Bimetal phthalocyanines and pre-treated ZIF@CNT-derived oxygen reduction reaction electrocatalysts for anion-exchange membrane fuel cells

This work presents a sophisticated two-step approach to design efficient platinum-free oxygen reduction reaction (ORR) electrocatalysts for anion-exchange membrane fuel cells (AEMFC). The anchoring of bimetal phthalocyanines (M = Fe, Co, Mn) on pre-activated zeolitic imidazolate framework (ZIF)-8 and carbon nanotube-derived carbon scaffold offered excellent active-site utilization efficiency. Raman spectroscopy revealed a highly graphitised carbon scaffold with few structural defects. The optimized FeMn-NC900a, FeCo-NC900a, and CoMn-NC900a catalysts exhibited superior ORR half-wave potential values of 0.86, 0.88, and 0.85 V, respectively, surpassing commercial Pt/C catalyst in alkaline media. These catalysts showed excellent stability over 5000 potential cycles. The electrochemical impedance spectroscopy and Tafel analysis confirmed enhanced ORR kinetics. The AEMFC achieved a peak power density of 1.02, 0.78, 0.93, and 0.56 W cm −2 with FeCo-NC900a, FeMn-NC900a, CoMn-NC900a and Pt/C catalysts, respectively. These findings underscore the engineered structural features of the pre-treated ZIF-8@CNT scaffold, which enhanced active-site density and their utilisation efficiency.