Co nanoparticles on B, N–Co-doped sp2/sp3 carbon: a synergistic catalyst design for sustainable ammonia production from nitrate

Abstract

To overcome conventional carbon catalysts' trade-offs in active site density, charge transfer efficiency, and structural stability, we develop a triple-synergy strategy integrating Co-catalyzed graphitization, B–N co-doping, and small Co nanoparticle immobilization. Leveraging the N-rich framework of chitosan, the B-doping capability of boric acid, and the spatial confinement effect of Co salts, this approach achieves tailored B–C/N–C bonding configurations and precise sp²/sp³ phase modulation. It also stabilizes 15–20 nm Co nanoparticles that exhibit strong electronic coupling to the B/N-doped carbon. These effects are evidenced by DFT calculations, which reveal a 0.41 eV upshift in the Co d-band center and enhanced interfacial charge redistribution. The resulting Co/BNC catalyst demonstrates exceptional nitrate-to-ammonia conversion with 65–98% NH₃ selectivity and 462–4039 μg h⁻¹ cm⁻² rate at −0.6 to −0.1 V vs. RHE, alongside negligible activity decay surpassing noble metal benchmarks. This work establishes a scalable paradigm for multifunctional carbon electrocatalysts bridging activity, durability, and industrial viability for sustainable N remediation.