Effects of nitrogen incorporation on N-doped DLC thin film electrodes fabricated by dielectric barrier discharge plasma: Structural evolution and electrochemical performances

Abstract

Hydrogenated amorphous carbon-nitride (a-C:H:N) thin films (or N-DLC) were deposited on glass and FTO substrates by a dielectric barrier discharge plasma technique using CH4/N2 gas mixture. The XPS results reveal that as the nitrogen ratio in the CH4:N2 gas mixture increases from 50% to 80%, the nitrogen doping level increased from 5.5 at.% to a maximum value of 11.5 at.% with especially high amounts of pyridinic (6.4 at %), and graphitic (4.7 at %) nitrogen. FEG-SEM results indicate a worm-like porous morphology for the 20%:80% CH4:N2 sample, relying on high amounts of pyridinic and graphitic N, which is a favorable structure to boost the ions diffusion process. This optimized N-DLC electrode with high nitrogen incorporation not only exhibits a nearly electrochemical reversibility with ΔEp (125 mV) and Jpa/Jpc (1.03) in K3Fe(CN)6 electrolyte, but also a fast charge transfer constant (6.59 × 10−4 cms−1). The excellent performance of this electrode is ascribed to the high nitrogen doping level, large surface area, the abundant holes, and the high nano-pore volume possessing excellent electron transfer ability for redox reaction. N-DLC thin film exhibits a promising prospect for biosensors and electrochemical electrode applications.