MoSe₂ nanoflakes decorated ZnO nanorods: An effective photoelectrode with S-scheme heterojunction for photoelectrocatalytic degradation of tetracycline and rhodamine B

Photoelectrocatalysis has been extensively used as one of the most widely known advanced oxidation processes (AOPs) owing to its superiority over photocatalytic systems with regards to the reduced recombination of charge carriers. ZnO demonstrates profound performance in PEC systems, and to overcome the obstacle of its limited visible light utilization, heterojunction formation of transition metal dichalcogenides (TMDs) with this classical semiconductor is proposed. Herein, MoSe₂ was introduced onto ZnO nanorods to widen its visible light absorption and consequently boost the PEC ability of the proposed composite in omitting model organic contaminants in water. The as-synthesized nanocomposite was immobilized onto FTO by Electrophoretic deposition (EPD) technique which is then represented as the working electrode in the three-electrode PEC system. The characterization of the proposed nanocomposite was attained by techniques including: XRD, FESEM, FTIR, DRS and EDX. Moreover, electrochemical characterization was conducted to study its electrochemical properties. The PEC activity of the samples was studied by the degradation of Rhodamine B dye (62.3%) and tetracycline pharmaceutical (70.2%) under irradiation. The results indicated a much higher PEC ability for ZnO NR/MoSe₂/FTO photoelectrode than its bare parent samples as well as its recyclability. To study the impact of the operational parameters, the electrolyte's concentration, initial pH, external bias voltage and initial concentration of the contaminant were investigated. By means of the scavenging tests, electrons and holes have the highest and the lowest importance in the PEC reaction, respectively. The S-scheme mechanism of degradation was proposed based on the cumulative experimental data.