Boosting Oxygen Reduction of Single Iron Active Sites via Geometric and Electronic Engineering: Nitrogen and Phosphorus Dual Coordination

TLDR

Atomically dispersed transition metal sites are promising catalysts and model systems, yet their preparation and characterization remain difficult, especially when engineering heteroatom‑coordinated M–N–C structures with elements such as P and S. The study aims to develop carbon nanosheets embedding nitrogen and phosphorus dual‑coordinated iron sites (Fe‑N/P‑C). These Fe‑N/P‑C nanosheets were characterized using advanced spectroscopic and microscopic techniques to confirm the dual coordination. Experimental and theoretical evidence shows that the N and P dual‑coordinated iron sites enhance oxygen intermediate adsorption/desorption, accelerating reaction kinetics and delivering promising oxygen‑reduction activity, while also offering an efficient route to prepare well‑defined single‑atom catalysts and guiding future dual‑coordination designs.

Abstract

Atomically dispersed transition metal active sites have emerged as one of the most important fields of study because they display promising performance in catalysis and have the potential to serve as ideal models for fundamental understanding. However, both the preparation and determination of such active sites remain a challenge. The structural engineering of carbon- and nitrogen-coordinated metal sites (M–N–C, M = Fe, Co, Ni, Mn, Cu, etc.) via employing new heteroatoms, e.g., P and S, remains challenging. In this study, carbon nanosheets embedded with nitrogen and phosphorus dual-coordinated iron active sites (denoted as Fe-N/P-C) were developed and determined using cutting edge techniques. Both experimental and theoretical results suggested that the N and P dual-coordinated iron sites were favorable for oxygen intermediate adsorption/desorption, resulting in accelerated reaction kinetics and promising catalytic oxygen reduction activity. This work not only provides efficient way to prepare well-defined single-atom active sites to boost catalytic performance but also paves the way to identify the dual-coordinated single metal atom sites.