Production of CH4 and CO on CuxO and NixOy coatings through CO2 photoreduction

Abstract

CO2 capture and photocatalytic reduction to hydrocarbons is an interesting yet challenging area that requires photocatalysts with the capability to capture and photoconvert CO2 simultaneously. Furthermore, earth-abundant photocatalysts with high efficiency and product selectivity are essential for commercialization. Thus, two earth-abundant photocatalysts based on copper and nickel oxides were selected to produce solar fuels from CO2 photoreduction. The photocatalysts were immobilized on commercial glass fibers substrates by a facile one-step microwave-hydrothermal method. CuxO (x = 1, 2) and NixOy (x = 1, 2 and y = 1, 3) coatings on glass fiber were evaluated as photocatalysts in two different reactors to investigate the selectivity in a continuous reactor and a batch system. Two different light sources were employed: a heterochromatic lamp to simulate part of the solar light in the continuous reactor and a LED visible light in the batch reactor. CuO/Cu2O photocatalysts exhibited a selective production of CH4 (95 µmol g−1 h−1) and CH3OH (177 µmol g−1 h−1) from CO2 photoreduction in the continuous and batch continuous systems, respectively. The superior performance was attributed to the unique rod-shape morphology, the presence of oxygen vacancies, and efficient charge transfer in the CuO/Cu2O heterostructure with high affinity towards CO2, resulting the formation of mono- and bidentate carbonate species during the CO2 photoreduction reaction. NixOy coating with 2D cubic shape produced CO (103 µmol g−1 h−1) and HCOOH (4245 µmol g−1 h−1), associating with the low CO2 affinity and less efficient charge separation compared to CuO/Cu2O heterostructure.