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/BiO1-xI 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/BiO1-xI 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/BiO1-xI 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 H2O2, thus leading to more center dot OH production in the presence of Fe2+. Simultaneously, the photogenerated electron could efficiently accelerate Fe2+/Fe3+ 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/BiO1-xI-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 mu A cm(-2) and 17.50 mu W cm(-2). Furthermore, the radicals trapping experiments, hydrogen peroxide quantitative studies and ESR tests clearly revealed the mechanism of enhanced performance in rGO/BiO1-xI-BNC EF-PFC system. Therefore, this engineered rGO/BiO1-xI-BNC EF-PFC system with the cooperation of Fe2+/Fe3+ redox is a promising means to eliminate organic pollutants and generate electricity synchronously.