Highly Efficient Photothermocatalytic CO2 Reduction in Ni/Mg‐Doped Al2O3 with High Fuel Production Rate, Large Light‐to‐Fuel Efficiency, and Good Durability

Abstract

A novel nanocomposite of Ni nanoparticles loaded on Mg‐doped Al2O3 (Ni/Mg‐Al2O3) was prepared. By photothermocatalytic CO2 reduction with methane (CRM) merely using focused UV‐vis‐IR illumination on Ni/Mg‐Al2O3, high production rates of H2 (, 69.71 mmol min−1 g−1) and CO (rCO, 74.57 mmol min−1 g−1) and an extremely large light‐to‐fuel efficiency (η, 32.9%) are acquired. High and rCO (51.07 and 59.66 mmol min−1 g−1) and a large η (32.5%) are acquired even by using focused λ > 560 nm vis‐IR illumination. Ni/Mg‐Al2O3 shows good durability for photothermocatalytic CRM due to the side reaction of carbon deposition being enormously inhibited in comparison with a reference catalyst of Ni nanoparticles loaded on Al2O3. The enormous carbon deposition inhibition is ascribed to the presence of a fence of CO2 molecules (strongly adsorbed on Mg‐doped Al2O3) around Ni nanoparticles, which block the polymerization and growth of carbon species to nanofibers by promoting the oxidation of carbon species formed by CH4 dissociation. The high photothermocatalytic activity of Ni/Mg‐Al2O3 arises from efficient light‐driven thermocatalytic CRM. A photoactivation is found to considerably raise the photothermocatalytic activity of Ni/Mg‐Al2O3 because of the apparent activation energy (Ea) being substantially decreased upon focused illumination. The Ea reduction is associated with the rate‐determining steps of CRM (e.g., CH4 dissociation and the oxidation of carbon species) being accelerated upon focused illumination.