ABSTRACT
In this novel research, S-scheme Ag2CrO4/g-C3N4 heterojunctions were generated by sonochemical hybridization of different compositions of Ag2CrO4 nanoparticles [EVB = +2.21 eV] and g-C3N4 sheets [ECB = -1.3 eV] for destructing RhB dye under artificial solar radiation. The as-synthesized nanocomposites were subjected to X-ray diffraction [XRD], diffuse reflectance spectrum [DRS], X-ray photoelectron spectroscopy [XPS], N2-adsorption-desorption isotherm, photoluminescence [PL] and high resolution transmission electron microscope [HRTEM] analysis to explore the interfacial interactions between g-C3N4 sheets and Ag2CrO4 nanoparticles. Spherical Ag2CrO4 nanoparticles deposited homogeneously on the wrinkles points of g-C3N4 sheets at nearly equidistant from each other facilitating the uniform absorption of solar radiations. The absorbability of solar radiations was enhanced by introducing 20 wt % Ag2CrO4 on g-C3N4 sheets. The surface area of g-C3N4 sheets was reduced from 37.5 to 16.4 m2/g and PL signal intensity diminished by 80 % implying the successful interfacial interaction between Ag2CrO4 nanoparticles and g-C3N4 sheets. The photocatalytic performance of heterojunctions containing 20 % Ag2CrO4 and 80 % g-C3N4 destructed 96 % of RhB dye compared with 60 and 33 % removal on the surface of pristine g-C3N4 sheets and Ag2CrO4, respectively. Benzoquinone and ammonium oxalate are strongly scavenged the dye decomposition revealing the strong influence of valence band holes of Ag2CrO4 and superoxide radicals in destructing RhB dye under solar radiations. S-scheme charge transportation mechanism was suggested rather than type II heterojunction on the light of scavenger trapping experiments results and PL spectrum of terephthalic acid. Overall, this research work illustrated the manipulation of novel S-scheme heterojunction with efficient redox power for destructing various organic pollutants persisted in water resources.
ABSTRACT
In this research, S-scheme heterojunctions composed of different concentrations of CuO and ZnO nanoparticles are fabricated for eradicating rhodamine B dye under solar radiation. ZnO nanoparticles are designed through a facile sol-gel route employing Triton X-100. Spherical CuO nanoparticles of 15.2 nm and 1.5 eV band gap energy are deposited on ZnO nanoparticles in an ultrasonic bath of 300 W intensity. The physicochemical performance of the photocatalyst is explored by HRTEM, SAED, BET, XRD, DRS and PL. The in situ homogeneous growth of spherical CuO nanoparticles on ZnO active centers shifts the photocatalytic response to the deep visible region and enhances the efficiency of charge carrier separation and transportation. Among all heterojunctions, ZnCu10 containing 10 wt% CuO displays the best photocatalytic rate for expelling 93% of RhB dye within 240 min, which is twenty-fold higher than that of pristine ZnO and CuO. Reactive oxygen species are the predominant species in degrading the dye pollutant on the heterojunction surface, as shown from scrubber trapping experiments and PL spectrum of terephthalic acid. Coupling ZnO as an oxidative photocatalyst and CuO as a reductive photocatalyst generates an efficient S-scheme heterojunction with strong redox power in destructing various organic pollutants.
