CO2 Electroreduction on Unsupported PdPt Aerogels: Effects of Alloying and Surface Composition on Product Selectivity

Due to its unique ability to reduce carbon dioxide (CO2) into CO or formate at high versus low overpotentials, respectively, palladium is a promising catalyst for the electrochemical CO2-reduction reaction (CO2RR). Further improvements aim at increasing its activity and selectivity toward either of these value-added species, while reducing the amount of hydrogen produced as a side product. With this motivation, in this work, we synthesized a range of unsupported, bimetallic PdPt aerogels and pure Pt or Pd aerogels and extensively characterized them using various microscopic and spectroscopic techniques. These revealed that the aerogels' porous web consists of homogenous alloys of Pt and Pd, with palladium and platinum being present on their surface for all compositions. The subsequent determination of these aeorgels' CO2RR performance unveiled that the high activity of these Pt surface atoms toward hydrogen evolution causes all PdPt alloys to favor this reaction over CO2 reduction. In the case of the pure Pd aerogel, although, its unsupported nature leads to a suppression of H-2 evolution and a concomitant increase in the selectivity toward CO when compared to a commercial, carbon-supported Pd-nanoparticle catalyst.

Automated summary

Palladium is a promising catalyst for the electrochemical CO2-reduction reaction (CO2RR) due to its unique ability to reduce carbon dioxide into CO or formate at high overpotentials. This research focuses on the synthesis and characterization of unsupported bimetallic PdPt and pure Pt or Pd aerogels. The results show that the Pt surface atoms have high activity toward hydrogen evolution, leading to a preference for this reaction over CO2 reduction in all PdPt alloys. However, the pure Pd aerogel exhibits increased selectivity toward CO due to the suppression of hydrogen evolution caused by its unsupported nature.