Confinement engineering for enhanced electrocatalytic nitrate reduction by integrating B-doped graphene with iron catalysts for long-term stability

Abstract

Electrocatalytic nitrate reduction (NO₃RR) is considered an economical and effective method for the removal of N-containing pollutants, and Fe-based catalysts show great potential for numerous electrocatalytic applications. However, for most Fe-based NO₃RR electrocatalysts developed to date, achieving an optimized tradeoff between activity and stability has been challenging owing to excessive agglomeration and shedding of Fe nanoparticles. Herein, we report that Fe nanoparticles confined with B-doped graphene nano-chainmail (Fe@B-Gnc) exhibit electrocatalytic NO₃RR to N₂ with nearly 100% selectivity and 75.2% NO₃⁻ conversion within 12 h, as well as excellent long-term cycle stability (30 cycles, 12 h per cycle). This outstanding performance is associated with the B-doped graphene nano-chainmail, which confines the agglomeration of Fe nanoparticles at high temperatures and engenders a strong protective layer for the encapsulated Fe nanoparticles, enabling Fe@B-Gnc to maintain its long-term electrocatalytic NO₃RR activity. Additionally, the difference in electronegativity between B and C atoms renders the local electron-deficient environment at the B-doped site favorable for NO₃⁻ adsorption and accelerates electron transfer and distribution at the Fe–C interface, further improving the reaction rate of electrocatalytic NO₃RR. This work sheds light on Fe-based catalysts for a wide range of electrocatalytic NO₃RR applications, providing a potential countermeasure to aid in balancing the global nitrogen cycle.