Polarisation mechanism of the misfit Ca-cobaltite electrode for reversible solid oxide cells

Analysis of La4Ni3O10±δ-BaCe0.9Y0.1O3-δ Composite Cathodes for Proton Ceramic Fuel Cells

“…Nonetheless, several drawbacks remain when working at such low temperatures, with the minimisation of polarisation resistance being one of the most critical challenges remaining to date [4,5]. In this respect, the majority of published works have focused on the use of mixed ionic electronic conductors (MIECs) as potential PCFC electrodes, where materials selection is driven by that traditionally used in solid oxide fuel cells (SOFCs), based on both oxide-ion and electron (O 2− /e − ) conduction [6][7][8][9][10][11][12]. One good example is that of the layered Ruddlesden-Popper (RP) lanthanide nickelates, Ln n+1 Ni n O 3n+1 (Ln = La, Pr, and Nd; n = 1, 2, and 3) [13][14][15][16].…”

“…Of concern, this factor may become relevant upon applied cathodic polarisation due to a localised drop in the chemical potential of oxygen at the cathode/electrolyte interface upon fuel cell operation [7,22]. Nonetheless, reference to Figure 1 shows that this pO2 decomposition limit can be improved upon decreasing the operation temperature to the intermediate range (i.e., below 600 °C), an operating window that concurs well with the temperature range of interest for PCFCs (400-600 °C).…”

Boosted electrochemical performance of ca‐cobaltite‐based composite electrodes for reversible solid oxide cells

“…The superior performance under anodic polarisation was previously associated with the fact that the OER is limited only by bulk/surface diffusion of oxygen species, as neither electron transfer nor oxygen desorption is expected to be rate-limiting. 3,14 In this respect, anodic polarisation may benefit the diffusion processes in the C349 material, which may occur in both bulk and/or surface regions. 35,36 The addition of CGO20 substantially enhances the triple-phase boundaries (TPBs) and the electrode catalytic activity for both the ORR and OER.…”

“…Regarding the development of alternative oxygen electrodes for r‐SOCs, the misfit‐layered calcium cobaltite [Ca 2 CoO 3− δ ] 0.62 [CoO 2 ] (or more commonly Ca 3 Co 4 O 9+ δ , C349) has received special attention, given its similar thermal expansion coefficient (TEC, 9‐10 × 10 −6 °C −1 , at 150°C‐820°C 10 ) to that of the Gd‐doped ceria electrolyte (10‐12 × 10 −6 °C −1 , at 30‐1000°C 11 ) and highly favourable surface‐exchange kinetics 10,12,13 . In our previous work, 14 C349 also exhibited better performance in the electrolysis mode. Nevertheless, there are few reports in the literature on this material for use in SOECs 14‐16 .…”

“…I G U R E 5 Polarisaton resistance as a function of the applied potential in cathodic polarisation A,B and anodic polarisation C,D for C349 A,C and C349/CGO20 B,D. Note that under cathodic polarisation, a maximum applied potential of À200 mV is utilised at 700 C as higher values are in the vicinity of the predicted stability limit of the misfit [Ca 2 CoO 3Àδ ] 0.62 [CoO 2 ]14 …”