Photothermal catalytic activity of combustion synthesized LaCoxFe1−xO3 (0 ≤ x ≤ 1) perovskite for CO2 reduction with H2O to CH4 and CH3OH

A range of LaCoxFe1−xO3 perovskites with different Co-doping at the B-site were successfully synthesized via a sol–gel combustion route. Phase pure samples were obtained by calcination at 700 °C for 2 h. The morphology, crystal structure, surface area, band structures, oxygen vacancies and catalytic properties of each analog were characterized in detail. The band structures and oxygen vacancies of the catalysts were changed by adjusting the dopant concentration. The catalytic performance of the LaCoxFe1−xO3 materials was characterized using water as a hydrogen source in the production of CH4 and CH3OH from CO2. Under photothermal conditions, 350 °C with a visible light source equipped with 420 nm cut filter, it was found that x value will influence the total yield and the solar to CH4 and CH3OH energy conversion efficiency significantly. For x = 0.6 compound, the production of CH4 and CH3OH evolution can reach 437.28 and 13.75 μmol g−1 in 6 h, which were 3.2 and 4.0 times that of LaFeO3 under the same condition. The overall solar-to-methane efficiency and solar-to-methanol efficiency for LaCo0.6Fe0.4O3 were 0.603%, 0.019% and for LaFeO3 were 0.191%, 0.005% in the photothermal mode, respectively. The results show that the band gap energy is correlated with the photothermal activity and the LaCo0.6Fe0.4O3 has the position of the CB and VB more suitable for CO2 reduction. The CB and VB value of LaCo0.6Fe0.4O3 were −0.258 and +1.422 V and CO2 (−0.24 V for CB) can be reduced to methane under the conditions.