Surface immobilization of nitrogen-coordinated iron atoms: a facile and efficient strategy toward MNC sites with superior catalytic activities

Abstract

Atomically dispersed metal catalysts have high metal atom utilization and catalytic activity. However, the rational design and large-scale preparation of such catalysts, particularly with high metal content, remains a big challenge due to the generally used high-temperature pyrolysis. Herein, we illustrate a two-step solution: at first, an iron precursor complex was spatially confined in a porous metal–organic framework, Co(BTB); In the second, the precursor complex was immobilized on the surface under 300 °C. Owing to the high surface area and large-sized channels of Co(BTB), comprehensive characterization revealed that the immobilized iron sites were atomically dispersed on the surface even with very high metal content. The catalyst exhibited tunable and extraordinary catalytic performance in oxygen evolution reactions (OERs). With an Fe content of 4.1 wt%, an overpotential of 261 mV and unprecedented Tafel slope of 27 mV dec⁻¹ were observed, which could be attributed to the fully exposed iron sites on the surface. This fabrication method was performed at a relatively low temperature with quantitative yield, providing a facile approach for the rational design of a high-performance, stable, yet atomically dispersed metal–nitrogen–carbon electrocatalyst with tunable metal content.