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

Abstract

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 focused UV-vis-IR irradiation. Its production rates of H₂ and CO (r_H2 and r_CO) 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 focused vis-IR irradiation of λ > 690 nm, it still possesses photothermocatalytic performance, evidenced by its high r_H2 and r_CO values (14.64 and 17.24 mmol g⁻¹ min⁻¹) and a high η value of 16.4%. Ni/Ni–Al₂O₃ possesses excellent photothermocatalytic durability which is 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 type of 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 CO disproportionation side reaction, thus promoting the photothermocatalytic durability due to carbon deposition being substantially reduced.