Pd doped tin oxide nanostructured catalysts for electrochemical reduction of carbon dioxide

Abstract 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.