Achieving 78.2 % Faraday Efficiency for Electrochemical Ammonia Production Via Covalent Modification of CNTs with B4C

carbon nanotubes (CNTs) have been demonstrated to have far-reaching applications in modifying electrodes, and electrocatalysts due to their high surface area and high mobility for charge carriers. Present study shows a catalyst constructed from covalent modification of CNTs with B₄C for electrochemical nitrogen reduction. The formation of new C−B−O covalent bonds was verified by a series of characterizations.

Abstract

Electrochemical reduction of N₂ to NH₃ provides an alternative to the Haber-Bosch process for sustainable NH₃ production driven by renewable electricity. Here, we reported carbon nanotubes (CNTs) covalently modified with boron carbide (B₄C) as a nonmetallic catalyst for efficient electrochemical nitrogen reduction reaction (NRR) under ambient conditions. The structure of the catalyst was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), elemental mapping, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The catalyst held a superior selectivity for NRR with high Faraday efficiency of 78.2 % accompanying with NH₃ yield rate of 14.0 μg mg⁻¹ _cat. h⁻¹ under the condition of 0.1 M Na₂SO₄ and −0.6 V vs. RHE. Electrochemical experiments including cyclic voltammetry, electrochemical impedance spectroscopy and Tafel polarization curves were performed to explain the best electrochemical properties of B₄C/CNTs among the samples. This work demonstrates that the strategy of covalent modification plays an important role to improve the selectivity of electrochemical NRR catalyst, thus allowing the reactions to proceed more efficiently.

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