Flexible and free-standing polyvinyl alcohol-reduced graphene oxide-Cu2O/CuO thin films for electrochemical reduction of carbon dioxide

Flexible and free-standing thin films were fabricated and employed directly as working electrodes for the electrochemical reduction of CO2 in 0.5 N KHCO3 at 25 degrees C, in which, various sizes of Cu2O nanocubes (similar to 27 +/- 2, 37 +/- 3, 62 +/- 4 and 207 +/- 3 nm) with different extent of surface oxidation (13, 20, 66, and 64% of Cu(II)) were reinforced on to polyvinyl alcohol/reduced graphene oxide matrix (PVA/rGO/(Cu2O/CuO_X, where, X =without halide, Cl, Br and I). The size of Cu2O nanocubes and their surface oxidation were systematically altered by the addition of 1 mL of 10 mM sodium halides (NaCl, NaBr, and NaI) during the synthesis. Energy-dispersive X-ray spectroscopy mapping displayed the specific adsorption of Cl- ions over the Cu2O surface, whereas Br- and I- ions did not show such behaviour. PVA/rGO/(Cu2O/CuO_Cl) thin film exhibited a low overpotential of 20 mV for CO2 reduction reaction and, similar to 60 and similar to 7 times higher current density at - 0.80 V vs. RHE compared to that of the PVA/rGO/(Cu2O/CuO), PVA/rGO/(Cu2O/CuO_Br) approximate to PVA/rGO/(Cu2O/CuO_I), respectively. Gas chromatography and H-1-NMR analyses confirmed methanol as the single liquid product, with a faradaic efficiency of 63% at - 0.75 V vs. RHE on PVA/rGO/(Cu2O/CuO_Cl) thin film. [GRAPHICS] .