The mechanism of photocatalytic CO2 reduction by graphene-supported Cu2O probed by sacrificial electron donors

[EN] Cu2O nanoparticles of 5 nm average size have been adsorbed (1.74 wt% loading) on defective graphene (Cu2O/G) previously obtained by the pyrolysis of alginic acid sodium salt. The Cu2O crystal phase was determined by XRD. XPS shows that the external layers of the Cu2O nanoparticles are constituted mainly of Cu+ although a certain percentage of CuII+ was also present. Cu2O/G is a photocatalyst for the CO2 reduction to methane in the presence of sacrificial agents, and the rate of CH4 production depends on the oxidation potential of the electron donor. This relationship supports a mechanism involving photo-induced charge separation with the generation of electrons and holes. The highest CH4 formation rate upon UV-Vis irradiation of Cu2O/G with a 300 W Xe lamp was achieved for dimethylaniline reaching 326 mu mol CH4 per g per h. The spectral response of the Cu2O photocatalyst shows, however, that the response of the photocatalyst is mainly due to UV irradiation, indicating that light absorption at the low Cu2O loading on the Cu2O/G photocatalyst occurs mainly on the graphene component.Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa SEV2016-0683, GRAPAS, and CTQ2015-69563-CO2-R1) and the Generalitat Valenciana (Prometeo 2015-083) is gratefully acknowledged. J. A. thanks the Universitat Politecnica de Valencia for a postdoctoral scholarship. D. M. also thanks the Spanish Ministry of Science for the PhD scholarship.Mateo-Mateo, D.; Asiri, AM.; Albero-Sancho, J.; García Gómez, H. (2018). The mechanism of photocatalytic CO2 reduction by graphene-supported Cu2O probed by sacrificial electron donors. Photochemical & Photobiological Sciences. 17(6):829-834. https://doi.org/10.1039/c7pp00442gS82983417