Current Solid Oxide cells (SOC) shows limited stability and lifetime considering the high working temperature 800-1000°C. One solution is to lower the working temperature allowing a larger range of usable material and better stability. However, reaction kinetics at the electrodes are sluggish at lower temperatures, which limits the cell performance. Then, one critical goal is to better understand the reaction pathways controlling the electrode kinetics, to be able to improve them. In the literature [1], it was shown for oxygen electrode that reaction kinetics at the electrode surface is directly dependent to the electrons availability at the surface, as well as the oxide ion conductivity of the electrode materials.

It was deduced that conduction properties of the electrode material had a direct impact on reaction kinetics and could be limited by oxygen reduction and O^2- diffusion through the bulk. It was also shown that surface chemistry has a dramatic influence on oxygen reduction. Indeed, impurities at the surface of a mixed conductor can modify reaction kinetics by many orders of magnitude. In previous works, it was demonstrated that the effect of impurities on oxygen surface exchange kinetics scales with their acidity, determined with the Smith acidity scale [2,3]. Such effect has been shown to hold for various mixed conducting oxides used as oxygen electrodes [4,5], but there is no evidence that it can be applied to other catalyzed reaction, such as the H₂O/H₂ reaction at the fuel electrode.

In this work, we studied the influence of acidic/basic oxide impurities on reaction kinetics of fuel electrodes, and whether the trends observed on air electrodes can be extended to other gas-oxides reactions. The selected anode material is Gd_0.10Ce_0.90O_1.95 as it has been proven to be an efficient standalone anode material [6]. Gd_0.10Ce_0.90O_1.95 electrodes were prepared by screen‑printing on YSZ electrolytes, and the reactions kinetics were measured by impedance spectroscopy. Then, impurities were added in-situ by infiltration of nitrate solution followed by a calcination prior to impedance measurements. The variation of reaction kinetics are discussed with respect to the Smith acidity of the impurities, their loading, and their influence on the electronic structure of the surfaces of Gd_0.10Ce_0.90O_1.95 anodes. Then, a more general discussion is proposed to compare those results with those obtained previously on cathode materials.