Non-bonding interaction of dual atom catalysts for enhanced oxygen reduction reaction

Abstract

We demonstrate the design of graphene-supported dual atom catalysts (DACs) for the four-electron oxygen reduction reaction (ORR), by utilizing the non-bonding interaction of counterpart metals (M) that synergistically tune the electronic properties and catalytic activity of the Fe active site in FeMN₆-DAC and FeMN₈-DAC systems, where M stands for Fe, Co, Ni, Cu, and Zn. More specifically, for Fe-M distances below 15 Å, the non-bonding interaction is significant, making the system act as the DAC. We predicted that FeNiN₆-DAC and FeNiN₈-DAC exhibit a low ORR overpotential (η^(ORR)) of 0.28 V and 0.47 V, respectively, which are at the summits of volcano plots. This low η^(ORR) originates from the high Bader charge transfer coupled with high spin density at the Fe site in both the FeNiN₆-DAC and FeNiN₈-DAC systems, which weakens the adsorption of OH* intermediate while enhancing its desorption to H₂O. Guided by these density functional theory (DFT) computational results, we synthesized FeCoN₈-DAC and FeNiN₈-DAC along with N-doped graphene and confirmed their structures with scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and electron spin resonance (ESR). We verify experimentally the catalytic activities and find that FeNiN₈-DAC has the low experimental overpotential of 0.39 V with a Tafel slope of 47 mVdec⁻¹. Based on these results, we propose a DFT-guided strategy to tune the charge transfer and spin population of the active site toward designing DACs for electrochemical ORR.

Group Members

William A. Goddard III

Charles and Mary Ferkel Professor