Pore surface engineering of FeNC for outstanding power density of alkaline hydrazine fuel cells

In alkaline hydrazine fuel cells (AHFCs), the rapid kinetics of hydrazine oxidation contribute to their superior power density compared to other liquid fuel cells. However, the optimization of oxygen reduction reaction (ORR) electrodes in AHFCs has received limited attention, despite the potential importance of ORR as a rate determining step. The wettability and pore structure of ORR catalysts are critical factors in facilitating reactant supply (O2 and H2O) and improving catalyst utilization. In this study, we synthesized a hierarchical pore structure in a FeNC catalyst by excess iron incorporation and steam activation, and adjusted its water/oxygen gas contact property by oxalic acid treatment. The modified catalyst exhibited improved wettability and optimized triple-phase boundaries. Remarkably, utilizing a 25 cm2 electrode size and non-noble electrocatalysts, the resulting AHFC achieved a significant power density improvement from 630 to 1240 mW cm-2, setting a new record for AHFCs. This research highlights the importance of pore structure and surface engineering, including the role of excess iron, in enhancing the performance of ORR electrodes in AHFCs.