Sonochemical synthesis of Ag<inf>2</inf>CO<inf>3</inf>/CeO<inf>2</inf> p-n heterojunction for decomposition of rhodamine B dye

Abstract

Given their strong resistance to degradation and potential risks to both human health and aquatic life, the proper treatment of organic pollutants disposed in wastewater has received a lot of attention. In this study, we describe the development of an effective Ag2CO3/CeO2 p-n junction for the photocatalytic reduction of rhodamine B dye as a model cationic pollutant under UV radiation. Ag2CO3/CeO2 heterojunction was formed by combining sol-gel and sonochemical routes, on which silver carbonate is successfully distributed in a uniform arrangement on localized active sites in an ultrasonic bath of 300 W intensity. The physicochemical features of the solid specimen were explored via XRD, HRTEM, DRS, and PL experimental analysis. Ag2CO3 depresses the band gap energy of CeO2 revealing the shifting in the photocatalytic response to the visible region. The removal of RhB dye was performed under UV light radiation; however, the amount removed by the adsorption process does not exceed 15%. The decomposition of rhodamine B dye was carried out at a rate of 0.0035 min−1 for the optimum sample containing 5 wt % Ag2CO3 which is sevenfold higher than that on the surface of pristine CeO2 nanoparticles. The charge carrier migration proceeds through the type (II) heterojunction route by electron transfer from the conduction band of CeO2 to that of Ag2CO3.On the other hand, the positive hole jumps from the valence band of Ag2CO3 to that of CeO2. The charge carrier transportation occurs at the interface of the heterojunction until the Fermi levels of both oxidative and reductive are equilibrated and produce a strong inner electric field. The oxidation properties are determined by the positive holes of CeO2, while the reduced properties are controlled by the conduction band electrons of silver carbonate. The novel p–n junction is considered an excellent heterojunction for many photocatalytic applications.