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

Abstract

The intrinsically sluggish kinetics of the 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 an 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. FeCu-DA/NC exhibits a superior ORR activity, with about 30 mV more positive half-wave potential (E_1/2) than that of commercial Pt/C catalysts in a base, and moreover with only an E_1/2 gap of 20 mV to Pt/C in an acid. Importantly, FeCu-DA/NC displays an excellent durability under both acidic and basic conditions, which is much superior to that of 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.