Interpenetration twin morphology Fe-N-C as highly efficient oxygen reduction electrocatalysts for coulomb electrolytic oxygen sensor

The advancement of high-performance oxygen reduction reaction (ORR) catalysts is increasingly responsible for energy development. Iron and nitrogen co-doped carbon materials (Fe-N-C) have garnered extensive attention because of their catalytic activity, which is comparable to that of precious metal-containing catalysts. Nevertheless, the precursor ZIF-8 inevitably forms clusters during the conventional pyrolysis preparation procedure, leading to the coverage of Fe-N active sites and inhibiting catalytic performance. In this study, we induced ZIF-8 to deform into a unique interpenetration twin structure (ZIF-8-IT) by introducing the surfactant cetyltrimethylammonium bromide (CTAB), it has a concave-convex morphology with abundant facets that enhanced interfacial contactability, thereby reducing particle-to-particle interactions and alleviating agglomeration during pyrolysis. The Fe-N-C-IT catalyst prepared using ZIF-8-IT as a precursor exhibited exceptional ORR performance in alkaline media (E 1/2  = 0.898 V, E 0  = 0.983 V). Furthermore, the Fe-N-C-IT based coulomb electrolytic oxygen sensor demonstrated superior performance compared to Pt/C, it achieved an average response time of 66 s within the 100–1000 ppm oxygen concentration range, with only a 4.9 % current fluctuation observed after 28 days at a concentration of 500 ppm oxygen. This study presents a novel strategy for developing efficient oxygen reduction electrocatalysts through morphology engineering.