TiO2/CuO photoelectrocatalysts as enhanced photoanodes for oxygen evolution reaction

• Cu modified TiO 2 photoelectrocatalysts can be synthesized using supercritical media. • Combined TiO 2 CuO materials with higher Cu concentration show lower band gap energy. • Intermediate Cu concentration (from 3 to 13 %) lead to good catalytic activity in OER. • TiO 2 /Cu 6.5 % catalyst exhibited the highest activity improvement under illumination. • TiO 2 /Cu 6.5 % photoelectroanode performs outstanding OER activity. This work addresses the synthesis of effective photoelectrocatalysts to be used as anodic material for the oxygen evolution reaction (OER) consisting of TiO 2 modified with Cu oxides by one pot supercritical fluid synthesis at Cu concentrations from 3 to 13 %. The catalysts obtained involve TiO 2 anatase phase nanoparticles combined with Cu oxides (mainly CuO). The combined TiO 2 /Cu materials with higher Cu concentration show lower band gap energies. Better charge transfer capability has been observed in TiO 2 /Cu catalysts with intermediate Cu concentrations (6.5 and 8 %) in the absence of light. LSV have been used to test the activity of these catalysts in OER. TiO 2 /Cu 6.5 % catalyst have exhibited the highest activity towards OER, as well as the highest improvement under simulated sunlight illumination. This may be attributed to an adequate combination in TiO 2 /Cu 6.5 % of low band gap energy and low charge transfer resistance, that seem to promote the synergy of the electro- and photocatalytic roles of the catalyst to favour the oxidation of water to oxygen. Similar or even better OER activity has been attained with this anodic material compared to that reported in several works in the literature with more complex anodes.