbed CO2 intermediate, thereby enhancing electrocatalytic CO2 reduction capability at low overpotentials. This work provides important insights into the structure-activity relationship for single-atom based electrocatalysts.