Fe nanoparticles embedded in N-doped porous carbon for enhanced electrocatalytic CO2 reduction and Zn-CO2 battery

The selective electrochemical reduction of CO2 to CO is a promising solution for the design of carbon-neutral, sustainable processes. Achieving a highly selective single reduction product is still challenging because of the energetically favorable competing hydrogen evolution reaction. We report the fabrication of N-doped sponge-like porous graphitic carbon structures embedded with Fe nanoparticles (Fe@NPC) via the pre-modification of a metal-organic framework (IRMOF-3(Zn)) with carboxyferrocene, followed by pyrolysis. The as-prepared Fe@NPC exhibited a 96.4% CO Faradaic efficiency at -0.5 VRHE and good stability. The exceptional CO2 reduction performance is attributed to the unique structure of the composite catalyst, which provides abundant hierarchical pores that increase CO2 adsorption and mass transfer, and active Fe sites that synergistically accelerate the kinetics of CO generation. The in situ attenuated total reflectance-Fourier transform infrared analysis provided proof of the improved ability of Fe@NPC to accumulate the crucial intermediate *COOH compared with other pyrolyzed porous carbons. Fe@NPC was used in a Zn-CO2 battery that delivered a maximum power density of 3.0 mW cm-2, evidencing its potential for application in energy-converting devices. Published by Elsevier B.V. All rights reserved.

Automated summary

Selective electrochemical reduction of CO2 to CO remains challenging due to the competing hydrogen evolution reaction. In this study, N-doped sponge-like porous graphitic carbon structures embedded with Fe nanoparticles (Fe@NPC) were fabricated and showed a high CO Faradaic efficiency of 96.4% and good stability. This outstanding CO2 reduction performance was attributed to the unique structure of Fe@NPC, which provided abundant hierarchical pores for CO2 adsorption and mass transfer, as well as active Fe sites that accelerated CO generation kinetics. Fe@NPC also exhibited improved ability to accumulate the crucial intermediate *COOH compared to other pyrolyzed porous carbons. Fe@NPC was further utilized in a Zn-CO2 battery, demonstrating its potential for energy-converting devices.