RPG Student List


Khak Ho LIM

Doctor Candidate in Chemical and Biomolecular Engineering

Supervisor: Prof. Ka Ming NG


Research Topic

Synthesis and Characterization of Hybrid Organic-Inorganic Thermoelectric Materials


Thermoelectric (TE) materials have drawn researchers’ attention in recent decades for use as an alternative green energy source, due to the limited natural resources and rising demands for reduction of CO2 emission. Current TE materials usually involve expensive and toxic inorganic heavy metals, thus high material and processing costs, yet less than satisfactory performance. A hybrid of electrical conducting polymer-poly(3,4-ethylenedioxythiophene) (PEDOT) and inorganic nanomaterials (NMs) is of high interest due to the synergistical coupling of the individual properties of PEDOT and NMs. This thesis is, therefore, aimed to synthesize a TE material based on this hybrid structure that has a high figure of merit (ZT). The effects of molecular orientation and morphology of PEDOT and its polymer composite, has been investigated in Chapter 1. Nanofibres of PEDOT have been fabricated and mixed with PMMA. The morphological effect contributing to the thermoelectric effect was investigated. An in-house setup has been built for the TE characteristic studies.
Four phases of sulphur- containing chalcogenides was studied in Chapter 2. These 4 phases of sulphur -containing chalcogenides was investigated and compared. Surface modifications on the best phase of nanoparticle has been performed and their relevant TE performance have been investigated. The best-performing phase with the surface ligand that yield the highest TE performance has been selected as the candidate for the next organic-inorganic hybrid studies.
Synergistic effect of the polymer, hybrid with four phases of sulphur-containing chalcogenides on TE properties will be investigated in Chapter 3. Hybrid material of PEDOT and four phases of sulphur- containing chalcogenides is predicted to have superior performance than neat PEDOT. The energy dependent scattering, phonon scattering and non-energy dependent scattering of this hybrid material will be further evaluated.
In Chapter 4, a new family of n-type nanomaterial will be synthesized and tuned to achieve high TE performance. As contrary to previous Chapters, this n-type material will be evaluated by using thin film method, to fabricate thin film device with high TE performance. A complete p-n type TE device aiming to harness low-grade heat will also be produced and evaluated in this Chapter.