| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 106 === Photoelectrochemical water splitting is using solar energy to convert water into H2 and O2. By doing so, we might be potentially to solve the two major problems, i.e. energy shortage and environmental pollution, at the same time. In this study, we use BiVO4 as photoanode, which has a relatively small band gap (~2.5 eV) and thus it can absorb sun light effectively. However, it has shortcomings of poor electron conductivity and slow water oxidation kinetics. In order to boost the overall efficiency, we use glycerol, a by-product from biodiesel manufacture, as a sacrificial agent to replace water oxidation by glycerol oxidation. As a result, hydrogen can be still produced at the cathode while at the anode, glycerol is converted into other more valuable products.
BiVO4 film grown on FTO via a facile spin-coating method was employed as photoanode. The photocurrent density in the electrolyte with the introduction of glycerol is much higher than that without glycerol. The onset potential shifts towards less positive potentials as glycerol introduced. With 2.0 M glycerol in solution under 1.23 V vs. RHE, the hole injection yield of 140% is observed due to the Current Multiplication effect. The photocurrent density boosts to 1.28 mA/cm2 which is more than 3.8 times higher as that of 0.33 mA/cm2 for water oxidation.
We observed good stability for BiVO4 electrode in 0.1 M glycerol solution after 3 hrs reaction at 0.7 V vs. RHE. The product analysis results show the amount of H2 detected from cathode is close to the theoretical calculation, and the main products from glycerol oxidation are formic acid and dihydroxyacetone with the selectivity of 15% and 85%, respectively.
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