Pd-Doped Tin Oxide Nanostructured Catalysts for Electrochemical Reduction of Carbon Dioxide

Electrocatalytic reduction of CO2 can convert CO2 into a variety of carbon-based fuels and achieve carbon neutrality. Tin oxide (SnO2) electrocatalytic materials have the advantages of low cost and low toxicity, and the electrocatalytic reduction of CO2 to formic acid is highly selective. In this paper, Pd-doped SnO2 nanoparticle materials were synthesized by flame spray pyrolysis and their properties for electrocatalytic reduction of CO2 to formic acid were explored in a gas diffusion electrolytic cell. The results showed that the Pd/SnO2 catalysts could improve the catalytic activity for the conversion of CO2 to formate, and the most superior 0.5 Pd/SnO2 showed a Faraday efficiency of 63% for formate at - 1.20 V vs. RHE and a current density of 90.59 mA.cm-2, which were 1.4 and 2.7 times higher than that of pure SnO2, respectively. The modified catalyst grains were refined, and the charge transfer resistance at the catalyst interface was reduced, and the electrochemically active area was increased, generating more catalytically active sites and increasing the contact between CO2, electrolyte, and electrode-catalyst. Density functional theory calculations showed that the doping of Pd element changed the local structure of SnO2, and the Pd/SnO2 surface was more favorable for the generation of the intermediate products *HCOO- and formate as well as the inhibition of hydrogen precipitation, which was consistent with the experimental results.