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

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 H 2 production of TiO 2 by co-loading of oxidation cocatalyst Co 3 O 4 with reduction cocatalyst CuO , wherein the Co 3 O 4 loading amount was significant especially for TiO 2 loaded with sufficient or optimum CuO. In comparison with that on TiO 2 loaded with only CuO, the photocatalytic H 2 production from water over TiO 2 photocatalyst co-loaded with CuO and trace Co 3 O 4 was enhanced by approximately 5.5 times, even though complex spatial control was not adopted. In contrast, remarkable improvement of photocatalytic activity after Co 3 O 4 co-loading was only observed on TiO 2 photocatalysts loaded with less CuO in the presence of methanol. Better separation of photogenerated charges on the surface of dual-cocatalysts modified TiO 2 was further demonstrated by decreased luminescence as well as increased photogenerated electrons and hydroxyl radicals as compared to those loaded with only CuO.