UV-Vis-IR irradiation driven CO2 reduction with high light-to-fuel efficiency on a unique nanocomposite of Ni nanoparticles loaded on Ni doped Al2O3 nanosheets

A unique nanocomposite of Ni nanoparticles loaded on Ni doped Al2O3 nanosheets (Ni/Ni-Al2O3) was prepared with a facile approach. Ni/Ni-Al2O3 possesses very high photothermocatalytic activity for CO2 reduction with CH4 (CRM) under the focused UV-Vis-IR irradiation. Its production rates of H2 and CO (rH2 and rCO) are 27.02 and 28.71 mmol g-1 min-1, respectively. A very high light-to-fuel efficiency (η) of 19.9% is achieved. Even under the focused Vis-IR irradiation of λ > 690 nm, it still possesses photothermocatalytic performance, evidenced by its high rH2 and rCO values (14.64 and 17.24 mmol g-1 min-1) as well as high η value of 16.4%. Ni/Ni-Al2O3 possesses excellent photothermocatalytic durability much superior to its counterpart of Ni nanoparticles loaded on Al2O3 nanosheets (Ni/Al2O3). This is ascribed to the synergetic effect between Ni nanoparticles and Ni doped Al2O3 in Ni/Ni-Al2O3 in which oxygen in Ni doped Al2O3 participates in the oxidation of the formed carbon species, thus inhibiting carbon deposition on Ni nanoparticles. The high photothermocatalytic activity of Ni/Ni-Al2O3 originates from effective light-driven thermocatalytic CRM. A new photoactivation is discovered to substantially reduce the activation energy for CRM on Ni/Ni-Al2O3, thus considerably enhancing the light-driven thermocatalytic activity. Moreover, the new photoactivation also substantially inhibits the side reaction of CO disproportionation, thus promoting the photothermocatalytic durability due to the carbon deposition being substantially reduced.