Pd–Sn Alloy Electrocatalysts for Interconversion Between Carbon Dioxide and Formate/Formic Acid

Pd–Sn alloy catalysts, fabricated using a coelectrodeposition method, were used for the interconversion of carbon dioxide and formate/formic acid. The morphologies and compositions of the Pd–Sn alloy catalysts were controlled by changing the Sn precursor concentration in the deposition bath. The as-prepared catalysts exhibited bifunctional catalytic activities in both formic acid oxidation and carbon dioxide reduction. By increasing Sn content in the Pd–Sn alloy catalyst, its catalytic activity was enhanced in carbon dioxide reduction, but diminished in formic acid oxidation. The stability of the catalyst was poor because of the highly positive potential range in which formic acid oxidation occurs. After the annealing process, both bifunctional activity and stability in formic acid oxidation were improved. Among the alloys, H₂-annealed Pd₄₅Sn₅₅ alloy was the most suitable catalyst for unitized regenerative fuel cells based on carbon dioxide and formate/formic acid, because of its bifunctional activity, stability, and tolerance of carbon monoxide poisoning.