Photocatalytic reduction of CO2 over LaMO3 (M: Fe, Co, Mn) /CuxO films

Abstract LaMO3/CuxO (M: Co, Mn, Fe) thin films were prepared in two steps. First, lanthanum perovskites were deposited by spin coating, and then a CuxO layer by Chemical Vapor Deposition. The X-ray diffraction characterization confirmed the formation of the crystalline perovskite phases. The topography of the films was observed by AFM analysis, where fine needles grains appeared in LaMnO3/CuxO and LaCoO3/CuxO perovskite films, being attributed to the CuxO layer. XPS characterization confirms the presence of a larger concentration of oxygenated species over the surface of the films; besides, it was possible to elucidate a mixed-valence state of copper nanoparticles. DR UV–vis analyses show a redshift displacement for LaCoO3 and LaMnO3 films with the addition of copper nanoparticles, related to improved light absorption. The evaluation of the CO2 photoreduction using the pure perovskite films was performed. The reaction showed that adsorbed oxygenated species (CO32−, OH−, among others) over the surface could hinder active sites causing low performance. Once films were decorated with CuxO nanoparticles, their performance was improved significantly in the formic acid evolution. Copper nanoparticles acted like active sites for CO2 reduction, promoting the separation of the charges. LaMnO3/CuxO films presented the higher production of formic acid associated with low presence of oxygenated species in the surface and the formation of scheme Z between semiconductors, allowing a better charge transfer.