Interface optimization by impedance spectroscopy and photoelectrocatalytic degradation of clofibric acid

Highlights: • A simple and fast way to optimize the optimum degradation conditions by impedance spectroscopy. • The FeOOH/P:BiVO₄/rGO exhibits much improved photoelectrochemical activity. • The photoanode efficient removal efficiencies for clofibric acid. • A plausible PEC degradation clofibric acid mechanism was proposed. -- Abstract: Clofibric acid (CA) is a ubiquitous pollutant that is resistant to traditional wastewater treatments. Here, photoelectrocatalytic (PEC) degradation of CA using a FeOOH/P:BiVO₄/rGO photoanode is investigated. The characteristics by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) on the electrode-electrolyte interface were performed to optimize different electrolyte conditions (Na₂SO₄ concentration, CA concentration, and pH). EIS is found to be a simple, fast method to study the electrolyte conditions for PEC decomposition of CA on BiVO₄ composites electrodes. The experimental results demonstrated that the electrolyte conditions had an effect on the surface coverage of V⁵⁺/V⁴⁺ redox species and surface states related to ion/molecule distribution on the electrode surface. The optimum deposition time was 6 min. And the optimum electrolyte conditions were as follows: the concentration of Na₂SO₄ was 0.2 mol L⁻¹, the concentration of clofibric acid was 5 mg L⁻¹, and pH was 7. Under these conditions, FeOOH/P:BiVO₄/rGO photoanode showed a removal rate of CA 96% in 6 h under visible light irradiation (λ ≥ 420 nm). It also showed a good photoelectric stability. FeOOH/P:BiVO₄/rGO photoanode showed a potential application in the photoelectrochemical degradation of CA.