A novel nanocomposite of mesoporous silica supported Ni nanocrystals modified by ceria clusters with extremely high light-to-fuel efficiency for UV-vis-IR light-driven CO2 reduction

Abstract

A novel nanocomposite of mesoporous silica supported Ni nanocrystals modified by ceria clusters was synthesized by a facile approach. The nanocomposite exhibits high photothermocatalytic activity for CO₂ reduction by CH₄ to produce CO and H₂ (CRM) under focused UV-visible-infrared illumination without using any additional heater. Extremely high H₂ and CO production rates (33.42 and 41.53 mmol min⁻¹ g⁻¹) as well as an extraordinarily high light-to-fuel efficiency of 27.4% are achieved. The nanocomposite also has efficient CRM photothermocatalytic activity even under focused λ > 690 nm visible-infrared illumination. It is discovered that the ceria cluster modification of Ni nanocrystals markedly improves the photothermocatalytic activity and durability. The excellent CRM photothermocatalytic activity is ascribed to highly effective light-driven thermocatalytic CRM due to the photothermal conversion across the entire solar spectrum and good CRM thermocatalytic activity of the nanocomposite. A novel photoactivation is discovered to markedly enhance the light-driven thermocatalytic activity. Based on the experimental results of TG-MS, XRD, TEM, in situ FTIR spectroscopy, Raman spectroscopy, and isotope labelling together with the DFT calculations, we reveal the origin of the markedly enhanced photothermocatalytic activity and durability as well as the novel photoactivation. Oxygen of ceria clusters in the nanocomposite participates in CRM on Ni nanocrystals, which markedly decreases the activation energies of the oxidation of C* and CH* species as CRM dominant steps. The focused illumination considerably reduces the activation energy of CRM on the nanocomposite, thus markedly enhancing the photothermocatalytic activity.