Abstract
Nitrogen-doped graphene (NG) has attracted increasing attention because its properties are significantly different to pristine graphene, making it useful for various applications in physics, chemistry, biology, and materials science. However, the NGs that can currently be fabricated using most experimental methods always have low N concentrations and a mixture of N dopants, which limits the desirable physical and chemical properties. In this work, first principles calculations combined with the local particle-swarm optimization algorithm method were applied to explore possible stable structures of 2D carbon nitrides (C1−xNx) with various C/N ratios. It is predicted that C1−xNx structures with low N-doping concentration contain both graphitic and pyridinic N based on their calculated formation energies, which explains the experimentally observed coexistence of graphitic and pyridinic N in NG. However, pyridinic N is predominant in C1−xNx when the N concentration is above 0.25. In addition, C1−xNx structures with low N-doping concentration were found to have considerably lower formation energies than those with a high N concentration, which means synthesized NGs with low N-doping concentration are favorable. Moreover, we found the restrictions of mixed doping and low N concentration can be circumvented by using different C and N feedstocks, and by growing NG at lower temperatures.
Highlights
Due to its high carrier mobility of more than 1.5 × 104 cm[2] V−1 s−1 at room temperature, graphene is a promising material for future high-speed transistors[1]
We systematically studied the stable structures of carbon nitride with different C/N ratios (C1−xNx, 0 < x < 1), based on the particle-swarm optimization (PSO) algorithm[16] and density functional theory (DFT) calculations
Effect of N type and concentration on C1−xNx stability Generally, there are three bonding configurations that appear in the Nitrogen-doped graphene (NG) lattice
Summary
Due to its high carrier mobility of more than 1.5 × 104 cm[2] V−1 s−1 at room temperature, graphene is a promising material for future high-speed transistors[1]. We found that graphitic N and pyridinic N in 2D C1−xNx structures have comparable formation energies at low N-doping concentrations.
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