P-type CuBi2O4 represents a very promising photocathode material with visible light response for dual absorber photoelectrochemical (PEC) water splitting device. However, its photocurrent reported is limited by its inefficient utilization of photogenerated carriers, which greatly hinders its practical application. Herein, CuBi2O4 films were prepared by a simple spin-coating method and four distinct ramping rates were applied to investigate the influence of annealing rate on its hydrogen production activity. Among four different ramping rates, the CuBi2O4 film annealed with the rate of 2 degrees C/min successfully achieved the highest photocurrent of 0.68 mA/cm(2) at 0.25 V-RHE, corresponding to 38%-83% improvement when compared to those prepared with other rates. To reveal the working mechanism of this simple but effective heating control, structural and electrochemical characterizations were performed. It was found that, the electronic structure of the best performing CuBi2O4 film was notably modified with the largest amount of low valence Cu+ species. Meanwhile, the highest carrier concentration was measured through electrode impedance investigation. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.