Nitrogen Enhanced Boron-Doped Diamond Films for Superior Electrochemical Supercapacitors

Diamond thin films have gained popularity as energy storage device materials due to their robust mechanical and chemical properties, as well as their extended lifetime stability [1]. Numerous investigations have been conducted on supercapacitors made of boron-doped diamond (BDD) with varying diamond morphologies. Nevertheless, the impact of diamond grain size and structure on electrochemical performance has yet to be comprehensively understood. In the present work, BDD films of 4 different morphologies, obtained via varying the growth temperature (400⁰, 550⁰, 700⁰ and 850⁰C), have been studied and compared. The increase in substrate temperature during the growth of diamond film varies from faceted structures (400⁰C) to nanowire-like structures (850⁰C). The variation in grain structure has a direct impact on the electrochemical behaviour of supercapacitors [2]. For the nanowire diamond, the specific capacitance is 412 µF/cm² at a current density of 2.55 µA/cm²in 1M Na₂SO₄, which is the maximum. The loss in specific capacitance for the 400⁰C sample is found to be 30%, whereas the loss decreases with an increase in growth temperature and is 19% for the 850⁰C sample. Such efficient nature of the material can be attributed to the nanowire-like structure, boron doping and induction of sp²-graphitic grain boundaries, which enhance the electrical conduction and the interaction area, in turn enhancing the electric double layer capacitance (EDLC) value and the lifetime stability of the electrochemical supercapacitor system. These results indicate that the nitrogen-enhanced BDD nanowire films will pave a pathway for the next-generation electrochemical supercapacitors.<br/><br/><b>References:</b><br/>[1] Nianjun Yang, S. Yu, J. V. Macpherson, Y. Einaga, H. Zhao, G. Zhao, G. M. Swain, X. Jiang, Chem. Soc. Rev. 48, 157 (2019).<br/>[2] S. Suman, M. Ficek, K. J. Sankaran, J. Ryl, Benadict Rakesh, M. Gupta, R. Sakthivel, R. Bogdanowicz, Energy 294, 130914 (2024).