MC2 (M = Y, Zr, Nb, and Mo) monolayers containing C2 dimers: prediction of anode materials for high-performance sodium ion batteries

First-Principles Calculations of TiB4 and TiB5 as Anodes with High Capacity for Na-Ion Batteries

The electrochemical properties of TiB4 and TiB5 monolayers in Na-ion batteries (NIBs) were studied by using the first-principles calculation method based on density functional theory. The TiB4/TiB5 monolayer showed excellent Na storage capacity, capable of adsorbing two layers of Na with theoretical capacities of 1176.77 and 1052.05 mA g-1, respectively. The average operating voltages of the TiB4 and TiB5 monolayers are 0.073 and 0.042 eV, respectively, indicating that they can be used as anode materials for NIBs. More interestingly, the exposed B surface not only brings a high theoretical capacity but also provides a relatively small diffusion barrier of 0.16 (for TiB4) and 0.33 eV (for TiB5), enhancing their rate capability in NIBs.

Computational Design of a Two-Dimensional Copper Carbide Monolayer as a Highly Efficient Catalyst for Carbon Monoxide Electroreduction to Ethanol

Rationally designing stable and low-cost electrocatalysts with high efficiency is of great significance for the large-scale electrochemical reduction of carbon monoxide (eCOR) to high-value-added multicarbon products. Inspired by the tunable atomic structures, abundant active sites, and excellent properties of two-dimensional (2D) materials, in this work, we designed several novel 2D C-rich copper carbide materials as eCOR electrocatalysts by performing an extensive structural search and comprehensive first-principles computations. According to the computed phonon spectra, formation energies, and ab initio molecular dynamics simulations, we screened out two highly stable candidates, i.e., CuC₂ and CuC₅ monolayers with metallic features. Interestingly, the predicted 2D CuC₅ monolayer exhibits superior eCOR performance for C₂H₅OH synthesis with high catalytic activity (low limiting potential of -0.29 V and small activation energy for C-C coupling of 0.35 eV) and high selectivity (significant suppressing effect on the side reactions). Thus, we predicted that the CuC₅ monolayer holds great potential as an eligible electrocatalyst for CO conversion to multicarbon products, which could motivate more study to develop highly efficient electrocatalysts in similar binary noble-metal compounds.

Biphenylene monolayer: a novel nonbenzenoid carbon allotrope with potential application as an anode material for high-performance sodium-ion batteries

Allotrope metal structures composed of carbon as anode materials for metal-ion batteries are a current research hotspot. In this work, the recently synthesized graphene allotrope, two-dimensional (2D) biphenylene, consisting of tetragonal, hexagonal and octagonal carbon rings, was explored theoretically. Our first-principles calculations verified that 2D biphenylene has dynamical, mechanical and thermal stability and exhibits metallic features. Its novel structure can provide multiple adsorption sites for Na ions, a fast charge-discharge rate (low Na migration barriers of <0.2 eV) and high theoretical capacity (1075.37 mA h g^-1). These superior properties, combined with its carbon abundance and light mass, make the biphenylene monolayer a promising high-performance anode for sodium-ion batteries (SIBs).