Carbon Nanotube-Based Electrolyzers

Abstract

In this study, an innovative methodology for fabricating carbon nanotube (CNT)-based electrodes for water splitting is presented using C-silk carbon nanotubes developed by Lintec of America. The process initiates with the solid-state dry spinning of drawable CNTs onto supports such as commercial carbon fiber (1K twill). This fabrication technique, initially manual and later automated for consistency, involves varying the number of CNT layers and employing a solvent densification method using ethanol to achieve a structurally reinforced configuration. Following this, the electrodes undergo a covalent functionalization process using a 1:1 by volume HNO3/H2SO4 to enhance electrocatalytic activity by introducing functional groups on the CNT surface. The structural and morphological characteristics of the electrodes are meticulously analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR). Electrochemical behavior is assessed through linear sweep voltammetry (LSV) in a 0.5 M H2SO4 electrolyte using a three-electrode system to evaluate the performance in hydrogen evolution reaction in terms of overpotential, Tafel slop and polarization resistance. This comprehensive approach leverages the unique properties of CNTs to fabricate electrodes with potentially enhanced performance for water splitting, incorporating innovative techniques like air spraying graphene oxide (GO) for improved structural integrity and electrocatalytic efficiency. The research highlights that a 50-layer CNT electrode configuration yielded high electrical conductivity 44,724.5 S/m. The lowest overpotential was associated with the electrode which is 1%GO/CNTs which required -0.649 V vs. RHE @ 10 mA/cm2 for HER in 0.5 H2SO4. Additionally, the best among the acid treated electrode was that with 30 min treatment time requiring -0.664 V vs. RHE for the same conditions. This is due to the addition of functional groups such as hydroxy and carboxyl groups making the electrode surface hydrophilic as evident by the water contact angle measurements.

Date of Award	9 May 2024
Original language	American English
Supervisor	Ludo Dumee (Supervisor)