Electrochemical insights into performance enhancement of protonic ceramic fuel cells with Ba(Zr,Ce,Y)O_3-δ electrolyte

The burgeoning field of protonic ceramic fuel cells (PCFCs) is characterized by significant scientific and technological advancements, particularly with the incorporation of BaZr_0.1Ce_0.7Y_0.2O_3-δ (BZCY) as a proton-conducting electrolyte. In the modern energy materials field, the challenge is not only developing new materials but also understanding new mechanisms and gaining an in-depth understanding of their interaction with energy devices. To drive significant advances, it is crucial to address both material-specific challenges and device-level innovations that unlock the full potential of these materials. In this work, we introduced an electrochemical proton injection approach to successfully improve BZCY proton conductivity by an order of magnitude. We also delve into the electrode and interface kinetic processes and their interplay in proton transport within the bulk and grain boundary of the BZCY-electrolyte of PCFCs. These approaches have led to state-of-the-art advances, achieving a proton conductivity of 0.19 S cm⁻¹ and a device peak power density of 943 mW cm⁻² at 530 °C. Our results demonstrate that the bulk and grain boundary conduction significantly mitigate polarization losses by four to five orders of magnitude, thereby accelerating the kinetic process and further contributing to improved PCFC performance. The appearance of peaks and alterations in relaxation times further illustrate the electrode reactions and proton transport mechanisms. Beyond providing a comprehensive assessment of current technological progress, this article underscores the transformative potential of electrochemical processes in PCFCs, positioning them as a cornerstone in the quest for sustainable and clean energy technologies.