Blending ammonia in a syngas solid oxide fuel cell for carbon deposition improvement: Performance, electrochemical impedance spectra, and stability measurements

This paper reports how exactly blending ammonia in a syngas-fueled anode-supported solid oxide fuel cell (SOFC) improves carbon deposition at T = 650,700,750 °C using three anode fuels: (1) 200 sccm H 2 (baseline), (2) 200 sccm syngas (35%H 2 +65%CO), (3) 100 sccm syngas+50 sccm NH 3 , with the same cathode air flow rate of 200 sccm. Corresponding power densities (PD) at 0.68V rank as PD(1) > PD(2) > PD(3) at T = 650 °C, while PD(1) > PD(3) > PD(2) at T = 700,750 °C, indicating a higher ammonia decomposition rate at higher temperatures. Electrochemical impedance spectra are also measured and compared. We find serious carbon deposition in case (2), showing a precipitous fall of PD(2) at 350 mA cm −2 after only 2.5-h (650 °C) and 70-h (750 °C) of stable operation. As to case (3), PD(3) remains nearly constant during the whole 120-h stability tests, suggesting that ammonia can preferentially occupy the acid sites of Ni catalyst to avoid the coke formation.