“…Several processes have been developed to form TiO 2 photo-anode, such as doctor blade [1,2] , screen printing [3,4] , sputtering [5][6][7] , sol-gel [8,9] , hydrothermal [10][11][12] , spin-coating [13,14] , AP plasma jet [15][16][17] , spray pyrolysis [18,19] and so on. Hydrothermal process possesses low-cost, large-area and easyoperation priorities, was used to synthesize TiO 2 films in many research teams.…”