Experimental and DFT studies of oxygen reduction reaction promoted by binary site Fe/Co–N–C catalyst in acid

The cost and efficiency issues of cathodic electrocatalyst for oxygen reduction reaction (ORR) hinder a broad application of fuel cells. Therefore, it is necessary to develop highly efficient and sustainable ORR electrocatalysts of platinum group metal-free (PGM-free). The atomically dispersed FeCoNC-10 electrocatalysts were constructed by incorporating Fe phthalocyanine (FePc) molecules into bimetallic metal–organic frameworks (BMOF) followed by one-step pyrolysis. It showed remarkable ORR activity in acidic medium compared with FeNC and CoNC catalysts. The Fe–Co bimetallic sites were confirmed in FeCo–N–C, together with abundant isolated FeN4 and CoN4 sites. Theoretical study revealed that the bimetallic site can enhance O2 adsorption and elongate O–O bond length rather than FeN4 and CoN4. This can result in facile cleavage of the O–O bond and thus a direct 4e− ORR process. FeCoNC-10 catalyst showed enhanced ORR stability, due to very weak Fenton-type reaction related to Co species. Membrane electrode assemblies (MEAs) consisted of the FeCoNC-10 was applied in the cathode. It showed a peak power density of 100 mW cm−2 in a direct methanol fuel cells (DMFCs) with superior methanol tolerance. This work sheds light on the mechanism of atomically dispersed Fe/Co dual-doped carbon in enhancing ORR activity and stability, which enables the cost-effective ORR electrocatalyst design to achieve robust fuel cell performance.