Based on the ReaxFF reactive potential, the interaction of O2 molecules with three types of surfaces (100, 110, 111) of ferritic Fe–Cr alloy has been studied by classical molecular dynamics at constant O2 concentrations and temperatures.

Controlling oxygen deficiencies is essential for the development of novel chemical and physical properties such as high-T c superconductivity and low-dimensional magnetic phenomena. Among reduction methods, topochemical reactions using metal hydrides (e.g., CaH2) are known as the most powerful method to obtain highly reduced oxides including Nd0.8Sr0.2NiO2 superconductor, though there are some limitations such as competition with oxyhydrides. Here we demonstrate that electrochemical protonation combined with thermal dehydration can yield highly reduced oxides: SrCoO2.5 thin films are converted to SrCoO2 by dehydration of HSrCoO2.5 at 350 °C. SrCoO2 forms square (or four-legged) spin tubes composed of tetrahedra, in contrast to the conventional infinite-layer structure. Detailed analyses suggest the importance of the destabilization of the SrCoO2.5 precursor by electrochemical protonation that can greatly alter reaction energy landscape and its gradual dehydration (H1–x SrCoO2.5–x/2) for the SrCoO2 formation. Given the applicability of electrochemical protonation to a variety of transition metal oxides, this simple process widens possibilities to explore novel functional oxides.

Exploiting two-dimensional (2D) metallic electrodes with high energy density and fast rate performance is crucial in rechargeable ion batteries. Herein, the electronic properties of 2D monolayer Ta 2 CS 2 and its potential performance as 2D electrode candidate in Li + , Na + , K + , and Ca 2+ ion batteries have been examined by utilizing first-principles calculations. The exfoliation of metallic monolayer Ta 2 CS 2 is feasible owing to small cleavage energy of 0.64 J/m 2 and thermodynamical stability. The Ta 2 CS 2 −metal atom complexes are energetically favorable through examining adsorption energies. Furthermore, the low diffusion barriers of 0.21 eV for Li and 0.09 eV for Na and the high specific capacity of 367.23 mA h/g could be achieved. In particular, the low average opencircuit voltage of 0.45 V for Na implies 2D Ta 2 CS 2 to be a suitable anode candidate in Naion batteries. These results provide fundamental insights for 2D Ta 2 CS 2 in the field of energy conversion and storage. KEYWORDS: two-dimensional Ta 2 CS 2 , anode material, diffusion barrier, rechargeable ion batteries, first principles calculations

A molecularly thin electrolyte is developed to demonstrate a nonvolatile, solid-state, one-transistor (1T) memory based on an electric-double-layer (EDL) gated WSe2 field-effect transistor (FET). The custom-designed monolayer electrolyte consists of cobalt crown ether phthalocyanine and lithium ions, which are positioned by field-effect at either the surface of the WSe2 channel or an h-BN capping layer to achieve “1” or “0”, respectively. Bistability in the monolayer electrolyte memory is significantly improved by the h-BN cap with density functional theory (DFT) calculations showing enhanced trapping of Li+ near h-BN due to a ∼1.34 eV increase in the absolute value of the adsorption energy compared to vacuum. The threshold voltage shift between the two states corresponds to a change in charge density of ∼2.5 × 1012 cm–2, and an On/Off ratio exceeding 104 at a back gate voltage of 0 V. The On/Off ratio remains stable after 1000 cycles and the retention time for each state exceeds 6 h (max measured). When the write time approaches 1 ms, the On/Off ratio remains >102, showing that the monolayer electrolyte-gated FET can respond on time scales similar to existing flash memory. The data suggest that faster switching times and lower switching voltages could be feasible by top gating.

A phonon is the medium a bulk material used to exchange energy with the environment and is thus crucial for heterogeneous catalysis. However, a physical correlation between phonons and catalytic processes has not been established yet. Herein, by combining various in situ characterization techniques, we discovered the intrinsic correlations between phonon modes and the vibrations of reactant intermediates during NO oxidation on the mullite catalyst YMn2O5. It was found that the active phonon modes (350 (Ag(5)) and 670 cm–1 (B1g(12))) are strongly correlated with the vibrational frequencies of the adsorbed −O2 and −O–NO2 intermediates. The resulting resonance will transfer the superposed energy (nℏω) of the high-energy phonons to reactants one by one via the unit energy (ℏω) and then increase the vibrational amplitude along the reaction direction, contributing to the increase in the entropy of the surface reactants and thus the reduction of the Gibbs energy of activation. Phonon resonance catalysis (PRCAT) was thus proposed based on this discovery. This work provides insights into the bidirectional selection of catalysts and precise chemical reactions by matching catalyst phonons with reactant vibrational frequencies.