The interaction of two-dimensional α- and β-phosphorus carbide with environmental molecules: a DFT study

Atomic insights into the interaction of N2, CO2, NH3, NO, and NO2 gas molecules with Zn2(V, Nb, Ta)N3 ternary nitride monolayers

The search for promising carrier blocking layer materials with high stability, including resistance to surface inhibition by environmental molecules that cause a drop in carrier mobility, is critical for the production of tandem solar cells. Based on density functional theory calculations, the reaction of atmospheric gases, including N2, CO2, NH3, NO, and NO2, with three promising Zn2(V, Nb, Ta)N3 monolayers is discovered. The results suggest the chemical adsorption of NH3 and physical adsorption of NO and NO2. In addition, the Zn2(V, Nb, Ta)N3 monolayers are characterized by a weak bonding with N2 and CO2. Charge redistribution is found at the interface between the monolayers and NH3, NO and NO2 molecules, leading to the formation of a local surface dipole that affects the functionality of the Zn2(V, Nb, Ta)N3 monolayers. The Zn2VN3 monolayer is less reactive with atmospheric gases and thus is the most promising for application in tandem solar cells. Notably, the revealed nontrivial behavior of the Zn2(V, Nb, Ta)N3 monolayers towards N-containing gases makes them promising for application in gas sensing. Specifically, the Zn2TaN3 monolayer is the most promising for application in molecular sensing due to its high reversibility and distinguished interaction with NH3, NO, and NO2 gases.

Role of transition metal d-orbitals in single-atom catalysts for nitric oxide electroreduction to ammonia

Recently, surging interests exist in direct electrochemical ammonia (NH₃) synthesis from nitric oxide (NO) due to the dual benefit of NH₃ synthesis and NO removal. However, designing highly efficient catalysts is still challenging. Based on density functional theory, the best ten candidates of transition-metal atoms (TMs) embedded in phosphorus carbide (PC) monolayer is screened out as highly active catalysts for direct NO-to-NH₃ electroreduction. The employment of machine learning-aided theoretical calculations helps to identify the critical role of TM-d orbitals in regulating NO activation. A V-shape tuning rule of TM-d orbitals for the Gibbs free energy change of NO or limiting potentials is further revealed as the design principle of TM embedded PC (TM-PC) for NO-to-NH₃ electroreduction. Moreover, after employing effective screening strategies including surface stability, selectivity, the kinetic barrier of potential-determining step, and thermal stability comprehensively studied for the ten TM-PC candidates, only Pt embedded PC monolayer has been identified as the most promising direct NO-to-NH₃ electroreduction with high feasibility and catalytic performance. This work not only offers a promising catalyst but also sheds light on the active origin and design principle of PC-based single-atom catalysts for NO-to-NH₃ conversion.

Anisotropic Carrier Mobility and Spectral Fingerprints of Two-Dimensional γ-Phosphorus Carbide with Antisite Defects

We apply density functional theory to study carrier mobility in a γ-phosphorus carbide monolayer. Although previous calculations predicted high and anisotropic mobility in this material, we show that the mobility can be significantly influenced by common antisite defects. We demonstrate that at equilibrium concentrations defects do not inhibit carrier mobility up to temperatures of 1000 K. However, defects can change the mobility at high nonequilibrium concentrations of about 10^-4 to 10^-2 defects per atom. At the low end of this concentration range, defects act as traps for charge carriers and inhibit their mobility. At the high end of this range, defects change the effective carrier masses and deformation potentials, and they can lead to both an increase and a decrease in mobility. We also report the Raman and IR spectra associated with antisite defects. We predict new vibrational modes and shifts of the existing modes due to the defects.

Family of Two-Dimensional Transition Metal Dichlorides: Fundamental Properties, Structural Defects, and Environmental Stability

A large number of novel two-dimensional (2D) materials are constantly being discovered and deposited in databases. Consolidated implementation of machine learning algorithms and density functional theory (DFT)-based predictions have allowed the creation of several databases containing an unimaginable number of 2D samples. As the next step in this chain, the investigation leads to a comprehensive study of the functionality of the invented materials. In this work, a family of transition metal dichlorides have been screened out for systematic investigation of their structural stability, fundamental properties, structural defects, and environmental stability via DFT-based calculations. The work highlights the importance of using the potential of the invented materials and proposes a comprehensive characterization of a new family of 2D materials.

First-Principles Prediction of Two-Dimensional B3C2P3 and B2C4P2: Structural Stability, Fundamental Properties, and Renewable Energy Applications

The existence of two novel hybrid two-dimensional (2D) monolayers, 2D B₃C₂P₃ and 2D B₂C₄P₂, has been predicted based on the density functional theory calculations. It has been shown that these materials possess structural and thermodynamic stability. 2D B₃C₂P₃ is a moderate band gap semiconductor, while 2D B₂C₄P₂ is a zero band gap semiconductor. It has also been shown that 2D B₃C₂P₃ has a highly tunable band gap under the effect of strain and substrate engineering. Moreover, 2D B₃C₂P₃ produces low barriers for dissociation of water and hydrogen molecules on its surface, and shows fast recovery after desorption of the molecules. The novel materials can be fabricated by carbon doping of boron phosphide and directly by arc discharge and laser ablation and vaporization. Applications of 2D B₃C₂P₃ in renewable energy and straintronic nanodevices have been proposed.