Construction of heterojunction photoanode via facile synthesis of CoOx/CN nanocomposites for enhanced visible-light-driven photoelectrochemical degradation of clofibric acid.

Abstract Visible-light-driven photoelectrocatalytic (PEC) oxidation has been explored extensively to develop highly active materials. Herein, a visible-light-active p-Co3O4 and n-g-C3N4 heterojunction (CoOx/CN) photoanode, constructed by simple one-pot calcination, was shown to remove clofibric acid (CA) from water through a PEC process. Compared with pristine g-C3N4, the optimal photoanode (15%-CoOx/CN) exhibited stable and effective PEC performance and CA degradation performance, a 100-fold enhancement in photocurrent density, and around 1.5-fold decreased efficiency over 6 h. The p–n heterojunctions were shown to increased the charge density and conductivity of g-C3N4 for rapid charge transfer. Furthermore, interface contact broadened the visible light absorption and accelerated charge carrier transfer. Notably, the catalysts established p–n heterojunctions, which hindered the bulk recombination of photoinduced carriers and improved the charge separation efficiency. The CoOx/CN photoanodes showed a pair of redox peaks at a potential of 0.3 V vs. Ag/AgCl, indicating good Co3O4 redox behavior under alkaline conditions. The 15%-CoOx/CN photoanode displayed excellent PEC performance of up to 0.16 mA cm−2 in 0.1 M KOH solution at 1.23 V vs. RHE (reversible hydrogen electrode) and long-term stability for up to 12 h. The CoOx/CN photoanodes maintained excellent PEC activities for CA removal, even under acidic and alkaline conditions conditions (pH 3–10). Probable degradation pathway of CA was proposed according to the main degradation intermediates. This study shows that the synergistic effect of p–n heterojunctions in photoelectrodes provides a new approach to the rational application of new photoanode candidates and PEC performance optimization.