We studied and compared the photocatalytic water splitting performances for ZnGa2O4 prepared by high temperature solid state reaction (HTSSR), hydrothermal (HY) and sol-gel (SG) methods. HTSSR-ZnGa2O4 has a relative large photocatalytic activity per surface area (1.6 p,mu mol/h/m(2)) in pure water by UV irradiation due to its high crystallinity. The HY- and SG-samples both have small particle sizes (20 similar to 30 nm) and therefore high surface area (20 and 29 m(2)/g, respectively), which leads to superior photocatalytic H-2 evolution rates per unit mass (11.5 and 28.5 mu mol/h/g). The apparent quantum yield of SG-ZnGa2O4 for pure water splitting under 313 nm irradiation is 2.6%. The existence of substantial surface defects is the major problem for HY- and SG-ZnGa2O4. Consequently, the usage of sacrificial agents could greatly enhance the activities and indeed the H-2 evolution rates in 20 Vol. % methanol aqueous solution increase to 100 and 142 mu mol/h/g for HY- and SG-ZnGa2O4, respectively. (C) 2014 Elsevier Ltd. All rights reserved.