One-step synthesis of MnOx/g-C3N4 nanocomposites for enhancing the visible light photoelectrochemical oxidation performance

[Display omitted] •MnOx enhances the separation rate of photogenerated carriers.•Photoelectrochemical (PEC) degradation of clofibric acid (CA) is investigated.•MnOx/g-C3N4 photoanode shows high performance for PEC degradation of CA.•Valence state transitions of Mn are analyzed by electrochemical characterization.•Superoxide radical and positive holes play dominant roles in PEC degradation of CA. Here, we report enhancement of the photoelectrochemical (PEC) performance of MnOx/graphite-like carbon nitride (g-C3N4) nanocomposites synthesized by one-step thermal decomposition for degradation of clofibric acid (CA). MnOx showed enhanced broadband ultraviolet–visible light regions, efficient charge generation–separation, and enhanced PEC performance when combined with g-C3N4. Photogenerated holes can be efficiently captured by introducing Mn2+/Mn3+/Mn4+ valence band transitions. In addition to a good visible-light response, the MnOx/g-C3N4-10 (g-C3N4 with 10% Mn(NO3)2·6H2O) photoanode showed enhanced photocurrent density of 0.03 × 10−3 A cm−2 at 0.63 V vs. Ag/AgCl, which was approximately 100 times that of pristine g-C3N4. The superoxide radical and positive holes played dominant roles in PEC degradation of CA. The MnOx/g-C3N4-10 photoanode showed the highest photoelectrocatalytic performance under acidic conditions because of electrostatic attraction between the electrode and CA. The CA degradation ratio using the MnOx/g-C3N4-10 photoanode was 100% under visible light in 6 h at pH = 3. This work provides a simple and sustainable strategy to modify g-C3N4 for captured holes to improve PEC degradation of CA, and it is promising for application to different materials in a variety of fields.