Cobalt-enhanced CoxFe3-xO4 photoanode for ultrafast photoelectrodegradation of organic dyes with an integrated RSM optimization

Abstract

In this work, two compositions of cobalt ferrite (CoxFe3-xO4: x=1 and 1.5) were investigated as photoanodes for the photoelectrocatalytic (PEC) degradation of Rhodamine B. The structural and textural investigations confirmed the cubic spinel structure with monocrystalline grain size around 8 nm and high surface area (>100 m2/g). The bandgap values of the samples, 2.32 eV (for x=1) and 2.18 eV (for x=1.5), enable visible light absorption and activation under sunlight. The catalytic results showed that complete degradation with a complete mineralization of rhodamine B was obtained. The RSM optimization studies allowed to identify the optimum degradation (100%) conditions in terms of Na2SO4 concentration, current density, initial RhB concentration and reaction time. The chemical trapping tests and redox potential study have confirmed that OH• and h+ are the primary species driving the degradation process. Advanced characterizations were carried out to investigate the electrocatalytic and photo electrochemical properties. A high cobalt content improves the lifetime and charge carriers transfer and higher photogenerated electron-hole, confirming an enhancement in the photocatalytic potential. Photons with wavelengths corresponding to an energy higher than that of the bandgap allowed an efficient degradation (100% in 6 minutes). Furthermore, a comparative investigation of photocatalytic, electrocatalytic, and photo-electrocatalytic processes revealed a pronounced synergistic effect in the combined PEC system using CoxFe3-xO4 spinel as photoanode.