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

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 H-2 (rH2, 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 (eta, 32.9%) are acquired. High rH2 and r(CO) (51.07 and 59.66 mmol min(-1) g(-1)) and a large eta (32.5%) are acquired even by using focused lambda > 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 (E-a) being substantially decreased upon focused illumination. The E-a 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.

Automated summary

The novel nanocomposite of Ni nanoparticles loaded on Mg-doped Al2O3 (Ni/Mg-Al2O3) exhibits high production rates of H-2 and CO in photothermocatalytic CO2 reduction with methane, along with extremely large light-to-fuel efficiency, attributed to the inhibition of carbon deposition and efficient light-driven thermocatalytic reaction.