Hierarchical Iron Phosphides Composite Confined in Ultrathin Carbon Layer as Effective Heterogeneous Electro‐Fenton Catalyst with Prominent Stability and Catalytic Activity

Abstract The heterogeneous electro‐Fenton (EF) process is a promising wastewater treatment technology for the onsite production of H₂O₂ and avoidance of iron sludge. However, the preparation of the cathode catalysts remains a challenge. Not only must the catalyst surface possesses active sites for both 2e⁻ oxygen reduction reaction and heterogeneous Fenton reaction, preventing active metals from continuous leaching is also crucial to maintain its catalytic activity. Herein, a heterogeneous catalyst (rGO@Fe_xP/C) with a vacuumized package‐like structure, where carbon‐supported iron phosphides (Fe_xP/C) are tightly covered within interconnected reduced graphene oxide (rGO) sheets, is successfully prepared. The concentration of iron that dissolved from rGO@Fe_xP/C after the reaction is only 3.37% of bare Fe_xP/C (14.6 mg L⁻¹), while rGO@Fe_xP/C achieves better performance towards sulfamethoxazole (10 mg L⁻¹) degradation than Fe_xP/C. Investigation on rGO@Fe_xP/C with different thicknesses of outer rGO layer and diverse morphologic structures demonstrate that the unique structure of rGO@Fe_xP/C played a decisive role in the simultaneously enhanced activity and stability.