Modification of glassy carbon electrode (GCE) surface with carbon nanotubes and carbon composites is an active area of research within electrochemical applications such as biosensor[1,2], fuel production[3], and energy storage[4], etc. Reactivity and characteristics of GCE is improved/controlled by surface modification. Chemical/electrochemical modification of multiwalled carbon nanotubes (MWCNT) with various mediators such as organic molecules, polymers, and metal organic frameworks, etc., are established as a cutting edge research in recent days towards improving the structural and electronic properties of the electrode. This will be helpful in tweaking the electrocatalytic properties at the surface of the electrodes.
This colloquium aspires on electrocatalysts for detection of biomolecules, and electrochemical reduction of small molecules such as oxygen and nitrogen in the context of sensor, energy conversion and storage. In the course of this work, GCE was modified using various developed electrocatalysts. The colloquium encompasses four chapters. Chapter 1A demonstrates the unconventional endohedral filling of MWCNT with various solvents for simultaneous detection of ascorbic acid, dopamine, and uric acid. Endohedrally filled MWCNT exhibit remarkably enhanced characteristics for sensor applications. The detection threshold being lowered by as much as an order of magnitude, while detection sensitivity is doubled to that of unfilled MWCNT. Chapter 1B deals with the non-covalent surface modification of MWCNT using 1-amino 2-naphthol to detect ascorbic acid (AA) with minimal overpotential and good selectivity. The reduction in the overpotential possibly due to the coulombic interaction between the oxidized form of 1N2OH with ascorbate anion facilitates electron tunneling between MWCNT and AA.
Chapter 2 discusses the formation of bisbenzimidazolatocopper(II) film on MWCNT and the same was utilized for the electrochemical estimation of hydrogen peroxide (H2O2). The electrode exhibited a H2O2 detection limit of 7.8×10-7 M and the sensitivity of 5 nA/μM. Chapter 3 focuses on the surface modification of MWCNT by assembling copper-benzotriazole through π-π interaction, which was identified as a remarkable electrocatalyst for oxygen reduction reaction (ORR) through four electron pathway. The observed Tafel slope (~69 mV dec-1) and higher exchange current density (1.73×10-4 mA cm-2) indicate the faster kinetics of ORR. Chapter 4 discuss about nitrogen reduction on two different material. In chapter 4A, spent primary battery material was converted as electrocatalysts (ZnMn2O4) for electrochemical nitrogen reduction. In aqueous medium, the achieved a faradaic efficiency of 13.3 % at -0.5 V vs. RHE with ammonia yield rate of 33.8 µg h-1 mgcat-1. In chapter 4B non loading electrocatalysis method is employed for N2 reduction. 0.5 mM of [Ni6(PET)12] cluster is dissolved in THF medium, which catalyze nitrogen adsorption and electron/proton transfer alone occurs at the electrode/electrolyte interface. A NH3 production efficiency of 25.8 % is obtained at -2.6 V vs. Fc+/Fc.
References
[1] Y. Yun, Z. Dong, V. Shanov, W.R. Heineman, H.B. Halsall, A. Bhattacharya, L. Conforti, R.K. Narayan, W.S. Ball, M.J. Schulz, Nanotube electrodes and biosensors, Nano Today. 2 (2007) 30–37.
[2] J. Wang, Carbon‐nanotube based electrochemical biosensors: A review, Electroanal. An Int. J. Devoted to Fundam. Pract. Asp. Electroanal. 17 (2005) 7–14.
[3] R. Orinakova, A. Orinak, Recent applications of carbon nanotubes in hydrogen production and storage, Fuel. 90 (2011) 3123–3140.
[4] L. Sun, X. Wang, Y. Wang, Q. Zhang, Roles of carbon nanotubes in novel energy storage devices, Carbon N. Y. 122 (2017) 462–474.