Atomically dispersed Fe-Cu dual-site catalysts synergistically boosting oxygen reduction for hydrogen fuel cells

Abstract

Compared to most popular single-atom catalysts (SACs), the dual-atom catalysts may possess better catalytic performance due to the synergistic effect of dual-atom sites. However, revealing the synergistic mechanism of dual-atom sites to improve catalytic activity is still insufficient. Here, atomically dispersed FeCu-NC catalyst containing FeN4 and CuN4 dual active sites is synthesized, and has been identified by high angle annular dark-field STEM and X-ray absorption spectroscopy. The as-synthesized FeCu-NC exhibits a half-wave potential of 0.882 V, which is nearly 40 mV superior to Pt/C catalyst and 24 mV better than Fe-NC SAC in alkaline medium. Using FeCu-NC as a cathode catalyst, the assembled hydroxide exchange membrane fuel cell presents a peak power density of 0.91 W·cm−2, which is ∼ 21% higher than of Fe-NC based one (0.76 W·cm−2). DFT calculations reveal that the strain effect caused by the CuN4 species replacing the neighbor carbon environment of the FeN4 species, can efficiently tailor the electronic structure and reduce the OH* adsorption on FeN4 species and therefore improves the catalytic activity and kinetic process of ORR. This work provides a new insight into the synergistic catalysis of dual-atom sites for ORR.