1. College of Chemical Engineering, Hebei Key Laboratory for Environment Photocatalytic and Electrocatalytic Materials, North China University of Science and Technology, No. 21 Bohai Road, Caofeidian new-city, Tangshan, Hebei, 063210, P. R. China
2. Department of Physics and CICECO-Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal