Fuel cells offer the possibility of zero-emissions electricity generation and increased energy security. We review here the current status of solid oxide (SOFC) and polymer electrolyte membrane (PEMFC) fuel cells. Such solid electrolyte systems obviate the need to contain corrosive liquids and are thus preferred by many developers over alkali, phosphoric acid or molten carbonate fuel cells. Dramatic improvements in power densities have been achieved in both SOFC and PEMFC systems through reduction of the electrolyte thickness and architectural control of the composite electrodes. Current efforts are aimed at reducing SOFC costs by lowering operating temperatures to 500–800 °C, and reducing PEMFC system complexity be developing ‘water-free’ membranes which can also be operated at temperatures slightly above 100 °C.

Fuel cell materials and components

The commercial breakthrough of solid oxide fuel cells (SOFCs) is still hampered by degradation related issues. Most SOFCs that perform well do not possess good stability. To achieve a targeted degradation rate of 0.2%/1000 h important to a durable SOFC device, it is vital to identify the sources of degradation. So far, the longest stable performance was given by F1002-97, a short stack from Forschungszentrum Jülich GmbH, which reached 93,000 h of operation at 700 °C under 0.5 A cm−2 constant current density with a degradation rate of 0.5%/1000 h. In this review, we discuss the most detrimental degradation mechanisms for the core components of the SOFC, mainly poisoning, microstructural deformations, and strains. Electrochemical, chemical, and structural characterization tools for quantifying degradation mechanisms are also presented. The following section addresses the most recent progress in SOFC durability and the associated methods for analyzing degradation. These techniques include different doping techniques (including Mo, Nb, Co, Ce, Ta, Sn, etc.), surface modifications (e.g.infiltration, exsolution techniques, protective coatings), and interface engineering. Finally, the factors that inhibit the enhancement of SOFC durability are briefly discussed, such as inadequate knowledge of the degradation process and limitations in the material choices. 

A review on solid oxide fuel cell durability: Latest progress, mechanisms, and study tools

An Efficient Bifunctional Air Electrode for Reversible Protonic Ceramic Electrochemical Cells

Nanocomposites: A New Opportunity for Developing Highly Active and Durable Bifunctional Air Electrodes for Reversible Protonic Ceramic Cells

Abstract Reversible protonic ceramic electrochemical cells (R-PCECs) are ideally suited for efficient energy storage and conversion; however, one of the limiting factors to high performance is the poor stability and insufficient electrocatalytic activity for oxygen reduction and evolution of the air electrode exposed to the high concentration of steam. Here we report our findings in enhancing the electrochemical activity and durability of a perovskite-type air electrode, Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O 3-δ (BCFN), via a water-promoted surface restructuring process. Under properly-controlled operating conditions, the BCFN electrode is naturally restructured to an Nb-rich BCFN electrode covered with Nb-deficient BCFN nanoparticles. When used as the air electrode for a fuel-electrode-supported R-PCEC, good performances are demonstrated at 650 °C, achieving a peak power density of 1.70 W cm −2 in the fuel cell mode and a current density of 2.8 A cm −2 at 1.3 V in the electrolysis mode while maintaining reasonable Faradaic efficiencies and promising durability. 

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Surface restructuring of a perovskite-type air electrode for reversible protonic ceramic electrochemical cells

Reversible protonic ceramic electrochemical cells (R-PCECs) are a promising option for efficient and low-cost generation of electricity and hydrogen Commercialization of R-PCECs, however, hinges o

An Active and Robust Air Electrode for Reversible Protonic Ceramic Electrochemical Cells

Enhancing Oxygen Reduction Activity and Cr Tolerance of Solid Oxide Fuel Cell Cathodes by a Multiphase Catalyst Coating

Solid oxide cells (SOCs) are considered the most efficient system for reversible conversion between chemical and electrical energy, thus having potential to be an attractive technology for a sustainable energy future. To achieve high round-trip efficiency, highly efficient and durable air electrode materials are needed to minimize energy loss associated with oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Here we report a bi-functional air electrode material, PrBa0.9Co1.96Nb0.04O5+δ, demonstrating outstanding electrochemical performance (e.g., achieving peak power densities of over 1.5 and 1 W cm−2, respectively, for Gd0.1Ce0.9O1.95 and BaZr0.1Ce0.7Y0.1Yb0.1O3-δ based fuel cells at 600 °C) while maintaining excellent stability (e.g., having a degradation rate of 40 mV per 1,000 h for H2O electrolysis cells). The excellent property of the new electrode is attributed to the improved stability from Nb doping and the enhanced electrocatalytic activity from tuning Ba deficiency, as confirmed by experimental results and computational analysis.

A highly efficient and durable air electrode for intermediate-temperature reversible solid oxide cells

Solid oxide fuel cells (SOFCs) are a promising solution to a sustainable energy future. However, cell performance and stability remain a challenge. Durable, nanostructured electrodes fabricated via a simple, cost-effective method are an effective way to address these problems. In this work, both the nanostructured PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF) cathode and Ni-Ce0.8Sm0.2O1.9 (SDC) anode are fabricated on a porous yttria-stabilized zirconia (YSZ) backbone via solution infiltration. Symmetrical cells with a configuration of PBSCF|YSZ|PBSCF show a low interfacial polarization resistance of 0.03 Ω cm2 with minimal degradation at 700 °C for 600 h. Ni-SDC|YSZ|PBSCF single cells exhibit a peak power density of 0.62 W cm-2 at 650 °C operated on H2 with good thermal cycling stability for 110 h. Single cells also show excellent coking tolerance with stable operation on CH4 for over 120 h. This work offers a promising pathway toward the development of high-performance and durable SOFCs to be powered by natural gas.

Yinghua Niu

Papers

An Active and Robust Air Electrode for Reversible Protonic Ceramic Electrochemical Cells

Enhancing Oxygen Reduction Activity and Cr Tolerance of Solid Oxide Fuel Cell Cathodes by a Multiphase Catalyst Coating

A highly efficient and durable air electrode for intermediate-temperature reversible solid oxide cells

High-Performance, Thermal Cycling Stable, Coking-Tolerant Solid Oxide Fuel Cells with Nanostructured Electrodes.