Dual electrochemical catalysis of Bi2Mo3O12/Ti cathode for hydrogen peroxide production in electro-Fenton system

Abstract

In electro-Fenton (EF) technique, the yield of H2O2 is one of important factors affecting the wastewater treatment efficiency, which greatly depends on the cathode material. Recently the metal oxide modified cathode has become one of the most efficient materials for oxygen reduction and H2O2 production. In this paper, a bismuth molybdate with distorted scheelite structure, Bi2Mo3O12, was synthesized and used as cathode to catalyze H2O2 production. The prepared Bi2Mo3O12 was characterized by SEM, FTIR and XPS. The study on voltammetric behavior of Bi2(MoO4)3/Ti cathode found that Bi2Mo3O12 had a dual electrochemical catalysis for H2O2 production, and that was further verified by the high yield of H2O2 for short time in bulk electrolysis. The dual electrochemical catalysis includes a direct electrochemical catalysis and an indirect Bi0 mediated chemical catalysis. Production of chemisorbed oxygen, which is caused by the oxygen vacancies originated from both the distorted scheelite lattice and the electro-generated lower-valence Bi specie at lattice surface, contributes to the direct catalysis. Otherwise, the electro-generated Bi0 from Bi3+ reduction reacts with adsorbed oxygen to H2O2, enhancing H2O2 production. Additionally, Bi2Mo3O12/Ti was used as cathode in EF system containing ferric alginate gel beads. This EF system shows high efficient characteristics toward the degradation of acid orange II (AOII), and the removal percentage of AOII maintained about 94% in the wide pH range of 3.0–9.0. In brief, this paper not only provides a high efficient Bi2(MoO4)3/Ti cathode for H2O2 production, but also reveals a dual catalysis mechanism using Bi2(MoO4)3 modified cathode in EF system.