Minimizing Coke Formation at La 0.3 Ca 0.7 Fe 0.7 Cr 0.3 O 3-δ Perovskite Anodes in a Syngas Fed-SOFC

As the world moves to decarbonize the fossil fuel sector, transition technologies are needed that bridge the gap between natural gas power plants and more sustainable low-carbon energy sources. These newer technologies often still rely on fossil fuels but have improved energy conversion efficiencies and lower net carbon dioxide (CO 2 ) outputs over conventional fossil fuel based electric power generation systems. In this work, we are exploring one such technology, namely the use of a syngas-fed solid oxide fuel cell (SOFC) to generate heat, electricity, steam, and captured CO 2 . Core to this technology is the mixed ion electron conductor deployed at the anode and cathode that catalyzes all of the relevant reactions, namely electrochemical oxidation of hydrogen (H 2 ) and carbon monoxide (CO) at the anode, producing steam and CO 2 , and reduction of oxygen at the cathode. Carbon formation (coking) is normally a significant problem affecting SOFCs operating on carbon-based fuels, as it leads to a rapid decline in electrochemical performance by blocking catalytically active sites and pores with various carbon species, e.g., amorphous, graphitic, or nanotubular carbon. 1 The formation of carbon species from syngas is known to occur through various mechanisms, with the Boudouard reaction (∆H= -172 kJ/mol) and the reduction of CO (∆H= -131 kJ/mol) being the most prominent. 2 As such, temperature is a key parameter to optimize as it determines the propensity for carbon formation at equilibrium. In addition, the kinetics of carbon formation can be significantly reduced by introducing oxygen to the fuel gas stream in the form of O 2 , CO 2 , or H 2 O. 3 The catalyst materials investigated here are mixed conducting perovskite oxides (La 0.3 Ca 0.7 Fe 0.7 Cr 0.3 O 3- δ , LCFCr) that have been optimized and modified recently by our group, both in the as-prepared undoped form and after B-site doping with variable quantities of transition metals (M), e.g., Ni, 4 forming nanoparticle (NP)-decorated ABO 3 -M x surfaces. Our catalyst is highly active for H 2 and CO oxidation, CO 2 reduction, and O 2 reduction, where it was demonstrated that the un-doped parent material can deliver a stable power density of 0.2 W/cm 2 for several hundred hours with negligible performance degradation in 3% humidified H 2 . 5 In more recent work, excellent resilience to carbon deposition for exsolved Fe-Ni@LCFCr up to 70:30 CO:CO 2 was demonstrated. 4 Herein, we show that minimal coke forms