Catalyst Development and Reaction Pathway Study of Copper Oxide for Glycerol Electro-Oxidation Reaction

• Main Authors: Chin Liu, 劉謹
• Other Authors: Chia-Ying Chiang
• Format: Others
• Language: en_US
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/585rk9

碩士 === 國立臺灣科技大學 === 化學工程系 === 107 === Low-cost and high-efficient copper oxide, CuO, was used as an electrocatalyst for glycerol electro-oxidation reaction (GEOR). Copper oxide showed the onset potential of 1.25 V vs. RHE for GEOR in pH 13. High-performance liquid chromatography (HPLC), Raman spectroscopy and electrochemical method were used for analysis the products of GEOR. Considering that reactant adsorption, intermediate formation to product desorption are critical, HPLC was used for analyzing the product distribution in the bulk liquid while the in-situ Raman spectroscopy was employed to detect the surface reaction on the solid electrode. Accordingly, dihydroxyacetone (DHA), glycerate, glycolate, oxalate, and formate were detected quantitatively by HPLC. Interestingly, it was found that the product selectivity can be controlled by tuning the properties of the applied potential and solution pH. At the lower applied potential of 1.29 V vs. RHE in pH 13, three-carbon (C3) products have a higher selectivity, i.e. 26% for glycerate and 5% for DHA. However, C-C bond cleavage at higher potential was observed which lead to the formation of vast amount of formate and carbonate. From In-situ Raman spectroscopy, we found that the reaction pathway of GEOR in pH 13 by CuO catalyst started from the oxidation of secondary hydroxyl group, leading to the formation of DHA, and DHA spontaneously transferred to glyceraldehyde (GLAD). GLAD then oxidized to glycerate and continued the higher oxidation degree products. Lowering the pH to pH 9 can slow down the transformation of DHA to GLAD, thus, the ability of selective oxidation of glycerol to DHA (~60% selectivity) can be easily observed.