Photocatalytic performance of ZnGa2O4 for degradation of methylene blue and its improvement by doping with Cd

ZnGa2O4 powder catalysts, synthesized by a sol–gel process, exhibit high photocatalytic activity for methylene blue (MB) degradation. The pH value at the point of zero charge (pHpzc) was determined to be 5.9 by a titrations method and MB conversion increased with the increase of the pH value. The valence and conduction band positions were determined at 3.35 V and − 1.45 V (Normal Hydrogen Electrode, NHE), respectively, indicating high photocatalytic ability. Improved photocatalytic efficiency was achieved by substituting cadmium for zinc in the ZnGa2O4. The improvement can be attributed to high UV absorption efficiency and high separation of photogenerated electron-hole pairs.