Ultrathin Bismuth Nanosheets for Stable Na-Ion Batteries: Clarification of Structure and Phase Transition by in Situ Observation

Advances of 2D bismuth in energy sciences

Since graphene has been successfully exfoliated, two-dimensional (2D) materials constitute a vibrant research field and open vast perspectives in high-performance applications. Among them, bismuthene and 2D bismuth (Bi) are unique with superior properties to fabricate state-of-the-art energy saving, storage and conversion devices. The largest experimentally determined bulk gap, even larger than those of stanene and antimonene, allows 2D Bi to be the most promising candidate to construct room-temperature topological insulators. Moreover, 2D Bi exhibits cyclability for high-performance sodium-ion batteries, and the enlarged surface together with the good electrochemical activity renders it an efficient electrocatalyst for energy conversion. Also, the air-stability of 2D Bi is better than that of silicene, germanene, phosphorene and arsenene, which could enable more practical applications. This review aims to thoroughly explore the fundamentals of 2D Bi and its improved fabrication methods, in order to further bridge gaps between theoretical predictions and experimental achievements in its energy-related applications. We begin with an introduction of the status of 2D Bi in the 2D-material family, which is followed by descriptions of its intrinsic properties along with various fabrication methods. The vast implications of 2D Bi for high-performance devices can be envisioned to add a new pillar in energy sciences. In addition, in the context of recent pioneering studies on moiré superlattices of other 2D materials, we hope that the improved manipulation techniques of bismuthene, along with its unique properties, might even enable 2D Bi to play an important role in future energy-related twistronics.

Electrochemical exfoliation from an industrial ingot: ultrathin metallic bismuth nanosheets for excellent CO2 capture and electrocatalytic conversion

Formic acid (or formate) is a liquid fuel and chemical feedstock, and it is considered as one of the most useful value-added reductive products from electrochemical CO2 conversion. Green metallic Bi nanosheets are believed be a promising candidate for formic acid production in CO2 electroreduction. However, the complexity of their preparation with a low yield hinders their practical application on a large scale. Herein, we report that by using a cheap and commonly used industrial ingot, phase-pure two-dimensional bismuth nanosheets are fabricated on a large scale by a rapid electrochemical cathodic exfoliation method. In addition to featuring abundant active sites, the obtained Bi nanosheets possess exceptionally high adsorption capacity to CO2 compared to its bulk counterpart, resulting in remarkable enhancement in CO2 electroreduction with high selectivity toward formic acid over a wide range of negative potentials, high current density and satisfactory durability. This facile strategy opens a promising avenue for massive fabrication of metallic Bi nanosheets with excellent electrocatalytic performance for large-scale commercial utilization of CO2.

Density functional study of Li/Na adsorption properties of single-layer and double-layer antimonenes

β-Antimonene, a stable two-dimensional material, has been successfully prepared recently. Experiments have demonstrated β-antimonene's excellent Li storage properties. Based on first-principles density functional theory (DFT), the adsorption properties of Li/Na atoms on single-layer antimonene (SL-Sb) and double-layer antimonene (DL-Sb) have been studied. The optimal adsorption position of Li/Na atoms on SL-Sb is the V site with an adsorption energy of 1.91/1.46 eV. With the increase of Li adsorption density, the crystal structure of the antimonene changes significantly. The optimal adsorption position of Li on DL-Sb is the V2 site in the interlayer with an adsorption energy of 2.71 eV, and that of Na is the V1 site outside the surface with an adsorption energy of 1.72 eV. With the increase of the adsorption density of Li, the antimonene presented a trend of forming an alloy. Whereas with the increase of Na adsorption density, the antimonene retains its original structure. The diffusion barrier of Li/Na atoms on the SL-Sb surface is 0.22/0.13 eV, and outside the DL-Sb surface is 0.25/0.15 eV. In short, DL-Sb can maintain a stable structure with a large Li/Na storage density; the diffusion barriers of Li/Na atoms on antimonene are relatively low, which is beneficial to the rapid insertion/extraction.

β-Antimonene, a stable two-dimensional material, has been successfully prepared recently.

2D V-V Binary Materials: Status and Challenges

2D phosphorene, arsenene, antimonene, and bismuthene, as a fast-growing family of 2D monoelemental materials, have attracted enormous interest in the scientific community owing to their intriguing structures and extraordinary electronic properties. Tuning the monoelemental crystals into bielemental ones between group-VA elements is able to preserve their advantages of unique structures, modulate their properties, and further expand their multifunctional applications. Herein, a review of the historical work is provided for both theoretical predictions and experimental advances of 2D V-V binary materials. Their various intriguing electronic properties are discussed, including band structure, carrier mobility, Rashba effect, and topological state. An emphasis is also given to their progress in fabricated approaches and potential applications. Finally, a detailed presentation on the opportunities and challenges in the future development of 2D V-V binary materials is given.