Searching for suitable anodes with good performance is a key challenge for rechargeable Na-ion batteries (NIBs). Using the first-principles method, we predict that 2D nitrogen electride materials can be served as anode materials for NIBs. Particularly, we show that Ca2N meets almost all the requirements of a good NIB anode. Each formula unit of a monolayer Ca2N sheet can absorb up to four Na atoms, corresponding to a theoretical specific capacity of 1138 mAh·g(-1). The metallic character for both pristine Ca2N and its Na intercalated state NaxCa2N ensures good electronic conduction. Na diffusion along the 2D monolayer plane can be very fast even at room temperature, with a Na migration energy barrier as small as 0.084 eV. These properties are key to the excellent rate performance of an anode material. The average open-circuit voltage is calculated to be 0.18 V vs Na/Na(+) for the chemical stoichiometry of Na2Ca2N and 0.09 V for Na4Ca2N. The relatively low average open-circuit voltage is beneficial to the overall voltage of the cell. In addition, the 2D monolayers have very small lattice change upon Na intercalation, which ensures a good cycling stability. All these results demonstrate that the Ca2N monolayer could be an excellent anode material for NIBs.

ABSTRACT:Benefited from the advantages on environmental benign, easy purification, and high thermal stability, the recently synthesized two-dimensional (2D) material MoN 2 shows great potential for clean and renewable energy applications. Here, through first-principles calculations, we show that the monolayered MoN 2 is promising to be a high capacity electrode material for metal ion batteries. Firstly, identified by phonon dispersion and exfoliation energy calculations, MoN 2 monolayer is proved to be structurally stable and could be exfoliated from its bulk counterpart in experiments.Secondly, all the studied metal atoms (Li, Na and K) can be adsorbed on MoN 2 monolayer, with both pristine and doped MoN 2 being metallic. Thirdly, the metal atoms possess moderate/low migration barriers on MoN 2 , which ensures excellent cycling performance as a battery electrode. In addition, the calculated average voltages suggest that MoN 2 monolayer is suitable to be a cathode for Li-ion battery and anodes for Na-ion and K-ion batteries. Most importantly, as a cathode for Li-ion battery, MoN 2 possesses a comparable average voltage but a 1-2 times larger capacity (432 mA h g -1 ) than usual commercial cathode materials; as an anode for Na-ion battery, the theoretical capacity (864 mA h g -1 ) of MoN 2 is 2-5 times larger than typical 2D anode materials such as MoS 2 and most MXenes. Finally we also provide an estimation of capacities for other transition-metal dinitrides materials. Our work suggests that the transition-metal dinitrides MoN 2 is an appealing 2D electrode materials with high storage capacities.

Members of the ERF transcription factor family play important roles in regulating gene expression in response to biotic and abiotic stresses. In soybean (Glycine max L.), however, only a few ERF genes have been studied so far. In this study, 98 unigenes that contained a complete AP2/ERF domain were identified from 63 676 unique sequences in the DFCI Soybean Gene Index database. The phylogeny, gene structures, and putative conserved motifs in soybean ERF proteins were analysed, and compared with those of Arabidopsis and rice. The members of the soybean ERF family were divided into 12 subgroups, similar to the case for Arabidopsis. AP2/ERF domains were conserved among soybean, Arabidopsis, and rice. Outside the AP2/ERF domain, many soybean-specific conserved motifs were detected. Expression analysis showed that nine unigenes belonging to six ERF family subgroups were induced by both biotic/abiotic stresses and hormone treatment, suggesting that they were involved in cross-talk between biotic and abiotic stress-responsive signalling pathways. Overexpression of two full-length genes from two different subgroups enhanced the tolerances to drought, salt stresses, and/or pathogen infection of the tobacco plants. These results will be useful for elucidating ERF gene-associated stress response signalling pathways in soybean.