Significant improvement in activity, durability, and light-to-fuel efficiency of Ni nanoparticles by La2O3 cluster modification for photothermocatalytic CO2 reduction

Abstract

A novel nanocomposite of La2O3 cluster modified Ni nanoparticles loaded on mesoporous silica (Ni-La2O3/SiO2) was synthesized. Under focused UV–vis-IR irradiation, Ni-La2O3/SiO2 exhibits high production rates of CO (rCO) and H2 (rH2) (42.90 and 38.11 mmol min−1 g−1) for photothermocatalytic CO2 reduction by CH4 (CRM). A high light-to-fuel efficiency (η) of 20.3 % is achieved. Ni-La2O3/SiO2 also exhibits excellent photothermocatalytic durability. Its photothermocatalytic activity almost remains unchanged after reacted for 90 h. It is found for the first time that the photothermocatalytic activity, durability, and η value of Ni nanoparticles are substantially promoted by the La2O3 cluster modification. The results of TG-MS, TEM, XRD, isotope labelling experiment using 12CH4 and 12C18O2 as reactants, and Raman show that oxygen of La2O3 clusters in Ni-La2O3/SiO2 takes part in oxidization of carbon species formed by CH4 dissociation. This causes a substantial reduction in carbon deposition rate, thus promoting the catalytic activity and durability. It is found that the focused irradiation substantially decreases the apparent activation energy of CRM on Ni-La2O3/SiO2, thus promoting the catalytic activity. The new photoactivation also restrain CO disproportionation as major side-reaction of carbon deposition, thus decreasing the rate of carbon deposition.