Towards Durable, Selective Catalysts and Electrodes for CO2 Electroreduction to Value-Added Chemicals and Fuels

Abstract

Rising atmospheric carbon dioxide (CO2) levels and the associated rise in global temperatures are major global concerns. Annual atmospheric CO2 emissions have risen from about 2 Gt to 10 Gt in the last 5 decades.1 Electricity production and transportation are large atmospheric CO2 contributors (~70% of total emissions), and therefore scientists have developed renewable energies and fuel cells vehicles as a mitigation strategies.2,3 Another widely-studied mitigation approach is the electrochemical reduction of CO2 (CO2RR) to value-added chemicals and fuels. Depending on the electrocatalyst and operating conditions used for CO2RR, a variety of products including carbon monoxide, formic acid, ethylene, ethanol, and acetate can be made, which can serve as chemical feedstock for a variety of chemical processes.4 Most research on the CO2RR has focused on developing catalysts around four metrics: high product Faradaic efficiency (selectivity), high current density (activity), low overpotentials (high energy efficiency), and robust durability/stability. Product selectivity greatly affects economic feasibility (separation costs). Many groups have successfully concentrated on catalyst selectivity and activity. State-of-the-art catalysts for CO2 electroreduction can produce CO and HCOOH at high selectivity (>80%), but the selective production of high energy density hydrocarbons and oxygenates is still lacking.5 Moreover, increasing electrode and system durability aids in decreasing costs. Specifically, benchmarks set by technoeconomic analyses suggests system CO2RR lifetimes of >3000h.7,8 However, a majority of durability studies show lifetimes of <20h. In the first part of this talk, we will focus on developing selective electrocatalysts and defining their stability in an alkaline flow electrolyzer at ambient conditions. The second part of this talk addresses durability, specifically cathodes and the mechanisms by which they fail. With this, we explore strategies for developing more robust CO2RR cathodes and propose accelerated testing protocols to determine durability in a timely fashion. Acknowledgement We gratefully acknowledge financial support from Royal Dutch Shell, I2CNER and the SURGE Fellowship for UN. References Hansen, P. Kharecha, et al., PLoS One, 2013.Oerlemans, Science, 2005, 308(5722), 675-677.https://www.eia.gov Accessed 05/29/2017.R.M. Jhong, S. Ma, P.J.A. Kenis, Curr. Opin. Chem. Eng., 2013, 2, 191-199.J. Martin, G.O. Larrazabál, J. Pérez-Ramírez. Green Chem., 2015, 17(12), 5114-5130.Verma, B. Kim, H.R.M. Jhong, S. Ma, P.J.A. Kenis, ChemSusChem, 2016, 9(15), 1972-1979Jouny, W. Luc, F. Jiao, Ind. Eng. Chem. Res, 2018, 57(6), 2165-2177