Electrochemical analysis of high performance protonic ceramic fuel cells based on a columnar structured thin electrolyte
Abstract High performance and cost effective fabrications should be simultaneously achieved for practical applications of fuel cells. Unfortunately, protonic ceramic fuel cells, which are considered next generation solid oxide fuel cells operating at lower temperatures =600 degC) do not satisfy the requirements. While thin electrolyte and rapid reactions at electrode/electrolyte interfaces are crucial for cell performance, the thickness of the electrolyte via cost effective ceramic processes is still not satisfactory (currently capable of >10 mm) and the electrode reaction(s) are yet to be clarified. Here we demonstrate the fabrication of a columnar structured thin electrolyte ~2.5 mm) of BaCe0.55Zr0.3Y0.15O3 d, in which no perpendicular grain boundaries exist against the current direction, through a low cost screen printing method. A high open cell voltage of 1.10 V ensures that the thin electrolyte is sufficiently dense for gas tightness, thereby achieving an extraordinary maximum power density of 350 mW/cm2 at 500 degC. The electrode reactions are investigated by distribution of relaxation time method based on electrochemical impedance spectroscopy as a function of oxygen partial pressure and hydrogen partial pressure at 500 degC, suggesting that the reaction step corresponding to the surface diffusion of an adsorbed oxygen to the triple phase boundaries at the cathode is most probably the main contributor to the overall polarization resistances.