Insights into the role of CuO in the CO2 photoreduction process

The CO 2 photoreduction process to produce light hydrocarbons is known to be influenced by the presence of CuO nanoparticles, but the actual role of this material, whether as a catalyst or a reactant, has not yet been revealed. In this work, we investigate the role of CuO nanoparticles produced by a solvothermal method as a catalyst in CO 2 -saturated water reaction media under UV light, considering the effects of different electrolytes (Na 2 C 2 O 4 , KBrO 3 , and NaOH) and temperatures on nanoparticle phase and activity. The electrolyte strongly influenced product selectivity (NaOH led to evolution of CH 4 , Na 2 C 2 O 4 to CO, and KBrO 3 to O 2 ) and induced CuO phase change. A long-term analysis of these processes indicated that during the initial steps, CuO acted as a reactant, rather than as a catalyst, and was converted to CuCO 3 .Cu(OH) 2 , while the as-converted material acted as a catalyst in CO 2 photoreduction, with conversion values comparable to those reported in the literature.