BOOSTING LIGHT-DRIVEN PHOTOELECTROCATALYTIC WATER OXIDATION BY USING GREEN SOURCE-BASED CARBON QUANTUM DOTS

Abstract

The synthesis of carbon quantum dots (CQDs) from lignocellulosic waste is a sustainable, environmentally friendly, and low-cost alternative to produce very versatile carbon nanoparticles. Herein, we study the influence of conjugation of nickel tetrasulfonated phthalocyanine (NiTSPc) and green source-based CQDs in photoelectrocatalytic water splitting. The synthesized CQDs were characterized by Raman, infrared, ultraviolet-visible, and fluorescence spectroscopy, and transmission electron microscopy. For photoelectrocatalysis studies, working electrodes were produced over a glass covered with tindoped indium oxide (ITO) using the layer-by-layer technique. Cyclic voltammetry and chronoamperometry were used to evaluate the photoelectrocatalytic performance at dark and under blue and UV light irradiation. Under blue light, the current density of NiTSPc/CQD increased from 0.79 ± 0.03 µA cm-2 to 1.48 ± 0.11 µA cm-2 and under UV from 0.77 ± 0.10 µA cm-2 to 3.83 ± 0.23 µA cm-2 when turning on the UV light, which is 1.9 and 6.5 times the photocurrent of CQD15 and bare ITO, respectively. The increase in photocurrent density in the NiTSPc/CQD electrode may be associated with photogenerated holes in the valence band of PQC that oxidize water to oxygen. At the same time, the photogenerated electrons are transferred from CQDs to NiTSPc and then to the counter electrode. Thereupon, lignocellulosic residues, such as sugarcane biomass, are an excellent carbon source for facile synthesis of CQDs, offering a destination for this residue and presenting an environment-friendly nanomaterial for boosting light-driven photoelectrocatalytic water oxidation.