Bifunctional Mo-doped FeCo–Se aerogels catalysts with excellent OER and ORR activities for electro-Fenton process

Antibiotic pollution in aqueous solutions seriously endangers the natural environment and public health. In this work, Mo-doped transition metal FeCo–Se metal aerogels (MAs) were investigated as bifunctional catalysts for the removal of sulfamethazine (SMT) in solution. The optimal Mo_0.3Fe₁Co₃–Se catalyst can remove 97.7% of SMT within 60 min (SMT content: 10 mg/L, current intensity: 10 mA/cm²). The unique porous cross-linked structure of aerogel confered the catalyst sufficient active sites and efficient mass transfer channels. For the anode, Mo_0.3Fe₁Co₃–Se MAs exhibits superior oxygen evolution reaction (OER) property, with an overpotential of only 235 mV (10 mA/cm²). Compared with Fe₁Co₃ MAs or Mo_0.3Fe₁Co₃ MAs, density functional theory (DFT) demonstrated that the better catalytic capacity of Mo_0.3Fe₁Co₃–Se MAs is attributed to the doping of Mo species and selenization lowers the energy barrier for the ∗OOH to O₂ step in the OER process. Excellent OER performance ensures the self-oxygenation in this system, avoiding the addition of air or oxygen in the traditional electro-Fenton process. For the cathode, Mo doping can lead to the lattice contraction and metallic character of CoSe₂, which is beneficial to accelerate electron transfer. The adjacent Co active sites effectively adsorb ∗OOH and inhibit the breakage of the O–O bond. Rotating ring disk electrode (RRDE) test indicated that Mo_0.3Fe₁Co₃–Se MAs has an excellent 2e⁻ ORR activity with H₂O₂ selectivity up to 88%, and the generated H₂O₂ is activated by the adjacent Fe site through heterogeneous Fenton process to generate ·OH.