ZrO₂ Aerogel-Supported Pd Nanoparticles for Photothermal CO₂ Reduction

Decarbonizing chemical processes requires sustainable heat sources that can replace fossil-derived fuels and feedstocks. In photothermal catalysis, heat is supplied by converting light directly on the catalyst surface. This direct heating eliminates the need for external heat sources and exchangers and enables efficient use of solar or LED light sources. Aerogel-supported catalysts are particularly effective for photothermal applications due to their combination of transparency, low thermal conductivity, and high surface area, which allow deep light penetration and minimal heat loss. Using a scalable wet-impregnation approach, palladium (Pd) was deposited on aerogel granules composed of zirconia (ZrO₂) nanocrystals. The nanocrystals were gelled and shaped into spherical granules. Negatively charged palladium-ethylenediaminetetraacetic acid (Pd-EDTA) complexes were adsorbed onto the positively charged gel surface, followed by supercritical drying, calcination, and reduction under hydrogen to form well-dispersed Pd nanoparticles. Under 4.8 W cm^-2 concentrated white LED illumination, the Pd/ZrO₂ aerogel reached temperatures up to 300°C, driving carbon dioxide (CO₂) reduction to carbon monoxide (CO) with ∼96% selectivity. Co-deposition of indium (In) stabilized the catalytic activity and increased CO selectivity above 99%. Compared to powdered catalysts of the same composition, the PdIn/ZrO₂ aerogel spheres produced ∼four times more CO, highlighting the combined benefit of efficient light absorption and low thermal conductivity.