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.