Electrochemically Fabricated Binary Alloy Catalysts for CO2-C1 Fuel Inter-Conversion

Abstract

Electrochemical reduction of carbon dioxide to useful chemical has been studied as a promising method to utilize CO2. This method can selectively produce a variety of useful chemicals (e.g. carbon monoxide, formic acid, methane, and other hydrocarbons) according as reaction condition such as types of electro-catalysts, electrolytes, operation voltage, and so on [1,2]. In this study, we selected formate as a target product because it has various advantages as a feed stock chemical. Formate is produced by the electrochemical reduction of the CO2 and the formate, after treatment to form formic acid, will be used as fuel for Direct Formic Acid Fuel Cell. Particularly in the case of CO2-based unitized re-generative fuel cell, the inter-conversion reaction between CO2-C1 fuels is important. Therefore, we develop a catalyst that can be used in both sides reaction; the electrochemical conversion of CO2 to formate and the oxidation of formic acid [3]. In this case, it is most important to develop bi-functional catalysts that have activities for both reactions. In addition, high selectivity and activity to CO2 reduction as well as reduced amounts of noble metal loading for the formic acid oxidation reaction are also desired. The catalysts were made by co-electrodeposition of noble metal and post-transition metal to form binary alloy catalysts. Electrodeposition was performed at a constant deposition potential in a 3-electrode cell containing metal precursors, supporting electrolyte, and complexing agent. For some cases, thermal annealing was performed to enhance the characteristics of the fabricated catalysts. The alloy catalysts were characterized with EDS, SEM and XRD. The electrochemical reduction of carbon dioxide was performed and the produced amounts of formate were measured with HPLC. Formic acid oxidation was also performed with CV using the same catalysts. The activities to both reactions were characterized according to the alloy composition, morphologies, and other physic-chemical properties. In conclusion, certain composition of the alloy catalysts exhibited the significant activities to both reactions simultaneously.