Oxygen Reduction Characteristics on Ag, Pt, and Ag-Pt Alloys in Low-Temperature SOFCs

Huang, Hong; Holme, Tim; Prinz, Fritz B.

doi:10.1149/1.2789268

Cited by 25 publications

(23 citation statements)

References 23 publications

(43 reference statements)

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“…It is well known that Pt is a better catalyst than Ag for oxygen to be reduced to lattice oxygen when SDC is used as the electrolyte for oxygen ion conduction in SOFCs. 39,40 In agreement with this, oxygen fluxes of S-V (in Fig. 4) could be observed with appreciable values at much lower temperatures than that from S-IV due to the better catalytic efficiency of Pt.…”

supporting

confidence: 79%

Novel CO₂-tolerant ion-transporting ceramic membranes with an external short circuit for oxygen separation at intermediate temperatures

Zhang

Shao

et al. 2012

Energy Environ. Sci.

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Here we report a new concept for oxygen separation by the oxygen ion conducting ceramic membrane with an external short circuit. With the strong chemical stability against acidic gases like CO 2 and the higher oxygen fluxes at lower temperatures, this novel membrane concept could possibly result in a breakthrough for tonnage oxygen production to improve the viability of these clean energy technologies.Global climate change is challenging the existing power generation system and new clean energy delivery technologies with reduced CO 2 emissions are urgently required. Among the promising options to integrate the existing coal-fired power stations with CO 2 capture to produce low emission electricity, oxyfuel combustion seems to be more feasible than other options and several big projects have been initiated in the world such as CS Callide (Australia), Vattenfal (Germany), Inabensa (Spain), OXY-CFB-300 (Spain), TotalLacq (France) and FutureGen2 (USA) program with billion dollar investments for each of these projects. Under the oxyfuel concept, coal will be fired with pure O 2 or an O 2 /CO 2 mixture instead of air; the major constituent of the waste gas produced during the new combustion process is highly concentrated CO 2 enabling its capture more economically feasible. 1-5 However, all these oxyfuel combustion projects are still in the demonstration stage and cannot compete commercially with the conventional air-fired coal power plants because of the significantly high investment and operation costs. Among the basic operational units of the oxyfuel combustion, the complex air separation unit (ASU) via the cryogenic method to provide pure oxygen is the most expensive section, accounting for approximately 50% of the overall CO 2 capture cost. 6,7 Addressing this concern to reduce the cost, oxygen ionic conducting ceramic membranes have received increasing attention because they are envisaged to replace the cryogenics and reduce O 2 production cost by 35% or more, offering the potential to tackle these energy penalties and improve the viability of zero emission technology. 8-12 However, these membranes must possess sufficiently high oxygen permeability and structural stability to withstand the real process conditions which include the presence of highly concentrated CO 2 .The two main categories of ionic transport ceramic membranes for oxygen separation attracting intense attention are pure oxygen ion conducting membranes 13,14 and mixed ionic-electronic conducting (MIEC) membranes. [15][16][17][18][19][20][21] For the pure ion conducting membranes with the concept schematically shown in Fig. 1A, an external power source and electrodes are required to provide the electric current. Driven by the electrical potential gradient, the oxygen transport can be precisely controlled in quantity by applying the electric current so the oxygen can be pumped in either direction regardless of the oxygen

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confidence: 79%

Novel CO₂-tolerant ion-transporting ceramic membranes with an external short circuit for oxygen separation at intermediate temperatures

Zhang

Shao

et al. 2012

Energy Environ. Sci.

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“…1 It is desirable to operate SOFCs at lower temperatures, although at lower temperatures perovskites do not have sufficient catalytic activity and produce large voltage losses, 2 thus new catalysts are actively being sought. 3 Recent SOFCs may produce over 1.3W/cm 2 at below 500 °C, but must use short-lived Pt catalysts to achieve such high performance. 4 In proton exchange membrane (PEM) fuel cells, platinum is a popular catalyst, and alternatives are usually platinum alloys with high Pt content.…”

Section: Introductionmentioning

confidence: 99%

“…Typical solid oxide fuel cells (SOFCs) are operated at temperatures above 700 °C, at which temperature perovskite oxides are sufficiently active to serve as the cathode and perform the oxygen reduction reaction (ORR) . It is desirable to operate SOFCs at lower temperatures, although at lower temperatures perovskites do not have sufficient catalytic activity and produce large voltage losses, thus new catalysts are actively being sought . Recent SOFCs may produce over 1.3W/cm 2 at below 500 °C, but must use short-lived Pt catalysts to achieve such high performance .…”

