We systematically investigated the structure, electronic properties, zone-center phonon modes, and structure instability of four cubic perovskite BiMO 3 compounds, with three of the M ions being IIIB metals ͑Al, Ga, and In͒ and one IIIA transition-metal Sc, using first-principles density-functional calculations. Optimized lattice parameters, bulk moduli, band structures, densities of states, as well as charge density distributions are calculated and compared with the available theoretical data. Our results are in good agreement with those previously reported in the literature. All the BiMO 3 oxides considered in the present work are semiconductors with an indirect band gap between the occupied O 2p and unoccupied Bi 6p states varying between 0.17 and 1.57 eV. Their electronic properties are determined mainly by Bi-O bonding, which, in turn, depends on the M -O bonding. Ferroelectric properties of these oxides come from the 6s 2 lone pair on the A-site Bi ion and is similarly affected by the M ions through their influence on the Bi-O bonding, as suggested by our calculations of density of state, Born effective charge, and soft modes. The existence of soft modes and eight ͓111͔ minima suggests that the phase transition in BiAlO 3 has a mixed displacive and order-disorder character. There is evidence that ferroelectricity is absent in BiGaO 3 . Our investigation suggests that the BiMO 3 oxides or their modified versions are promising ferroelectric, piezoelectric, multiferroic, and photocatalytic materials.

Manganese dioxide (MnO2), with naturally abundant crystal phases, is one of the most active candidates for toluene degradation. However, it remains ambiguous and controversial of the phase–activity relationship and the origin of the catalytic activity of these multiphase MnO2. In this study, six types of MnO2 with crystal phases corresponding to α‐, β‐, γ‐, ε‐, λ‐, and δ‐MnO2 are prepared, and their catalytic activity toward ozone‐assisted catalytic oxidation of toluene at room temperature are studied, which follow the order of δ‐MnO2 > α‐MnO2 > ε‐MnO2 > γ‐MnO2 > λ‐MnO2 > β‐MnO2. Further investigation of the specific oxygen species with the toluene oxidation activity indicates that high catalytic activity of MnO2 is originated from the rich oxygen vacancy and the strong mobility of oxygen species. This work illustrates the important role of crystal phase in determining the oxygen vacancies’ density and the mobility of oxygen species, thus influencing the catalytic activity of MnO2 catalysts, which sheds light on strategies of rational design and synthesis of multiphase MnO2 catalysts for volatile organic pollutants’ (VOCs) degradation.

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Highlights A novel amide-based nonflammable electrolyte is proposed. The formation mechanism and solvation chemistry are investigated by molecular dynamics simulations and density functional theory. An inorganic/organic-rich solid electrolyte interphase with an abundance of LiF, Li3N and Li–N–C is in situ formed, leading to spherical lithium deposition. The amide-based electrolyte can enable stable cycling performance at room temperature and 60 ℃. Abstract The formation of lithium dendrites and the safety hazards arising from flammable liquid electrolytes have seriously hindered the development of high-energy-density lithium metal batteries. Herein, an emerging amide-based electrolyte is proposed, containing LiTFSI and butyrolactam in different molar ratios. 1,1,2,2-Tetrafluoroethyl-2,2,3,3-tetrafluoropropylether and fluoroethylene carbonate are introduced into the amide-based electrolyte as counter solvent and additives. The well-designed amide-based electrolyte possesses nonflammability, high ionic conductivity, high thermal stability and electrochemical stability (> 4.7 V). Besides, an inorganic/organic-rich solid electrolyte interphase with an abundance of LiF, Li3N and Li–N–C is in situ formed, leading to spherical lithium deposition. The formation mechanism and solvation chemistry of amide-based electrolyte are further investigated by molecular dynamics simulations and density functional theory. When applied in Li metal batteries with LiFePO4 and LiMn2O4 cathode, the amide-based electrolyte can enable stable cycling performance at room temperature and 60 ℃. This study provides a new insight into the development of amide-based electrolytes for lithium metal batteries.