Cu and Fe dual-atom nanozyme mimicking cytochrome c oxidase to boost the oxygen reduction reaction

The intrinsically sluggish kinetics of oxygen reduction reaction (ORR) and overuse of expensive and unstable Pt-based catalysts have severely hampered the development of clean energy technologies. Herein, a type of non-noble metal nanozyme as ORR electrocatalyst, with Fe-Cu dual atomic sites embedded in three-dimensional porous N-doped carbon (FeCu-DA/NC), is fabricated by mimicking both the constituents of active centers and enzymatic microenvironment of Cytochrome c oxidase (CcO). The atomically dispersed Fe-Cu single atom sites are clearly identified by direct aberration-corrected transmission electron microscopy imaging, systematic X-ray absorption fine structure (XAFS) analyses, and density functional theory (DFT) calculations. The FeCu-DA/NC exhibits a superior ORR activity, with about 30 mV more positive half-wave potential (E1/2) than that of commercial Pt/C catalyst in base, and moreover with only an E1/2 gap of 20 mV to the Pt/C in acid. Importantly, the FeCu-DA/NC displays an excellent durability in both acid and base conditions, which is much superior to Pt/C. DFT calculations further demonstrate that the enhanced performance can be attributed to the unique synergistic effect between Cu and Fe single atoms in which Cu-N4 serves as the electron donor to increase the electron density of the active centers of Fe-N4 and thus to facilitate O2 activation.