Arc-Driven in Situ Fabrication of Titanium Suboxide Composite with Graphene from Waste Biomass and Its Electrochemical Applications

Substoichiometric TiO2, also known as titanium suboxides (TSOs), is identified as a series of compounds with a chemical composition of TinO2n–1 (4 ≤ n ≤ 10). They are widely recognized as materials with high electrostability and excellent electrochemical activity. However, making a TSO composite material such as TSO-graphene through traditional multi-step and expensive methods is tedious and has poor scalability. In the current work, we demonstrated an in situ fabrication of arc-driven graphene-titanium suboxide composites (ADG-TSO) in a chemical-free, cost-effective, and sustainable way utilizing TiO2 mixed with waste leaf biomass. This method directly converts TiO2 and carbonaceous waste biomass into TSO-graphene composites via high-current resistive heating through an arc-driven process by using an arc generator machine. The graphene-TSO composite formation was confirmed through various spectroscopy techniques, revealing the formation of a series of TSO compounds such as Ti8O15, Ti3O5, and Ti2O3 upon the arcing process. Furthermore, the conductive ADG-TSO powder with various compositing concentrations of 2.5%, 5%, and 10% was vacuum-deposited on a surface, demonstrating enhanced electrochemical activity with 5% ADG-TSO outperforming all others. These coated surfaces also demonstrated enhanced electrochemical removal of CIP with ADG-TSO (5%) composite surface, showing higher removal of ∼85% at 5 V in flow-through mode and ∼55% within 1 h at 5 V in batch mode. Nonetheless, this cost-efficient and easy fabrication of ADG-TSO conductive material offers a sustainable process for graphene fabrication from biomass waste as well as an in situ conversion of TiO2 to TSO. This approach provides economic and environmental benefits and helps to achieve sustainable development goals through a circular economy.