Durable Electrocatalytic CO₂ Reduction Using Intermetallic Compound PdIn Nanoparticles and Their Application to a Solar Energy Harvesting System

The development of electrocatalysts capable of reducing CO2 to carbonous compounds, such as CO and HCOOH, has received much attention as one of the fundamental research topics for establishing a CO2 utilization technology using renewable energies such as solar energy. Our study demonstrates that intermetallic compound (IMC) PdIn nanoparticles are electrocatalysts with the potential to achieve artificial photosynthetic CO2 reduction using such renewable energy. Under simulated solar light, it also demonstrates artificial photosynthetic CO2 reduction using a photoelectrochemical cell combining a PdIn/KB electrocatalyst as the cathode part with a CoOx-loaded BiVO4:Mo (BiVO4 doped with Mo cations) photoanode in an aqueous electrolyte. The applied voltage was 1.20 V less than the theoretical voltage for water splitting and CO2 reduction using water as an electron donor. Although Pd-based nanoparticle electrocatalysts promote electrochemical CO2 reduction at a lower overpotential, most of them are readily poisoned by CO, which is formed as the reduction product in the electrochemical CO2 reduction. In contrast, nanoparticulate IMC PdIn formed by alloying Pd with In combined both the activity for the electrochemical CO2 reduction and a significant durability to CO poisoning. This was revealed through control experiments by intentionally dosing CO into the electrolyte and density functional theory calculations to estimate the CO adsorption energy on the surfaces.