The Pivotal Roles of Light and Ca‐Doping in Photothermocatalytic CO₂ Reduction by Methane on Nanocomposites of Nickel Nanoparticles Loaded on Ca‐Doped Al₂O₃

Abstract

CO2 and CH4 are greenhouse gases that can be converted into H2 and CO through light‐driven photothermocatalytic CO2 reduction with methane (CRM), which is a process of solar energy collection and storage. However, conventional catalysts require high light intensities (≥192.0 kW m−2) to obtain high fuel reaction rates and solar‐to‐fuel efficiency (η), and deactivate easily to coking at high temperature. Herein, a nanomaterial of Ni nanoparticles loaded on Ca‐doped Al2O3 (Ni/Ca–Al2O3) is synthesized. Ca doping improves the CO2 adsorption capacity of Ni/Ca–Al2O3. Under focused ultraviolet–visible–infrared illumination at low light intensity (80.8 kW m−2), Ni/Ca–Al2O3 obtains high production rates of H2 (, 76.85 mmol min−1 g−1) and CO (rCO, 90.90 mmol min−1 g−1), which are 1.9 and 1.3 times of those in the dark respectively, and exhibits a large η (30.3%) and good stability. The coking rate of Ni/Ca–Al2O3 is reduced by a factor of 25.8 compared to the reference catalyst with Ni nanoparticles loaded on Al2O3. The improvement of catalytic activity and anticoking properties stems from the photoactivation, which not only accelerates the CRM on Ni nanoparticles, but also enhances the oxidation of carbon species (produced on Ni nanoparticles) through strong adsorption of CO2 on Ca–Al2O3 at Ni/Ca–Al2O3 interface.