Synthesis of carbon quantum dots decorated titanium disilicide: a novel hybrid solar-driven photocatalyst for sustainable wastewater treatment

Abstract

Producing an efficient solar driven semiconductor photocatalyst is required for harnessing the maximum amount of solar light for sustainable application in solving real-world problems. In the present work, a novel nanohybrid titanium disilicide/carbon quantum dot (TiSi₂/CQD)-based composite photocatalyst was prepared via sonication followed by one-pot hydrothermal treatment. Several spectroscopic and microscopic techniques were used to investigate the successful composite formation with the detection of new electrostatic interactions and an overall increase in crystallinity and optoelectronic as well as photocatalytic properties. The TiSi₂/CQD nanohybrid photocatalyst was tested for the visible light (400 W LED lamp) driven photocatalytic degradation of eosin yellowish (EY) and Nile blue (NB), an anionic and a cationic dye, respectively. The TiSi₂/CQD photocatalyst showed excellent photodegradation efficiency of 83.7% (NB) and 95.1% (EY) as compared to TiSi₂. To mimic the real wastewater conditions, the TiSi₂/CQD photocatalyst was also tested with a mixture of two dyes (NB/EY) under direct natural sunlight conditions, with emphasis on the role of various parameters and their optimization (i.e., catalytic dosage, initial dye concentration and pH) in achieving the maximum degradation efficiency of 99%. The optoelectronic properties of TiSi₂ were enhanced by decorating its surface with CQDs acting as an electron reservoir and significantly improved the visible light absorption, photocurrent response and charge carrier-transfer dynamics while decreasing the electron–hole recombination rate. As a result, the TiSi₂/CQD composite showed excellent photodegradation with excellent recyclability up to three consecutive cycles. The kinetic studies showed that the photodegradation reactions followed the first order kinetics. This article introduces an economic, thermally stable and relatively non-toxic substitute for metal oxide-based semiconductor photocatalysts for excellent visible light activity.