Pulsed Electrodeposition of Tin Electrocatalysts onto Gas Diffusion Layers for Carbon Dioxide Reduction to Formate
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Pulsed Electrodeposition of Tin Electrocatalysts onto Gas Diffusion Layers for Carbon Dioxide Reduction to Formate Sujat Sen,1 Brian Skinn,2 Tim Hall,2 Maria Inman,2 E. Jennings Taylor2 and Fikile R. Brushett1 1
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA 2 Faraday Technology, Inc., Englewood, OH, 45315, USA ABSTRACT This paper discusses a pulse electroplating method for developing tin (Sn)-decorated gas diffusion electrodes (GDEs) for the electrochemical conversion of carbon dioxide (CO2) to formate. The pulse-plated Sn electrodes achieved current densities up to 388 mA/cm2, more than two-fold greater than conventionally prepared electrodes (150 mA/cm2), both at a formate selectivity of 80%. Optical and microscopic analyses indicate improvements in deposition parameters could further enhance performance by reducing the catalyst particle size. INTRODUCTION The development of energy efficient carbon dioxide (CO2) electroreduction processes would simultaneously curb anthropogenic CO2 emissions and provide sustainable pathways for the generation of fuels and chemicals. While significant efforts have focused on heterogeneous CO2 electroreduction to various products, to date, few studies have demonstrated both high current efficiency (> 60 %) and high current densities ( > 150 - 200 mA/cm2) simultaneously [1-5]. A key challenge in the development of active, selective, and stable electrocatalysts is scaling performance nanomaterials to appropriate electrode structures, which augment catalytic activity by maximizing utilization, facilitating reactant/product transport, and minimizing undesirable side reactions. The electroreduction of CO2 to formic acid (FA) or its salts such as sodium formate, is attractive due to the low charge requirement (i.e., 2 electrons per FA), the liquid-state product, and the high product selectivity on a number of low-cost catalytic materials [6]. FA has a range of commercial uses including silage, textiles, leather tanning, pharmaceuticals, cropprotection, and latex processing [7]. It may also find use as a fuel for direct liquid fuel cells [8]. While a number of metals can be used for this reaction, tin (Sn) is of particular interest due to its high selectivity, low cost, and lack of toxicity [6]. The performance of Sn-based electrodes is largely dependent on the ability to efficiently deliver CO2 to the catalyst sites. Prior reports have demonstrated electroreduction of CO2 to FA on Sn catalysts at varying current efficiencies (10-95%) on disk electrodes, metal meshes, and gas diffusion electrodes (GDEs) which operate at a range of currents (10-200 mA/cm2) depending on modes of CO2 transport [6, 7, 9-13]. In addition, recent work has shown that product selectivity decreases with increasing catalyst loading likely due to mass transport losses within a thick catalyst layer [10]. Thus, there is a need to investigate new approaches to electrode development that maximize performance in terms of product generation rate, selectivity, and cata
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