General, Metal-free Synthesis of Carbon Nanofiber Assemblies from Plant Oils

We designed a metal-free synthesis of carbon nanofiber based on ketene chemistry using phosphorus pentoxide (P₂O₅) and vegetable oil. Based on the characterization of intermediates, P₂O₅-oil reaction yielded most possibly alkylketenes, which polymerized into poly(ketene) with abundant enol groups. The enol groups further reacted with P₂O₅, forcing the poly(ketene) to assemble into a nano-sized preassembly structure. Moderate heating transforms these structures into carbonaceaus nanofibers. This approach is applicable to other chemicals with similar structure to vegetable oil. The carbon nanofibers with P-O-C functionalization show relatively high graphitization degree and promising textural properties. The C-O-P environment accounts for 66 at % of the total P and creates a superior thermal stability. As a model application, a CDI system built of a carbon-nanofiber-based electrode countered by an activated carbon-based electrode exhibited exceptional performance.