The metal atomic substitution induced half-metallic properties, metallic properties and semiconducting properties in X-N4 nanoribbons.

Armchair X-N4 nanoribbons (X-AN4NRs) and zigzag X-N4 nanoribbons (X-ZN4NRs) were calculated using first-principles calculations. Ferromagnets (FM) were found to be the most stable among the initial magnetic structures. Furthermore, nanoribbons were found to be thermodynamically stable through molecular dynamics simulations. It can be found that when the temperature and total energy of X-AN4NRs and X-ZN4NRs change with time, they have a small oscillation range, which confirms the dynamic stability of X-AN4NRs and X-ZN4NRs under realistic experimental conditions. Subsequently, the magnetic moment analysis of the X-AN4NRs and X-ZN4NRs revealed that the magnetic moment of the X-AN4NRs is significantly smaller than that of X-ZN4NRs. The band structure and density of states (DOS) of the X-AN4NRs and X-ZN4NRs were also computed, which indicate different properties for different transition metal nanoribbons. The results suggest that different edge structures and transition metals can influence the electronic structure of the nanoribbons. Moreover, based on the band structure and DOS, it was found that Mn-AN4NRs and Fe-ZN4NRs exhibit half-metallic properties. They can generate 100% polarized currents at the Fermi level, providing valuable information for developing spintronic devices. Our study has a positive value for regulating the properties of the nanoribbons by metal atom substitution.

Tailored modifications of the electronic properties of g-C3N4/C2N-h2D nanoribbons by first-principles calculations.

The electronic structure of g-C3N4/C2N-h2D nanoribbons was investigated by first-principles calculations. As a splice structure, we first computed the three magnetic coupled states of g-C3N4/C2N-h2D nanoribbons. After self-consistent calculations, both the antiferromagnetic and paramagnetic coupling states become ferromagnetic coupling states. It was proved that the ferromagnetic coupling state is the most stable state. Thermodynamic stability was subsequently verified based on the ferromagnetic coupling state. It had a steady electron spin polarization, with a magnetic moment of 1 µB for each primitive cell. It changed from a direct band-gap semiconductor to an indirect band-gap semiconductor and exhibited the properties of a narrow band gap semiconductor through the analysis of the energy band and charge density. To transform the electronic structure, we adsorbed different transition metals in g-C3N4/C2N-h2D nanoribbons. We investigated the electronic structure of g-C3N4/C2N-h2D nanoribbons adsorbed by different transition metals. It was shown that the electronic structure of g-C3N4/C2N-h2D nanoribbons could be regulated by the adsorption of different transition metal atoms. Moreover, the adsorption of Fe and Ni can generate a 100% polarized current in the Fermi surface, which will provide more application potential for spintronics devices.

Doping atom improves photocatalytic performance in a new metal-free organic photocatalyst for water splitting.

Photocatalytic water splitting, using solar energy to obtain hydrogen, is an ideal technology for producing new energy. In the process of photocatalysis, the improvement of the catalytic performance of the catalysts used is a matter of great concern to scientists. So far, there are many problems preventing improvements in photocatalytic performance. In this paper, we propose an atom-doping method, which is an effective method to improve the catalytic performance. We present a type of graphene-like carbon nitride material, whose primitive cell is composed of 12 carbon atoms and 14 nitrogen atoms, so it is denoted as g-C12N14. The energy band, density of states, and optical absorption spectrum of g-C12N14 have been studied using first-principles calculations. From the characteristics of these properties, it is concluded that g-C12N14 can be used as a photocatalyst, but its catalytic performance is low. To improve the catalytic performance, atom doping has been used, which can change the electronic state of the surface to enhance the activity of the photocatalyst. It was calculated that the doped phosphorus and boron system improved the optical absorption range, thus improving the photocatalytic efficiency. To make the results more accurate, all the calculations used the computationally-large HSE06 hybrid functional method.