Guanine-derived F, N co-doped carbon-shell encapsulated iron carbide nanoparticles for enhanced CO₂ electroreduction activity

The development of highly selective, cost-effective, and energy-efficient electrocatalysts is critical for carbon dioxide reduction reaction (CO₂RR) to produce high-value products. Herein, we propose a facile strategy to obtain F, N co-doped carbon-coated iron carbide (Fe₃C) nanoparticles by using biomolecule guanine and hexadecafluorophthalocyanine iron as raw materials. Remarkably, this method involves only one-step pyrolysis and does not require any guiding agent or sacrificial template. Benefiting from the advantageous surface microenvironment adjustments achieved through graphitic N (G_N) and F co-doping, Fe₃C@NF-G-1000 demonstrates exceptional efficacy in the electroreduction of CO₂ to carbon monoxide (CO) with an impressive Faradic efficiency (FE_co) up to 98% at the potential of −0.55 V (vs. reversible hydrogen electrode (RHE)). Furthermore, it delivers a remarkable current density of up to −43 mA·cm⁻² and exhibits virtually no current attenuation over a span of 20 h within the flow cell. Insights from density functional theory (DFT) calculations reveal that the composite structure of G_N and F co-doped graphitic layer and Fe₃C exhibits different electron density distributions from that of iron carbide nanoparticles. This is attributed to the synergistic effect of the composite structure leading to the enrichment of electrons in the graphite layer on the surface, which contributes to the stability of the key reaction intermediate *COOH, thus, resulting in an enhanced catalytic activity and efficiency. Overall, this work introduces a new and promising approach to the design of green and low-cost carbon-coated metal materials for CO₂ reduction reactions.