Testing novel nickel and cobalt infiltrated STN anodes for carbon tolerance using in situ Raman spectroscopy and electrochemical impedance spectroscopy

摘要

Conventional SOFCs use Nickel Yttria-doped Zirconia cermet (Ni-YSZ) anodes because they are effective, durable and inexpensive electrocatalysts. However, these same materials are also susceptible to degradation due to coking from carbon accumulation when operating with carbon containing fuels. Raman spectroscopy is a powerful tool for investigating surface chemistry and, when combined with electrochemical impedance spectroscopy (EIS) under in situ conditions, the technique can report the real-time material composition of the electrode during the EIS measurements. Studies described in this work used in situ Raman spectroscopy and electrochemical impedance spectroscopy to examine the carbon tolerance of novel ceramic anode materials comprised of niobium doped strontium titanate (STN) infiltrated with either nickel or cobalt nanoparticles. The susceptibility of these electrodes to coking were tested with CO/CO2 mixtures and pure methane at 850?C. Data show that nickel infiltrated STN electrodes are still prone to coking from methane. In contrast to STN electrodes infiltrated with nickel, cobalt infiltrated STN electrodes showed no susceptibility to carbon deposition within the detection limit of the Raman measurements during methane exposure. Neither anode showed evidence of coking from the CO/CO2 mixtures. Coking correlated closely with changes in EIS measurements, with the most noticeable effects appearing in the low frequency part of the spectrum. Ex situ SEM analysis of samples before and after the usage illustrated how operational conditions influence electrode microstructure leading to the agglomeration of the nanoparticles.