Systematic investigation for the photocatalytic applications of carbon nitride/porous zeolite heterojunction

Abstract

Here, we present the integration of a commercially available titanosilicate zeolite with photocatalyst graphitic carbon nitride (g-C3N4) toward the development of an effective heterojunction photocatalyst, TCN(1-8-8). The formation of this porous heterojunction and its structural details have been confirmed by X-ray diffraction, N2 adsorption, electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The visible light absorption and band structure have been determined from diffused reflectance ultraviolet−visible spectroscopy. For its fabrication, the contents of both the constituent materials have been optimized systematically. Its photocatalytic activity has been found to be impressive in the visible light-assisted degradation of a variety of water pollutants (dyes and antibiotics) and in the hydroxylation of phenol. Control experiments, radical scavenging/trapping experiments, influence of the reaction environment, and photoelectrochemical measurements have been carried out to establish the structure−activity relationship and the plausible reaction mechanisms. The various fragmented products, formed during the degradation of parent molecules, have been further confirmed using electrospray ionization mass spectrometry analysis. The photocatalytic degradation of 98, 96, 95, and 92%; rate constants of 0.0125, 0.01244, 0.0058, and 0.0040 min−1; and reduction of total organic concentrations of 63, 59, 57, and 55% for rhodamine B, sulforhodamine B, tetracycline, and ciprofloxacin have been achieved in 6 h, respectively. The activity of TCN(1-8-8) has been observed to be better than the state-of-the-art photocatalyst TiO2 (Degussa P25). Besides, it has also exhibited excellent degradation activity in natural solar light. The effective adsorption of pollutant molecules over the active surface, efficient charge separation at the interface, migration and retardation of charge carriers recombination process, and tailored charge-carrier dynamics in the excited state have all been identified as reasons for the higher activity. This study, therefore, provides a comprehensive and systematic grasp on the development of an economical catalyst for photocatalytic hydroxylation reaction and wastewater treatment.