Radical reaction-wastewater fuel cell with Fe-modified graphene hydrogel particle electrodes

The treatment of organic wastewater and simultaneous energy recovery with photocatalytic fuel cells (PFCs) is important but limited by the low oxidation efficiency of organic degradation. Herein, we propose a radical reaction-wastewater fuel cell (RR-WFC) system by introducing the Fe modified graphene hydrogels (Fe/GHs) as particle electrodes into a conventional PFC. Under an electric field, the Fe/GHs were polarized to form numerous microelectrodes with cathodic and anodic potentials, which facilitated electron/mass transfer and drove a remarkable 28-fold increase in O₂•^- concentration. The Fe³⁺/Fe²⁺ redox cycling on the surfaces of the Fe/GHs was significantly strengthened due to the rapid in situ reduction of the embedded Fe³⁺ to Fe²⁺ by O₂•^-, which contributed to a considerable increase in the steady-state HO• concentration by 379 % and consequently an exceptional improvement in both organic degradation and electricity generation. The rate constant and the maximum output power density for the typical dye (Rhodamine B, RhB) degradation were increased by 227 % and 215 %, respectively, in the RR-WFC system. This work presents a novel and sustainable strategy for the highly efficient resource treatment of organic wastewater.