Hydrochar from Carbon Quantum Dots (CQDs) Synthesis for Photocatalytic and Decontamination Applications in Presence of TiO2

Abstract

This research aimed to co-produce CQDs and hydrochar from natural sources to improve the photocatalytic properties of TiO2. Juice extract from Citrus lemon fruits from south-eastern Spain was used as the carbon precursor. The synthesis strategy of the CQDs and hydrochar (Hc) was divided into different stages aimed at figuring out the role of the temperature (180, 220, 250 °C), the addition of TiO2 nanoparticles, and the presence of N-/P-donor compounds (ethylenediamine and orto-phosphoric acid) in the photocatalytic properties of final composites. The results revealed that at 250 °C, using agro-carbon materials as Hc, and the addition of N-donor compounds, improved the photocatalytic activity and photodegradation rate of TiO2 over methyl orange (MO) under blue light by 1000% and 2700%, respectively, with the parallel reduction of TiO2 bandgap from 3.5 eV (Uv light) to 3.00 eV (visible light). These results are related to the ability of the carbon materials (electronegative) to enhance the formation of a Ti3+-active state. This study provides a landscape for a one-step method for the production of agro-carbon/TiO2 photocatalysts with high activity under visible light as an efficient and sustainable strategy for applications such as energy generation and water purification under sunlight.