Mo2C, the newly synthesized MXene with a large lateral size and superconductivity property, has attracted increasing interest in material science. Employing first-principles density functional calculations, its intrinsic structural, electrical, thermal, and mechanical properties are investigated in this work. It is found that this MXene is nonmagnetic with a small molar volume. The electrical conductivity is predicted in the order of 106 Ω–1m–1, and its value is significantly influenced by doping. For thermal conductivity, both of the electron and phonon contributions are studied. At room temperature, the Mo2C’s thermal conductivity is determined to be 48.4 Wm–1 K–1, which can be further enhanced by increasing temperature and introducing n-type dopants. The specific heat and thermal expansion coefficient are also assessed, and their values at room temperature are calculated as 290 Jkg–1 K–1 and 2.26 × 10–6 K–1, respectively. Moreover, the thermal contraction of the MXene is found at low temperatures. Under biaxial strains, the elastic modulus is predicted as 312 ± 10 GPa, and the ideal strength is determined to be 20.8 GPa at a critical strain of 0.086. In view of the small molar volume, superhigh electrical conductivity, favorable thermal conductivity, low thermal expansion coefficient, and high mechanical strength, the Mo2C MXene generally merits more widespread applications besides superconductors, such as applying to substrates for other layer materials, and candidate materials for batteries and supercapacitors.

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Understanding the O2 adsorption and oxidative activity on gold-based catalysts is of great significance for gold catalysis. According to the adsorption behaviors of O2 on Au(111)+, 3Au/Au(111)+, Au19 +, and Au9/CeO2(111), the electronic nature of why O2 weakly interacts with free positively charged Au substrate while it strongly interacts with Au cluster supported on ceria is well-explained herein. The ceria support serves as an electronic repository, where it gains and stores electrons from the supported metal cluster and releases them when the metal cluster interacts with molecular O2. The possible oxygen species on gold-based catalysts have been systematically confirmed for the first time. On the Au9/CeO2 modeling catalyst, a peroxide species forms when O2 locates at the hollow site of Au9, while a superoxide forms for O2 at the top site of a Ce atom. It is very interesting to find that Ce3+ ion distributions in Au n /CeO2 catalysts have diverse possibilities. The superoxide close to Au9 has the highest oxidative activity. The interface between the Au cluster and ceria surface is the active site for Au n /CeO2 catalysts. The present work sheds light on understanding the oxidative mechanism of metal/support catalysts, as well as the development of new catalysts with high performance at relatively low temperature.