International Journal of Physics | Vol. 11, No. 2, February 2020 | pp. 9–16
DOI: 10.46882/2020/IJP/000118
Research Article
Title: Density Functional Theory Analysis of Catalytic Nitrogen Reduction on Metal-Free Nitrogen-Doped Graphene Inclusions
Names of Authors: A. L. Silva¹, Y. W. Zhang²
Authors’ Affiliations:
¹ Institute of Physics, Federal University of Rio Grande do Sul, Porto Alegre, Brazil
² Department of Physics, Tsinghua University, Beijing, China
Abstract: Electrochemical reduction of nitrogen (N²) into ammonia under ambient conditions offers a green alternative to the energy-intensive industrial Haber-Bosch process. This investigation uses density functional theory calculations to analyze the catalytic performance and reaction mechanisms of nitrogen reduction on metal-free nitrogen-doped graphene inclusions. We modeled three distinct configurations: single nitrogen substitution, double nitrogen substitution, and nitrogen-doped vacancy sites. Free energy profiles for intermediate steps leading to ammonia (NH3) were computed using the computational hydrogen electrode model across both enzymatic and consecutive pathways. The calculations demonstrate that nitrogen-doped vacancy sites lower the activation barrier for the rate-limiting nitrogenation step (*N² + H⁺ + e⁻ -> *NNH) to 0.52 eV. This value is significantly lower than the 1.45 eV barrier calculated for pristine graphene sheets. The overpotential required to trigger selective ammonia production on nitrogen vacancy sites was estimated at -0.42 V versus the standard hydrogen electrode. Charge density difference mappings show that nitrogen doping induces localized electron deficiency on adjacent carbon atoms. This electronic reconfiguration stabilizes the adsorbed intermediates. These quantum mechanical insights provide theoretical guidelines for developing metal-free, carbon-based catalysts for efficient ambient ammonia synthesis.
Keywords: Nitrogen reduction; density functional theory; nitrogen-doped graphene; electrocatalysis; reaction mechanism; overpotential
Manuscript Timeline: Received: November 02, 2019; Revised: December 18, 2019; Accepted: January 11, 2020; Published: February 14, 2020
Citation: Silva, A. L., & Zhang, Y. W. (2020). Density Functional Theory Analysis of Catalytic Nitrogen Reduction on Metal-Free Nitrogen-Doped Graphene Inclusions. International Journal of Physics, 11(2), 9–16.
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