• Energy Research

Abstract The electrode temperature distribution of a solid oxide fuel cell is an important parameter to consider for gaining better insight into the cell performance and its temperature-related degradations. The present efforts of measuring gas channel temperatures do not accurately reveal the cell surface temperature distribution. Therefore, the authors propose a cell-integrated multi-junction thermocouple array to measure the electrode temperature distribution from a working solid oxide fuel cell. In this work, the authors deposited a thin film/wire multi-channel thermal array on the cathode of a commercially-sourced solid oxide fuel cell. The temperature of the cell was measured under varying fuel compositions of hydrogen and nitrogen. The multi-channel array showed excellent temperature correlation with the fuel flow rate and with the cell’s performance whilst commercial thermocouples showed a very dull response (10 ~ 20 °C discrepancy between thermocouples and the multi-channel array). Furthermore, cell temperature measurements via the multi-channel array enabled detecting potential fuel crossover. This diagnostic approach is applied to a working solid oxide fuel cell, yielding insights into key degradation modes including gas-leakage induced temperature instability, its relation to the theoretical open circuit voltage and current output, and propagation of structural degradation. It is envisaged that the use of the multi-thermocouple array techniques could lead to significant improvements in the design of electrochemical energy devices, like fuel cells and batteries and their safety features, and other hard-to-reach devices such as inside an internal combustion engine or turbine blades.

Schematics of water-mediated ex-solution and accordingly nano-engineered protonic ceramic fuel cell furnished with the water-mediated ex-solution on a cathode and H2 ex-solution on an anode.

Combination of nanostructured ceria and nanoscale metal particles leads to unprecedented activity for hydrogen and methane electro-oxidation along with excellent morphological stability.

Tuning of the cation–oxygen bond strength effectively promotes B-site ex-solution in a perovskite, thereby boosting the catalytic activity of CO oxidation.

This review comprehensively examines recent progress, identifies critical challenges, and outlines future directions for electricity-to-NH3 interconversion in proton ceramic cells.

In the perovskite oxide BaFeO3, inducing a tensile in-plane strain or introducing a larger radius cation suppresses the surface Ba enrichment. In turn, a reduced surface Ba concentration improves the surface electrocatalytic activity.

ABSTRACTSubstituting the sluggish oxygen evolution reaction with a more thermodynamically favorable ethanol oxidation reaction (EOR) offers an opportunity to circumvent the efficiency loss in water splitting and metal‐air batteries. However, the effect of the dynamic surface evolution of the catalyst in operating conditions on the activity of EOR lacks comprehensive understanding. Herein, we demonstrate a tunable operational catalyst activity through the modulated redox property of nickel oxalate (NCO) by establishing a relation between the oxidation behavior of Ni, surface reconstruction, and catalyst activity. We propose a repeated chemical–electrochemical reaction mechanism of EOR on NCO, which is rigorously investigated through a combination of operando Raman and nuclear magnetic resonance. The modulation of the oxidation trend of Ni by doping heteroatoms stimulates the electrochemical oxidation of the catalyst surface to NiOOH, which alters the catalyst activity for EOR. Assembled ethanol‐assisted water electrolysis cell exhibits a reduced operating voltage for hydrogen production by 200 mV with a ~100% Faradaic efficiency, and zinc–ethanol–air battery showed a 287 mV decreased charge–discharge voltage window and enhanced stability for over 500 h.

The correlation between the surface chemistry and electronic structure is studied for SrTi1−xFexO3 (STF), as a model perovskite system, to explain the impact of Sr segregation on the oxygen reduction activity of cathodes in solid oxide fuel cells. Dense thin films of SrTi0.95Fe0.05O3 (STF5), SrTi0.65Fe0.35O3 (STF35) and SrFeO3 (STF100) were investigated using a coordinated combination of surface probes. Composition, chemical binding, and valence band structure analysis using angle-resolved X-ray photoelectron spectroscopy showed that Sr enrichment increases on the STF film surfaces with increasing Fe content. In situ scanning tunnelling microscopy/spectroscopy results proved the important and detrimental impact of this cation segregation on the surface electronic structure at high temperature and in an oxygen environment. While no apparent band gap was found on the STF5 surface due to defect states at 345 °C and 10−3 mbar of oxygen, the surface band gap increased with Fe content, 2.5 ± 0.5 eV for STF35 and 3.6 ± 0.6 eV for STF100, driven by a down-shift in energy of the valence band. This trend is opposite to the dependence of the bulk STF band gap on the Fe fraction, and is attributed to the formation of a Sr-rich surface phase in the form of SrOx on the basis of the measured surface band structure. The results demonstrate that Sr segregation on STF can deteriorate oxygen reduction kinetics through two mechanisms – inhibition of electron transfer from bulk STF to oxygen species adsorbing onto the surface and the smaller concentration of oxygen vacancies available on the surface for incorporating oxygen into the lattice.

While SOFC perovskite oxide cathodes have been the subject of numerous studies, the critical factors governing their kinetic behavior have remained poorly understood. This has been due to a number of factors including the morphological complexity of the electrode and the electrode- electrolyte interface as well as the evolution of the surface chemistry with varying operating conditions. In this work, the surface chemical composition of dense thin film SrTi1−xFexO3-δelectrodes, with considerably simplified and well-defined electrode geometry, was investigated by means of XPS, focusing on surface cation segregation. An appreciable degree of Sr-excess was found at the surface of STF specimens over the wide composition range studied. The detailed nature of the Sr-excess is discussed by means of depth and take-off angle dependent XPS spectra, in combination with chemical and thermal treatments. Furthermore, the degree of surface segregation was successfully controlled by etching the films, and/or preparing intentionally Sr deficient films. Electrochemical Impedance Spectroscopy studies, under circumstances where surface chemistry was controlled, were used to examine and characterize the blocking effect of Sr segregation on the surface oxygen exchange rate.