Highly Efficient Photothermocatalytic CO 2 Reduction in Ni/Mg‐Doped Al 2 O 3 with High Fuel Production Rate, Large Light‐to‐Fuel Efficiency, and Good Durability

A novel nanocomposite of Ni nanoparticles loaded on Mg‐doped Al 2 O 3 (Ni/Mg‐Al 2 O 3 ) was prepared. By photothermocatalytic CO 2 reduction with methane (CRM) merely using focused UV‐vis‐IR illumination on Ni/Mg‐Al 2 O 3 , high production rates of H 2 ( r H 2 , 69.71 mmol min −1  g −1 ) and CO ( r CO , 74.57 mmol min −1  g −1 ) and an extremely large light‐to‐fuel efficiency (η, 32.9%) are acquired. High r H 2and r CO (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‐Al 2 O 3 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 Al 2 O 3 . The enormous carbon deposition inhibition is ascribed to the presence of a fence of CO 2 molecules (strongly adsorbed on Mg‐doped Al 2 O 3 ) around Ni nanoparticles, which block the polymerization and growth of carbon species to nanofibers by promoting the oxidation of carbon species formed by CH 4 dissociation. The high photothermocatalytic activity of Ni/Mg‐Al 2 O 3 arises from efficient light‐driven thermocatalytic CRM. A photoactivation is found to considerably raise the photothermocatalytic activity of Ni/Mg‐Al 2 O 3 because of the apparent activation energy ( E a ) being substantially decreased upon focused illumination. The E a reduction is associated with the rate‐determining steps of CRM (e.g., CH 4 dissociation and the oxidation of carbon species) being accelerated upon focused illumination.