A-site deficient lanthanum strontium chromite perovskite La0.65Sr0.3Cr0.85Ni0.15O3-δ (L65SCrN) decorated by in situ exsolution of Ni nanoparticles was synthesized and implemented as fuel electrode on a 5 cm x 5 cm...
Ni-doped chromite anodes were integrated into electrolytesupported cells (ESC) with 5 × 5 cm 2 size and investigated in fuel cell mode with H 2 /H 2 O 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 their limited electronic conductivity. Increasing the chromite electrode thickness was shown to enhance perform-ance 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.
The lanthanum strontium chromite perovskite La 0.65 Sr 0.3 Cr 0.85 Ni 0.15 O 3-δ (L65SCrN) was implemented as fuel electrode in electrolyte-supported cells (ESC). The electrochemical cell performance in steam electrolysis operation with a fuel gas mixture of 80% H 2 O−20% H 2 was demonstrated to be comparable to that of Ni-CGO-based state of the art cells at 860 °C. At 830, 800, and 770 °C, the perovskite fuel electrode exhibited a gain in performance. Lower apparent activation energy barrier values were calculated for the L65SCrN in symmetrical and full cell configurations, in contrast to Ni-CGO fuel electrodes. A reaction model is proposed, where the water-splitting reaction mainly occurs on the oxygen vacancy sites on the L65SCrN surface and where the exsolved metallic Ni nanoparticles assist the catalytic activity of the electrode with hydrogen spillover and H 2 desorption. We observed a voltage degradation of ∼48 mV/kh during 1000 h of operation under steam electrolysis conditions at 860 °C close to the thermoneutral voltage. van der Pauw conductivity measurements corroborated this degradation with a decrease of the perovskite's p-type conductivity, which appeared to be a diffusion-limited phenomenon. Nevertheless, the lower activation energy of the perovskite-based fuel electrode for solid oxide cells (SOCs) is promising for green hydrogen production via steam electrolysis at a reduced temperature (below 860 °C) and without the need of a hydrogen sweep.
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