Electrochemically Deposited Tin on High Surface Area Copper Foam for Enhanced Electrochemical Reduction of CO₂ to Formic Acid

Conversion of CO2 into valuable chemicals and fuels has received widespread attention as a way to tackle the increased CO2 emissions (Gattrell, Gupta and Co, 2006) and this also resulted in a reduction of dependence on fossil fuels . There are different techniques for CO2 conversion to value-added products, where electrochemical reduction (ECR) of carbon dioxide into chemical fuels is identified as a promising way since energy efficiency is high and the products, especially the chemical fuels can be readily stored. Among the variety of metallic electrodes, especially transition metals investigated for activity towards ECR of CO2, tin (Sn), bismuth (Bi), Indium (In) were found to be selective towards formic acid production. However, it was found that these metals show a low catalytic activity. To enhance the performance of CO2 reduction, three dimensional (3D) porous foam structured catalysts can be employed by increasing the active surface area. These 3D porous foam structures of metallic catalyst can be achieved by electrodeposition process by tuning the deposition parameters such that the evolving hydrogen during deposition can act as a dynamic template to fabricate 3D metal deposit structures with high surface areas (Shin, Dong and Liu, 2003). In this work, a 3D foam of copper is electrochemically deposited onto Cu foil (f-Cu) and Cu mesh (f-Cu mesh). Further, the deposition parameters for the electrodeposition of Sn on 3D Cu foam (Sn/f-Cu) were optimized to investigate the activity towards the ECR of CO2. SEM and EDX technique were employed for the physical characterization of the electrodes, while the produced formic acid from the reactions was quantified using ion chromatography. The results indicated that Sn/f-Cu mesh electrode showed better performance for ECR of CO2 to formic acid compared to Sn deposited copper foil (Sn/Cu) and bare copper foam. It was observed that Sn/f-Cu mesh achieved 83 % maximum faradaic efficiency at -1.6 V vs Ag/AgCl. However, a highest rate of formic acid production of 350 µmol/hr.cm2 was achieved at -1.8 V vs Ag/AgCl which is nearly seven times higher than Sn/Cu at the same potential. A similar analysis is going to be performed with the other formic acid selective catalysts like Bi/f-Cu mesh and In/f-Cu mesh. Based on the above analysis on faradaic efficiency against various electrodes, an optimized electrode will be identified and used in scaled-up electrolyser for CO2 reduction. References Gattrell, M., Gupta, N. and Co, A. (2006) ‘A review of the aqueous electrochemical reduction of CO2 to hydrocarbons at copper’, Journal of Electroanalytical Chemistry, pp. 1–19. doi: 10.1016/j.jelechem.2006.05.013. Shin, H. C., Dong, J. and Liu, M. (2003) ‘Nanoporous Structures Prepared by an Electrochemical Deposition Process’, Advanced Materials, 15(19), pp. 1610–1614. doi: 10.1002/adma.200305160.