Development of Na2Ti6O13/CuO/Cu2O heterostructures for solar photocatalytic production of low-carbon fuels

Abstract Na2Ti6O13/CuO/Cu2O materials were prepared by solid-state and impregnation method, using copper oxide as cocatalyst (CC, 0.1%–5%). The catalytic activity was evaluated for H2 evolution and CO2 reduction. XPS analysis revealed the presence of Cu2O and CuO in different proportions. Na2Ti6O13 impregnated with 0.1% of cocatalyst exhibits majoritary the Cu2O phase; while Na2Ti6O13 with 5% of cocatalyst shows mainly CuO. Electrochemical measurements showed higher photocurrent and lower resistance to charge transference in Na2Ti6O13-0.1% CC, associated with better a charge flow. Na2Ti6O13-0.1% CC exhibited the highest H2 production (33 μmol g-1 h-1) and Na2Ti6O13-5% CC showed the best CO2 conversion to CH2O (25 μmol g-1 h-1) and CH3OH (4.6 μmol g-1 h-1). A major content of Cu2O phase favored the H2 evolution by the formation of a Z-scheme, where the strong negative character of the CB of Cu2O enhances the kinetics of H2O reduction, while a higher content of CuO improved CO2 adsorption and reduction.