Mechanism of UV Driven Photoelectrocatalytic Degradation Berberine Chloride Form Using the ESR Spin-trapping Method

Abstract

Photoelectrocatalytic (PEC) system greatly improves the migration of photo-excited charges, retards the fast recombination of electron–hole and increases the lifetime of photo-generated holes. In this paper, we constructed a novel PEC system to degrade Berberine chloride form (BCF). XRD patterns indicated ageing time was an important condition for the crystal type of TiO₂ and the best proportion of anatase/rutile was 80/20. The band gap energy of the TiO₂ was 3.01 eV. We demonstrated that a synergistic effect existed between photocatalysis (PC) and electrocatalysis (EC). Besides we discussed the influence of pH, current density, the amount of catalyst and initial BCF concentration on the degradation of BCF. Electron spin resonance (ESR) through spin trap 5, 5-dimethyl-1-pyrroline-N-oxide (DMPO) and the scavenging experiments suggested that the reactive oxygen species (ROS) were superoxide radicals (O₂^•−), hydroxyl radicals (·OH) and sulfate radical (SO₄^•−) in PEC system. Furthermore, we compared the two pathway of formation DMPO-SO₄ adducts, and found that SO₄^·- was the most major oxidized species in degrading BCF. We proposed a plausible reaction mechanism. Intriguingly, even under lower current and weaker light conditions, the PEC process maintained its effectiveness, demonstrating the feasibility of the PEC approach.

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