Stable and selective electrosynthesis of hydrogen peroxide and the electro-Fenton process on CoSe2 polymorph catalysts

Abstract

Electrochemical synthesis of hydrogen peroxide (H₂O₂) in acidic solution can enable the electro-Fenton process for decentralized environmental remediation, but robust and inexpensive electrocatalysts for the selective two-electron oxygen reduction reaction (2e⁻ ORR) are lacking. Here, we present a joint computational/experimental study that shows both structural polymorphs of earth-abundant cobalt diselenide (orthorhombic o-CoSe₂ and cubic c-CoSe₂) are stable against surface oxidation and catalyst leaching due to the weak O* binding to Se sites, are highly active and selective for the 2e⁻ ORR, and deliver higher kinetic current densities for H₂O₂ production than the state-of-the-art noble metal or single-atom catalysts in acidic solution. o-CoSe₂ nanowires directly grown on carbon paper electrodes allow for the steady bulk electrosynthesis of H₂O₂ in 0.05 M H₂SO₄ with a practically useful accumulated concentration of 547 ppm, the highest among the reported 2e⁻ ORR catalysts in acidic solution. Such efficient and stable H₂O₂ electrogeneration further enables the effective electro-Fenton process for model organic pollutant degradation.