Effect of Ca2Fe2O5 catalyst on the performance of DC-SOFC with semi-coke fuel

Abstract

Semi-coke is an excellent candidate fuel for direct carbon-solid oxide fuel cell (DC-SOFC), and its gasification reaction rate with CO2 is the key factor that effects the performance of DC-SOFC fueled semi-coke. In order to improve the gasification reactivity of semi-coke with CO2, the Ca2Fe2O5 catalyst with perovskite structure has been prepared using citric acid sol-gel method. The morphology and structure of the Ca2Fe2O5 catalyst has been investigated using SEM, XRD, XPS, low-temperature nitrogen adsorption-desorption methods. The catalytic activity of Ca2Fe2O5 catalyst in the gasification reaction of semi-coke with CO2 has been studied by thermogravimetric measurements. The effect mechanism of the semi-coke fuel added Ca2Fe2O5 catalyst on the output performance of DC-SOFC has been investigated using Ag-GDC|YSZ|GDC-Ag electrolyte supported DC-SOFC. The results indicate that as the calcination temperature of the catalyst increases, the grain size of Ca2Fe2O5 catalyst gradually increases and the specific surface area decreases. The catalyst calcined at 750 ℃ has good dispersibility and a particle size of approximately 0.1 μm exhibits the best catalytic activity in the gasification reaction of semi-coke and CO2. Compared to the CaO and Fe2O3, the Ca2Fe2O5 catalyst structure has a higher concentration of adsorbed oxygen, which is more conducive to its catalytic effect. In the gasification reaction of semi-coke and CO2, the cyclic stability of Ca2Fe2O5 catalyst depends on the thermal stability of the catalyst structure. During the cyclic use of the catalyst, the decrease in catalytic activity is mainly attributed to the encapsulation of inorganic ash in the semi-coke fuel. Research on the performance of DC-SOFC shows that when 10% Ca2Fe2O5 catalyst has been added to the semi-coke, the peak power density of the cell increases from 15.3 mW/cm2 to 23.7 mW/cm2. The EIS analysis shows that the anode mass transfer resistance is the main factor affecting the output performance and fuel utilization of DC-SOFC. Reducing the mass transfer resistance caused by the accumulation of ash and catalyst can effectively improve the DC-SOFC life and fuel utilization.

Keywords

• direct carbon-solid oxide fuel cell
• perovskite
• catalyst
• c-co2 gasification reactivity