Enhancing protonic ceramic fuel cell performance through nanomilling of BCZY electrolyte powder

To obtain dense, high-quality electrolytes, sintering of the proton-conducting electrolyte BaCe_0.6Zr_0.2Y_0.2O₃ (BCZY) in protonic ceramic fuel cells (PCFCs) should be conducted at relatively high temperatures. However, in the co-sintering of a porous anode substrate and electrolyte thin film, high sintering temperatures often cause the coarsening of the NiO-BCZY anode, thus reducing the number of electrocatalytic active sites for H₂ oxidation as well as degrading cell performance. A scalable nanomilling process is proposed to reduce electrolyte sintering temperature to maintain triple phase boundary, good electron and proton transport in PCFC anode. By using the nanomilling process, BCZY nanoparticles more than halved the original diameter (from 297 nm to 131 nm) were produced. The co-sintering temperature can be lowered. The cell sintered at 1400 °C exhibited the highest peak power density of 490 mW/cm², 38% higher than that of un-nanomilled process. The substantial improvement in cell performance can be attributed to the lower co-sintering temperature, which caused less coarsening of the NiO anode. This preserved a greater number of electrocatalytic active sites for H₂ oxidation by Ni in cell operation, as evidenced by the 50% decrease in charge transfer resistance from electrochemical impedance measurements.