Insights Into the Fuel Oxidation Mechanism of La[sub 0.75]Sr[sub 0.25]Cr[sub 0.5]Mn[sub 0.5]O[sub 3−δ] SOFC Anodes

Abstract

Solid oxide fuel cells (SOFCs) were fabricated by applying reproducible thin, dense La0.75Sr0.25Cr0.5Mn0.5normalO3−δ (LSCM) anode and La0.8Sr0.2MnO3−δ (LSM) cathode films to yttria-stabilized zirconia (YSZ) electrolytes by ultrasonic spray pyrolysis. A gold grid was applied to the anode film by lithography and plating, enabling adequate electrical contact while maintaining an open surface area for reaction. Alignment of the two electrode films and correct placement of the reference electrode enabled the separation of the anode and cathode impedance responses. Although the open-circuit voltage (OCV) of the LSCM|YSZ|LSM fuel cell at 700°C with humidified normalH2 fuel was close to that predicted by the Nernst equation, the anode polarization resistance was large (23Ω⋅cm2) . The addition of Pd to the anode film led only to a small decrease in polarization resistance, indicating that oxygen ion conductivity was the limiting factor for normalH2 fuel. The OCV for CH4 was close to that when an inert gas (He) was supplied to the anode. This OCV increased to 0.87 V upon addition of Pd to the LSCM film surface. This indicates that the bare LSCM film is limited by a low CH4 activation activity.

Ba-substituted LSCM anodes for solid oxide fuel cells

“…The sum of corresponding resistances R HF and R LF represents the polarization resistance R pol . This agrees with previous reports on LSCM based anodes in humidified hydrogen [43,44,58]. As shown in Fig.…”

“…In agreement with the shape of steady state curves, the polarization resistance decreases with increasing anode overpotential for both electrodes (Fig. 10), as already observed for porous perovskite based anodes [2,58]. At 850 C, R pol decreases by a factor of 3.5e3.7 between OCP and 0.4 V. The decrease of R pol is mainly due to that of the HF resistance for LBCM (not shown here).…”

“…The higher value determined for LBCM is rather close to that of oxygen diffusion in LSM [71]. The contribution of bulk transport to the oxidation reaction can be taken into account since the use of dense electrodes necessarily couples bulk transport and surface reaction [58].…”

“…Considering the influence of the oxygen ions flux in LSCM on the related anode behaviour [12,14], the re-oxidation of active sites is likely to occur by bulk ion transport in the perovskite phase, as clearly evidenced for a thin (w0.5 mm thick) and dense LSCM film [58]. Since the platinum paste and wires are located 4e5 mm away from the electrode/electrolyte interface (Fig.…”

Polarization-Induced Hysteresis in CuCo-Doped Rare Earth Vanadates SOFC Anodes

“…[1][2][3][4][5] One solution to this problem is to replace the Ni with an electronically conductive material that does not catalyze the formation of carbon from hydrocarbon fuels. Electronically conductive ceramics, including titanates, [6][7][8][9][10] manganates, [11][12][13][14] chromates, 15 and bronzes 16,17 have been investigated for this application. These materials have been shown to have a low susceptibility to sintering and coking and are more redox stable and tolerant of impurities, like sulfur, than Ni.…”