Barium Hydrogen Phosphate Electrodes for High Electrocatalytic and Photoelectrocatalytic Degradation of Rhodamine B in Neutral Medium: Optimization by Response Surface Methodology

Abstract

Barium hydrogen phosphate (BaHPO4) thin films were electrodeposited on fluorine-doped tin oxide (FTO) and used as electrocatalysts for organics degradation. The effects of applied current density and deposition time on the phase and morphology of electrodeposited films were analyzed with X-ray diffraction (XRD), scanning electron microscopy (SEM), attenuated total reflectance-Fourier-transform infrared (ATR-FTIR) spectroscopy, Raman spectroscopy, electrochemical impedance spectroscopy (Mott–Schottky) plots, and photocurrent response. The electrodeposited BaHPO4 films crystallize in the orthorhombic structure and form platelets on the FTO substrate. Response surface methodology (RSM) was used to optimize the operational conditions. Four independent process variables were considered: NaCl concentration, rhodamine B (RhB) initial concentration, applied current density, and reaction time. Based on the model prediction, the optimum conditions for RhB degradation were determined with the maximum RhB degradation of 98.78%. The corresponding experimental value of RhB degradation under the optimum conditions was determined as 99%, which is very close to the optimized one, implying that RSM is a powerful strategy for the process optimization. The photoelectrochemical degradation of RhB, performed at optimal operational conditions, allowed the very fast degradation rates of almost 99% during 7 min due to the synergic effect while combining photocatalysis and electrocatalysis.