Enhancing photocatalytic H2 evolution from water on CuO-Co3O4/TiO2: The key roles of Co3O4 loading amounts

Abstract

Spatially controlled co-loading of both oxidation and reduction cocatalysts on semiconductor photocatalysts has been demonstrated to be favorable for photogenerated charge separation and thus enhanced photocatalytic activity. Herein, we presented a simple ball-milling method to improve photocatalytic H2 production of TiO2 by co-loading of oxidation cocatalyst Co3O4 with reduction cocatalyst CuO, wherein the Co3O4 loading amount was significant especially for TiO2 loaded with sufficient or optimum CuO. In comparison with that on TiO2 loaded with only CuO, the photocatalytic H2 production from water over TiO2 photocatalyst co-loaded with CuO and trace Co3O4 was enhanced by approximately 5.5 times, even though complex spatial control was not adopted. In contrast, remarkable improvement of photocatalytic activity after Co3O4 co-loading was only observed on TiO2 photocatalysts loaded with less CuO in the presence of methanol. Better separation of photogenerated charges on the surface of dual-cocatalysts modified TiO2 was further demonstrated by decreased luminescence as well as increased photogenerated electrons and hydroxyl radicals as compared to those loaded with only CuO.