In this work, we report g-C3N4/rGO/ZnS composites used in photocathodic protection to effectively enhance proton reduction capacity. The g-C3N4/rGO/ZnS composites are synthesized by two-step hydrothermal method. The structure, morphology, and optical properties of the obtained composites are characterized by XRD, SEM, TEM and UV–vis. The performance of photocathodic protection for the 304 stainless steel is evaluated by the photoelectrochemical measurements. Results indicate that ternary composite exhibit enhanced photocathodic protection performance for 304 stainless steel compared with the pure g-C3N4. Especially when the 304 stainless steel is coupled to the 15%-rGO/g-C3N4/ZnS composites, its photo-induced current density at the bias of 0.23 V (vs. SCE) reaches 2180 μA/cm2 which is about 4 times higher than that of g-C3N4 alone. The enhanced photocathodic protection performance is attributed to the high charge carrier separation efficiency. Meanwhile, rGO adjusts the fermi level of 15%-rGO/g-C3N4/ZnS composites which results obviously negative shift of EFB.