Section: Introductionmentioning

confidence: 99%

Nonprecious Metal Catalysts for Low Temperature Solid Oxide Fuel Cells

Holme

Prinz

2011

J. Phys. Chem. C

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“…When the voltage became lower (0.3V), the silver oxides decomposed and provided more oxygen for the ORR. The same trend of the change of polarization resistance was reported in the earlier studies on Ag cathode 17,124 . For the porous Ag, since gaseous oxygen could directly supply to TPB, there was no increase of polarization resistance observed when the current density increased.…”

Section: Eis Analysis On Silver Cathodessupporting

confidence: 86%

Developing metallic cathode for low-temperature solid oxide fuel cell applications

Yu¹

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Solid oxide fuel cell (SOFC) is a high-efficient energy conversion device, which can transform chemical energy into electricity directly. With the effort input by numerous researchers in the past decade, the operating temperature of SOFCs had been successfully decreased to below 500 ˚C with more than 1 W•cm-2 of output power density. At low operating temperature, one of the major issues is the sluggish kinetics of oxygen reduction reaction, which causes the major loss. To achieve high performance at a low operating temperature of 300 to 500 ˚C for SOFC, this dissertation is dedicated to developing metal-based cathodes that can meet the criteria of long-term stability, low area-specific resistance, easy to fabricate, and cost effective. To study the stability of metallic cathode, an interfacial structure characterization method, double cantilever beam delamination, was developed to determine the triple phase boundary structure for the thin-film electrode. By this delamination technique, the thermal-driven morphological evolution between the electrode top surface and the substrate contact interface were compared. For the nanoporous platinum electrode, the temperature required for significant agglomeration to occur was approximately 100 °C higher at electrolyte contact interface than at the top surface. In the next stage, inkjet printing technique was employed to fabricate Ag cathode. Comparing to the conventional thin-film electrode that was fabricated by sputtering, the cathode fabricated by inkjet printing showed improved performance and structural stability. In a 45-hour test on fuel cell operation, the cell with an inkjetprinted cathode had a current output degradation of 12.1 % at 400 ˚C; while the degradation of sputtered Ag cathode was 68.1 % after a 20-hour test. For a highperformance fuel cell, a porous silver cathode is required, and this simple inkjet Abstract ii printing technique provides an effective way to achieve such desirable porous structure with required thermal morphological stability. To further enhance the stability of Ag cathode, the surface modification was employed by sputtering a 2 nm-thick of gadolinium-doped ceria (GDC) on the Ag cathode. With the GDC capping layer, the thermal stability of Ag cathode was improved. The GDC-modified cathode could be operated at 400 ˚C for 24 h with 7.8 % of output degradation. To study the effect of GDC coating on surface O-exchange properties, a "porous and dense" bi-layered Ag cathode and a "porous" Ag cathode were used for surface modification. When GDC capping was applied, the ohmic resistance reduced from 1186.0 to 1052.0 Ωcm 2 while the polarization resistance increased from 767.3 to 2541.4 Ωcm 2 at 400 ˚C for the bi-layered Ag cathode; for the porous Ag cathode, the ohmic resistance reduced from 1190.0 to 963.5 Ωcm 2 while the polarization resistance increased from 325.8 to 421.2 Ωcm 2. This GDC capping layer could reduce the ohmic resistance due to the extra ion conduction pathways, while the polarization resistance increased since the GDC cappin...

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Oxygen Reduction Characteristics on Ag, Pt, and Ag-Pt Alloys in Low-Temperature SOFCs

Cited by 25 publications

References 23 publications

Novel CO₂-tolerant ion-transporting ceramic membranes with an external short circuit for oxygen separation at intermediate temperatures

Novel CO₂-tolerant ion-transporting ceramic membranes with an external short circuit for oxygen separation at intermediate temperatures

Nonprecious Metal Catalysts for Low Temperature Solid Oxide Fuel Cells

Developing metallic cathode for low-temperature solid oxide fuel cell applications

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Oxygen Reduction Characteristics on Ag, Pt, and Ag-Pt Alloys in Low-Temperature SOFCs

Cited by 25 publications

References 23 publications

Novel CO2-tolerant ion-transporting ceramic membranes with an external short circuit for oxygen separation at intermediate temperatures

Novel CO2-tolerant ion-transporting ceramic membranes with an external short circuit for oxygen separation at intermediate temperatures

Nonprecious Metal Catalysts for Low Temperature Solid Oxide Fuel Cells

Developing metallic cathode for low-temperature solid oxide fuel cell applications

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Novel CO₂-tolerant ion-transporting ceramic membranes with an external short circuit for oxygen separation at intermediate temperatures

Novel CO₂-tolerant ion-transporting ceramic membranes with an external short circuit for oxygen separation at intermediate temperatures