Electrochemical Impedance Analysis of Symmetrical Ni/Gadolinium-Doped Ceria (CGO10) Electrodes in Electrolyte-Supported Solid Oxide Cells

One of the most powerful tools in solid oxide cell (SOC) characterization is electrochemical impedance spectroscopy, which can unfold important insights into SOC performance characteristics and degradation behavior. To obtain a better understanding of the electrochemical behavior of Ni/CGO fuel electrodes, this work presents a comprehensive investigation of state-of-the-art Ni/CGO10- based electrolyte-supported cells. Commercial Ni/CGO10|CGO10|3YSZ|CGO10|Ni/CGO10 symmetrical cells were characterized between 550–975°C at pH2 = 0.8 bar and pH2O = 0.2 bar, and for different H2/H2O gas mixtures at 550°C. (i) Small electrode area, (ii) thin electrodes and (iii) large gas flow rates were used to minimize mass transport contributions. Based on distribution of relaxation times (DRT) analysis an equivalent circuit model was derived. Electrode process contributions on Ni/CGO were determined by means of a complex non-linear least square fit of the equivalent circuit model to the experimental data. One low frequency process at 0.1–1 Hz and one middle frequency process at 10–100 Hz were identified and correlated to a surface and a bulk process, respectively. Values for the apparent activation energy barriers and reaction orders with respect to steam and hydrogen content were determine

Performance and Limitations of Nickel-Doped Chromite Anodes in Electrolyte-Supported Solid Oxide Fuel Cells

Ni-doped chromite anodes were integrated into electrolyte-supported cells (ESC) with 5x5 cm2 size and investigated in fuel cell mode with H2/H2O fuel gas. Both a stoichiometric and a nominally A-site deficient chromite anode material showed promising performance at 860 °C approaching the ones of state-of-the-art Ni/Gd-doped ceria (CGO) anodes. While the difference in polarization resistance was small, an increased ohmic resistance of the perovskite anodes was observed, which is related to limited electronic conductivity of the perovskites. Increasing the chromite electrode thickness was shown to enhance performance and stability considerably. Degradation increased with current density, suggesting its dependency on the electrode potential, and could be reversed by redox cycling. Sulfur poisoning with 20 ppm hydrogen sulfide led to rapid voltage drops for the chromite anodes. It is discussed that Ni nanoparticle exsolution facilitates hydrogen dissociation to the extent that it is not rate-limiting at the investigated temperature unless an insufficiently thick electrode thickness is employed or sulfur impurities are present in the feed gas

Metal Supported Proton Conducting Ceramic Cell with Thin Film Electrolyte for Electrolysis Application

Manufacturing of metal supported proton conducting ceramic cells is investigated in the present study. A low temperature fabrication route was chosen to avoid metal corrosion during the fabrication process, in which pulsed laser deposition (PLD) was employed to apply the thin-film BaZr0.7Ce0.2Y0.1O3-δ electrolyte layer. The surface condition of the support layer is a critical aspect to produce a dense and gas-tight electrolyte layer by PLD. In order to decrease the average size of the 10-30 µm large pores in metal substrate down to the nano-scale, different powders with different particles size were successfully fabricated and integrated into a pore-size graded structure to form a homogeneous porous surface whose size distribution meets the requirements for making a dense PLD coating layer. An electrolyte layer with the intended phase is achieved with a thickness of around 1 µm. Initial electrochemical investigation with a Pt oxygen electrode showed a total resistance of 4.92 Ω cm2 at 600 °C at OCV

Progress and Prospects in the Development of Metal Supported Proton Conducting Ceramics for Steam Electrolysis and Other Electrochemical Energy Conversion Devices

Technological development of proton conducting ceramic cell (PCC) manufacturing is in progress. Both high electrochemical performance and robustness in long term operation are crucial for practical devices. The metal-supported (MS) architecture is one of the promising alternatives to the state-of-the-art ceramic supported SOCs, due to its high tolerance towards thermal/redox cycling that are key features for flexible and reliable operation in high temperature fuel cell and electrolysis applications. Relying on the perovskite-type PCC electrolyte, whose refractory nature requires high sintering temperatures in the conventional chemical processing route, the challenge in MS-PCC manufacturing is to achieve a gas-tight electrolyte layer without degradation of the metal substrate. Our strategy is the multilayer implementation combining wet chemical processing of the functional fuel electrode in air below 1000°C and Physical Vapor Deposition (PVD) techniques below 800 °C for the gas-tight electrolyte coating. PCCs are suitable for MS architecture, that can provide potentially high performances and high mechanical stability for a wide range of electrochemical applications. We are working on the MS-PCC development in different projects. In the project DAICHI (EIG CONCERT-Japan, BMBF/01DR18002), we started with Pulsed Laser Deposition (PLD) to manufacture the gas tight electrolyte layer and obtained the first working MS-PCC in steam electrolysis application [1]. The concept is transferred to scalable techniques in projects ARCADE (BMBF/03SF0580A) and 112CO2 (Horizon 2020/952219). We will present our progress in the development of MS-PCC and discuss on the prospects to manufacture large-scale robust PCC cells at reasonable costs for different electrochemical applications. [1] Haoyu Zheng, Feng Han, Noriko Sata, Matthias Riegraf, Amir Masoud Dayaghi, Truls Norby, Rémi Costa, Metal Supported Proton Conducting Ceramic Cell with Thin Film Electrolyte for Electrolysis Application, ECS Transactions, 103 (1), 693-700 (2021