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

Abstract

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 Mo0.3Fe1Co3–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, Mo0.3Fe1Co3–Se MAs exhibits superior oxygen evolution reaction (OER) property, with an overpotential of only 235 mV (10 mA/cm2). Compared with Fe1Co3 MAs or Mo0.3Fe1Co3 MAs, density functional theory (DFT) demonstrated that the better catalytic capacity of Mo0.3Fe1Co3–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 Mo0.3Fe1Co3–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.