CO2-activated graphite felt as an effective substrate to promote hydrogen peroxide synthesis and enhance the electro-Fenton activity of graphite/ Fe3O4 composites in situ fabricated from acid mine drainage

Activating graphite electrodes to improve the selectivity of a 2-electron oxygen reduction reaction (ORR) and enhance heterogeneous Fenton catalyst loading is an effective method for restoring the water environment. Herein, the structures and properties of CO2-activated graphite felt (GF-CO2), which achieves effective etching at high temperatures in CO2 atmosphere, are evaluated. Oxygen-containing functional groups and defects are formed on the surface of GF-CO2, which improved the electrochemical behavior of GF, producing 2.86 times greater H2O2 accumulation in an hour than GF-Raw. Using GFs as the anode in air-cathode fuel cells, GF@Fe3O4 composites are fabricated in situ from acid mine drainage (AMD). The application of GF-CO2@Fe3O4 as an electro-Fenton (E-Fenton) cathode exhibited efficient removal (98.8 %) and mineralizing (80.4 %) of chloroquine (CLQ) in 40 min and 240 min, respectively. Since it is favorable to enhance Fenton oxidation activities, the efficiency enhancement is attributed to the higher H2O2 electrogeneration efficiency and metal content of the prepared GF-CO2@Fe3O4 composite. The heterogeneous E-Fenton systems equipped with the GF-CO2@Fe3O4 composite can be operated in a wide pH range and eliminate various organic pollutants. Thus, CO2 activation of GF is a promising strategy to improve the efficiency of heterogeneous E-Fenton catalyst of GF@Fe3O4 cathodes fabricated from AMD. This technology provides an environmentally friendly approach to restoring accessibility to fresh, clean water in an era where water scarcity threatens the water supply.