Synthesis, Characterization and Application of Zinc Complexes in Photocatalytic Fuel Cell (PFC) for Wastewater Treatment and Generating Electricity

Nur Syahidda Ani, Moksin (2022) Synthesis, Characterization and Application of Zinc Complexes in Photocatalytic Fuel Cell (PFC) for Wastewater Treatment and Generating Electricity. Masters thesis, Universiti Malaysia Sarawak.

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Abstract

Photocatalytic fuel cell (PFC) is a water treatment technology which can treat wastewater and generate electricity simultaneously. This speciality has drawn vast attention from researchers and also the industrial sectors. However, although the efficiency of degrading organic pollutant by the system is often high, the amount of electricity generated was still scarce and insufficient electrical energy was harvested. The main reason was that the application of commercialized photocatalyst in PFC has restricted further analysis in band gap energy (Eg) which associated with the efficiency of a photocatalysis. Therefore, this study aimed to investigate the relationship between the Eg and the overall efficiency of PFC by applying ligand field theory (LFT). Firstly, the standard photocatalyst, ZnO, was used as photoanode in the PFC to treat diluted palm oil mill effluent (POME). The chemical oxygen demand (COD) removal efficiency was 93.75% and the maximum power (Pmax) generated was 38.85 µW/cm2 after 6 hours operation at pH 7 under 1300 lx light intensity. Later, three metal complexes were synthesized in this study, namely diacetylacetonatozinc(II) complex, [Zn(acac)2], di(1,10-phenanthroline)zinc(II) chloride complex, [Zn(phen)2]Cl2 and dichlorobis(triphenylphosphine)zinc(II) complex, [ZnCl2(PPh3)2] and dopped on a Zn plate as the photoanode in their respective PFC system. These zinc complexes were synthesized with pi-donor ligand, acetylacetonato (acac) as well as pi-acceptor ligand, namely 1,10- phenanthroline (phen) and triphenylphosphine (PPh3) to alter the Eg of the photocatalyst used. PFC system fabricated by aforementioned complexes were compared to a standard ZnO/Zn PFC with diluted palm oil mill effluent (POME) as the electrolyte. All of the PFC systems were optimized with parameters such as contact hour, initial organic pollutant concentration, initial pH value and light intensity. Results showed that the overall efficiency of [Zn(phen)2]Cl2/Zn PFC surpassed ZnO/Zn with 96.29% COD removal efficiency and Pmax v generation of 48.76 µW/cm2 at pH 6, under 1300 lx light intensity for 4 hours. The least efficient system in this study was found to be [Zn(acac)2]/Zn with COD degradation at only 44.78% and Pmax of 9.33 µW/cm2 at pH 6 , under 1300 lx light intensity for 2 hours. The overall efficiency of these complex was found to be correlated with the estimated Eg, as the smaller the Eg the higher the efficiency of the PFC system in both degrading organic pollutant and generating electricity. Keywords: PFC, photocatalysis, POME treatment, zinc complexes, band gap energy

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