Synergistic curvature and heteroatom-doping effects in C₆₀ for efficient electrochemical urea synthesis

Abstract

The energy-intensive and environmentally detrimental Haber-Bosch process for urea production underscores the critical need for sustainable alternatives. Electrochemical C–N coupling from CO2₂ and nitrate (NO3—) offers a promising green synthesis route. Herein, we report a systematic density functional theory (DFT) investigation of heteroatom-doped C60 fullerenes (C59X, X = B, N, P, O, S) as electrocatalysts for urea synthesis. Among these, C59N emerges as a superior metal-free catalyst, exhibiting exceptional stability and activity. Its synergistic combination of inherent curvature and nitrogen doping enhances adsorption of key intermediates (*NO and *CO), enabling sequential C–N coupling with remarkably low kinetic barriers (0.53 eV and 0.42 eV). The curved, N-doped framework further stabilizes critical reaction intermediates (*ONCO and *ONCONO), ensuring efficient pathway progression. Hydrogenation to form *NCONH is identified as the rate-limiting step, requiring a modest limiting potential of −0.54 V—competitive with state-of-the-art metal catalysts while suppressing parasitic reactions**. This work establishes C59N as a high-performance, metal-free electrocatalyst for urea synthesis and provides fundamental design principles (curvature-induced bond activation + heteroatom-tuned electronic modulation) for next-generation sustainable nitrogen fixation and carbon utilization technologies.