A DFT Study on the Activity Origin of Fe−N−C Sites for Oxygen Reduction Reaction. Issue 15 (7th June 2022)

• Record Type: Journal Article
• Authors: Zhang, Shishi; Qin, Yanyang; Ding, Shujiang; Su, Yaqiong
• Is Part Of: Chemphyschem. Volume 23:Issue 15(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-06-07
• Subjects: active site -- density functional calculations -- electrochemistry -- oxygen reduction reaction -- single atom catalysts; Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.202200165
• Languages: English
• ISSNs: 1439-4235

Abstract

Abstract: Iron‐nitrogen‐carbon materials have been known as the most promising non‐noble metal catalyst for proton‐exchange membrane fuel cells (PEMFCs), but the genuine active sites for oxygen reduction reaction (ORR) are still arguable. Herein, by the thorough density functional theory investigations, we unravel that the planar Fe2 N6 site exhibits excellent ORR catalytic activity over both FeN3 and FeN4 sites, and the potential‐determining step is determined to be the *OH hydrogenation step with an overpotential of 0.415 V. The ORR activity of Fe2 N6 site originates from the low spin magnetic moment (1.11 μB ), which leads to high antibonding states and low d‐band center of the Fe center, further leads to weak binding strength of *OH species. The density of FeN4 sites only has little influence on the ORR activity owing to the similar interaction between active site and intermediates in ORR. Our research sheds light on the activity origin of iron‐nitrogen‐carbon materials for ORR. Abstract : The activity origin of Fe2 N6 dual‐sites for oxygen reduction reaction (ORR) was studied by DFT calculations. Comparing with FeN4 and FeN3 single‐site electrocatalysts, Fe2 N6 exhibits lower overpotentials due to its weaker adsorption for OH and lower spin magnetic moment. A linear relation between the OH adsorption energy and the overpotentials is established, so that OH could be a descriptor for ORR activity.