Novel composites composed of graphitic carbon nitride (GCN) and p-type semiconductor of NiO nanosheet arrays were fabricated for the first time and demonstrated to be efficient photocathodes for enhancing charge separation and hole transfer. The NiO nanosheet arrays could effectively suppress the charge recombination of the GCN, and photo-generated holes could be effectively transferred to conductive substrates. The photocurrent density could be significantly improved up to −70 μA cm⁻² at 0.42 V versus a reversible hydrogen electrode (RHE) under visible light irradiation, which is nearly 60 times higher than that of pristine GCN under the same conditions. This work would open a new door for the design of highly efficient photocathode materials based on GCN.