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The doping of transition metals can effectively modulate the electronic structures and enhance the photocatalytic activity of MXenes. The electronic and photocatalytic properties, as well as the quantum capacitance of Sc2CO2-Y under biaxial strain, were studied by density functional theory. Sc2CO2-Y is a direct semiconductor and keeps its semiconductor character under strain. Sc2CO2-Y under tensile strain has higher photocatalytic activity than under compressive strain. In particular, Sc2CO2-Y at 2% strain has the slowest recombination rate of electrons and holes because of the largest. Sc2CO2-Y under strain is a potential cathode material. Its large potential keeps the character of cathode materials for Sc2CO2-Y under strain. Sc2CO2-Y under tensile strain has better conductivity, especially under 5% strain, due to having the largest Re (ε0). Sc2CO2-Y under strain can perform the HER, but fails to perform the OER at pH = 0, and tensile strain increases the reduction capacity of Sc2CO2-Y. Under strains from −2% to 2%, Sc2CO2-Y can perform the OER in an alkaline environment. Sc2CO2-Y is a good CO2 photocatalyst in acidic environments; the increase of pH value weakens the N2 reducing capacity of Sc2CO2-Y under strain. Its work function, charge transfer and optical properties are also explored. [ABSTRACT FROM AUTHOR]

Bulk phosphorus oxynitride (PON), isoelectronic with SiO2, is confirmed to have many polymorphs as the latter. However, its 2D counterparts have not been studied. In this work, crystal structure exploration and property study are performed on 2D PON with the help of first‐principle calculation. Three 2D PON sheets are found with thermal, dynamical, and mechanical stability and all of them can be viewed as oxygen‐doped known 2D γ phosphorus nitride (γ‐PN). In the studies, it is indicated that they are indirect bandgap materials with gap values larger than 3 eV. The situations of orbital hybridization are discussed and their bonding properties are analyzed. Infrared vibrational spectra of these 2D materials are simulated and the vibrational modes at the Brillouin center are assigned by the factor group analysis. The reasons for the disappearance of some infrared peaks in the simulated spectra are revealed based on the calculated Born effective charges and vibrational eigenvectors. Their piezoelectric stress tensors are computed via density‐functional perturbation method and the piezoelectric strain tensors are also deduced via the calculated elastic constants. In the results, it is uncovered that these 2D PON sheets have considerably greater piezoelectric coefficients than the primitive 2D γ‐PN, which make them promising for nanopiezoelectric use. [ABSTRACT FROM AUTHOR]

MXenes have superior catalytic activities, because of their excellent electronic properties. In this work, the electronic properties, quantum capacitance, and photocatalytic activity of Pt-doped Zr2CO2 (Pt-VO-Zr2CO2) nanosheets under biaxial strain are investigated by first-principles calculations. Pt-VO-Zr2CO2 are all indirect semiconductors under compressive strain and are direct semiconductors under tensile strain except at 10%. The red shift of Zr-d and O-p orbitals in conduction bands results in the decrease of band gaps under compressive strain. Pt-VO-Zr2CO2 under strain except at −8% are cathode materials in an aqueous system, especially for Pt-VO-Zr2CO2 with +10% strain with the maximum storage charge. Pt-VO-Zr2CO2 under strain can reduce water at pH 0 and perform overall water splitting in a neutral environment. Pt-VO-Zr2CO2 nanosheets with a strain larger than +4% can reduce CO2 to all products, and tensile strain enhances CO2 photocatalysis. The N2 reduction capability of Pt-VO-Zr2CO2 reduces in a neutral environment. [ABSTRACT FROM AUTHOR]

BiOX (X = Cl, Br, I) monolayers are photocatalytic materials having many potential applications, but their basic properties are still not systematically studied. Herein, first‐principles calculations are performed to study their electronic, mechanical, and infrared properties. Band structures calculated by the Heyd–Scuseria–Ernzerhof (HSE06) functional with and without spin orbital coupling uncover that they are indirect bandgap materials. Partial densities of states of these materials are computed and compared to reveal the reason for the differences among their band structures. Studies imply that the BiO bonds are chiefly covalent while the interaction between the Bi and the X atoms is mainly ionic. Elastic constants and ideal in‐plane stresses of these materials are computed to explore their mechanical properties. Performed factor group analyses indicate that there are nine Raman‐active and six infrared‐active modes in their Brillouin zone centers. Their infrared spectra are simulated and the reason for the disappearance of some infrared peaks is given. Comparisons on the above properties are also made for these BiOX monolayers. [ABSTRACT FROM AUTHOR]