Engineered photocatalytic fuel cell with oxygen vacancies-rich rGO/BiO1−xI as photoanode and biomass-derived N-doped carbon as cathode: Promotion of reactive oxygen species production via Fe2+/Fe3+ redox

A visible-light-driven photocatalytic fuel cell system integrating electro-Fenton process (EF-PFC), comprised of oxygen vacancies-rich rGO/BiO 1−x I photoanode and biomass-derived N-doped carbon (BNC) cathode, was developed to eliminate organic pollutant and generate electricity synchronously. The structure and properties of rGO/BiO 1−x I were characterized by means of XRD, SEM, TEM, solid-state EPR, FTIR, Raman, XPS, UV-vis DRS and PL spectra. The photoelectrochemical activity of rGO/BiO 1−x I was characterized by Mott-Schottky plots, photocurrent responses and EIS. The experimental results indicated that the introduced oxygen vacancies and graphene modification not only promoted the light-harvesting ability but also greatly improved the generation and transfer rate of charge carriers. Most importanly, BNC, acted as cathode, could efficiently reduce oxygen to H 2 O 2 , thus leading to more ·OH production in the presence of Fe 2+ . Simultaneously, the photogenerated electron could efficiently accelerate Fe 2+ /Fe 3+ redox cycling for continuous Fenton reaction and increasing electricity generation in synergistic EF-PFC system. Using formic acid as sacrificial fuel, approximately 68% removal efficiency was reached in rGO/BiO 1−x I-BNC EF-PFC system under visible light irradiation for 240 min while the photocurrent density ( J sc ) and the maximum power density ( P max ) were measured to be 133.18 μA cm −2 and 17.50 μW cm −2 . Furthermore, the radicals trapping   experiments, hydrogen peroxide quantitative studies and ESR tests clearly revealed the mechanism of enhanced performance in rGO/BiO 1−x I-BNC EF-PFC system. Therefore, this engineered rGO/BiO 1−x I-BNC EF-PFC system with the cooperation of Fe 2+ /Fe 3+ redox is a promising means to eliminate organic pollutants and generate electricity synchronously.