Enhanced O₂⁻[rad] and HO[rad] via in situ generating H₂O₂ at activated graphite felt cathode for efficient photocatalytic fuel cell

The use of a photocatalytic fuel cell (PFC) in wastewater treatment is an intensively researched topic because the device integrates organic pollutant degradation and chemical energy recovery. Herein, we proposed a strategy to enhance PFC performance by increasing the concentrations of hydroxyl radical (HO[rad]) and superoxide radical (O₂⁻[rad]) produced from H₂O₂ generated in situ using an activated graphite felt (GF) cathode. This cathode was prepared by H₂SO₄ treatment to introduce oxygen-containing functional groups on its surface that would serve as surface-active sites and facilitate the two-electron pathway of H₂O₂ production. Remarkably, the peak current density of the activated GF cathode (−1.25 mA/cm²) was more than thrice that of the original GF cathode (−0.40 mA/cm²), and its Faradaic efficiency significantly improved from 20.01% to 74.09%. The PFC equipped with the activated GF cathode harvested 2.69 times the maximum power density (JV_max) and 5.15 times the degradation rate of the traditional Pt black-PFC system. This was because the O₂[rad]⁻ and HO[rad] concentrations, respectively, were 2.87 (23.98 × 10⁻⁵ M) and 2.48 times (13.00 × 10⁻⁴ M) as high as those in the Pt black-PFC system. These results were attributed to the high concentration of H₂O₂ generated in situ at the activated GF cathode, which was 25.13 times (0.402 mM) as high as that generated at the Pt black cathode. Thus, the proposed PFC system demonstrates the feasibility of improving organic pollutant degradation and energy recovery by enhancing H₂O₂ production.