Upcycling real world tyre waste into carbon nanosheets and investigating their electrocatalytic performance for oxygen reduction reactions

• Main Author: Ng, Jun Eng
• Other Authors: Grzegorz Lisak
• Format: Final Year Project
• Language: English
• Published: 2019
• Subjects: DRNTU::Engineering::Environmental engineering::Waste management
• Online Access: http://hdl.handle.net/10356/78465
• Institution: Nanyang Technological University

Waste tyres can pose serious environmental problems if not handled properly. Pyrolysis is one way that countries use to treat their waste tyre streams, converting the tyre rubber into pyrolytic oil, char, and pyrolytic gas. While these products can be reused as fuel or as intermediaries for manufacturing, the low value of the products does not justify the high costs due to the energy demand of pyrolysis. The chemical vapour deposition process is one method in which research has been done to upcycle tyre pyrolysis products, and valuable carbon nanomaterials have been formed in numerous studies. As such, this study was conducted to investigate 1) the potential of using non-condensable pyrolysis gas from waste tyre pyrolysis for synthesis of carbon nanomaterials using catalytic chemical vapour deposition (CVD) and 2) the electrocatalytic activity of the synthesised carbon nanomaterials for oxygen reduction reaction. In this study, waste tyre pyrolysis was carried out at 600°C. The evolved non-condensable pyrolysis gas was passed into a catalytic reactor containing NiO-loaded CaCO3 as a catalyst for CVD synthesis of carbon nanotubes. Temperatures used for CVD were varied from 650 to 800°C. It was discovered that carbon nanosheets were synthesised, with the highest yield at 750°C. As tyre rubber contains sulfur in its elemental composition, it was theorised that S-doping of the carbon nanosheets might occur during catalytic CVD. Additional N-doping of the synthesised materials was also carried out with a saturator that mixes the non-condensable pyrolysis gas with aqueous ammonia before CVD. The carbon materials were examined using XPS and it was confirmed that N and S doping did occur in the nanosheets with O, S dual-doped and O, S, N tri-doped nanosheets formed. The electrocatalytic performances of the doped carbon nanosheets were evaluated using linear sweep voltammetry (LSV) with Ag/AgCl/saturated KCl as a reference electrode and it was discovered that the carbon nanosheets catalysts synthesised in the 600-750°C temperature range all had similar peak potentials that were only slightly higher than the commercially used Pt/C electrodes.