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The creation of ordered collective vacancies in experiment proves challenging within a two-dimensional lattice, resulting in a limited understanding of their impact on catalyst performance. Motivated by the successful experimental synthesis of monolayer molybdenum borides with precisely ordered metal vacancies [Zhou et al. Science2021, 373, 801–805] through dealloying, the nitrogen reduction reaction (NRR) in monolayer borides was systematically investigated to elucidate the influence of such ordered metal vacancies on catalytic reactions and the underlying mechanisms. The results reveal that the N-containing intermediates tend to dissociate, facilitating the NRR process with reduced UL. The emergence of ordered metal vacancies modulates the electronic properties of the catalyst and partially facilitates the decomposition of N-containing intermediates. However, the ULfor NRR in Mo4/3B2and W4/3B2exhibits a significant increase. The compromised electrochemical performance is explained through the development of a simple electronic descriptor of the d–p band center (ΔdM–pB). Among these materials, Mo4/3Sc2/3B2exhibits the most superior catalytic activity with a ULof −0.5 V and favorable NRR selectivity over the HER. Our results provide mechanistic insights into the role of ordered metal vacancies in transition-metal boride for the NRR and highlight a novel avenue toward the rational design of superior NRR catalysts.

Abstract: In this work, we fabricated NiFe2O4/C composite with a coral-like structure through co-precipitation approach followed by thermal decomposition. The composite with a large surface area of 162.1 m2g−1and an average pore size of 11.8 nm was obtained. The porous structure in the composite derived from oxalate can effectively accommodate the volume changes of NiFe2O4during the cycling processes. When used as anode materials, the initial charge and discharge capacities of the composite were 926.7 and 1277.7 mAh g−1at 100 mA g−1. After 50 cycles, the reversible capacity of NiFe2O4/C could still remain at 892.4 mAh g−1. Even at a current density of 2000 mA g−1, the reversible capacity still reached 523.3 mAh g−1. The results showed that the synergy between NiFe2O4and carbon improved the electrochemical performance, and the porous composite could stabilize the structure of the electrode. Graphic Abstract:

Short extraction of metallic titanium by the electrochemical reduction process in molten salt has attracted increasing interest due to its many advantages. The electrolysis of high-purity titanium to produce lower valence titanium chlorides has so far been industrialized as balancing agents but large-scale production is still challenging due to the high cost of raw materials and easy deterioration. Herein, metallic titanium was extracted from lower valence titanium chlorides (LTCs) slurries by electrochemical reduction in molten salts. The results of LTC slurries at 260 ºC for 48 h revealed the formation of red-violet α- and γ- TiCl3with an Al content below 0.09 wt%, which gradually reduced to form metallic titanium in molten salt electrolytes. Porous metallic Ti powders were obtained from TiCl3by electrochemical reduction in KCl-LiCl-MgCl2molten salt at 400 °C. The reaction at the anode area was accompanied by TiCl4gas overflow, and continuous electrolysis of metallic titanium was achieved by supplementing the consumed TiCl3. Overall, the proposed electrolysis process looks promising for large-scale applications due to its simple electrolysis equipment, relatively stable electrolyte components, and good product quality, thereby worth further future investigation.

In this study, a novel porous 3D composite scaffold based on the biodegradable Poly(ε-caprolactone) (PCL), Polylactide Acid (PLA) and Calcium Citrate (CC) was developed via polymer blends and thermal-induced phase separation. The chemical structure, crystalline structure and micromorphology as well as mechanical strength of the scaffolds were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and tensile tests. The results show that the obtained composite scaffold present a suitable bone-like porous structure and sufficient mechanical strength. Furthermore, the release of calcium ions in Simulated Body Fluid (SBF) indicates that the composite material can provide a stable calcium-ion environment and maintain a constant pH value during the soaking process. The cell proliferation results from CCK-8 and light microscopy show that MG63 cells exhibit excellent adhesion and proliferation on the stent. At the same time, animal implantation histology confirms that the composite scaffolds have good biocompatibility in vivo. The scaffold material has greatly potential application value in the field of bone tissue engineering.

Borophane, a derivate of borophene, has been shown to eliminate the phonon imaginary frequency of borophene entirely with enhanced structural stability and be a 2D Dirac material with many appealing properties similar to its counterpart graphene. However, the mechanisms involved in borophene hydrogenation are still unclear, which are essential to borophane fabrication in experimental studies and which benefit our understanding of borophene functionalization. In this work, we investigate H2adsorption and dissociation with (without) an external field and the subsequent spillover of H atoms on borophene based on density functional theory (DFT) to shed light on the procedure of borophene hydrogenation. We find that the incorporation of positive electric fields could facilitate the borophane formation with shallower energy barriers for H2decomposition and H atoms present ultrahigh mobility on borophene under positive field. The origin of the field modulated energy barriers has been discussed. Our work provides an alternative method to hydrogenate borophene, which contributes to the application of borophane in ultrahigh speed electronic devices.

3D porous scaffold could provide suitable bone-like structure for cell adhesion and proliferation; however, surgical suffering from large volume implantation is a great challenge for patients. In this study, a shape programmable porous poly(ε-caprolactone) (PCL)-based polyurethane scaffold with memory effect was synthesized via gas foaming method, using Citrate modified Amorphous calcium Phosphate (CAP) as bioactive factor. The bending experiments indicated that the scaffolds achieved excellent shape-memory effect, which could be influenced by particle weight content. In vitro mineralization results suggested that the deposition of hydroxyapatite was promoted by scaffolds. Additionally, cell assay showed that composite scaffolds presented good cell toxicity and osteogenicity by the differentiation of rat Mesenchymal Stem Cells (rMSCs) into the osteogenic lineage. In the model of rat cranial implantation, the reparative tissue covered the defect site and bone-like structure deposited on the scaffold due to the formation of new bones. In summary, the porous smart shape-memory composite scaffolds could be a potential candidate in future distinctive bone repair applications.

In order to explore novel vanadium-based amorphous materials, a series of Li2O–V2O5–Fe2O3amorphous materials were prepared with the low-cost melting-quenching method in this report. As the main framework of amorphous materials, VO4is connected with FeO4and FeO6to form a disordered network structure. 20Li2O–60V2O5–20Fe2O3amorphous material had a stable structure and Li-ion migration channel. In the electrochemical performance test, the second cycle discharge capacity was 150.7 mAh/g at a current density of 100 mA/g and the capacity retention rate was still 80% after 100 cycles because the redox reaction between vanadium and iron ions promoted the electrochemical performance. Li2O–V2O5–Fe2O3amorphous materials are promising lithium-ion battery cathode materials.

Two-dimensional (2D) materials have been widely investigated as potential electrode materials for Na and K ion batteries because of their high specific surface area, favorable metallic conductivity, and desirable space to accommodate large metal ions. However, most of the 2D materials show limited affinity and low open-circuit voltage (OCV) toward Na and K ions, which could only be used as anodes. Development of appropriate technology to tune the OCVs of 2D materials and make them suitable for cathode application remains a great challenge. Herein, motivated by the substantial advance in experiment to control the surface atoms of 2D materials (Kamysbayev et al. Science2020, 369(6506), 979−983), we investigated the possibility of using oxygen group atoms (X = O, S, Se, and Te) to modulate the OCV and electrochemical performance of an experimentally available 2D MoB electrode. A strong combination between X atoms and MoB was identified in the resulting MoBX, retaining favorable metallic conductivity and excellent mechanical performance. The OCVs of MoBX compounds exhibit obvious surface-atom-type dependency, where Na0.5MoBO and K0.5MoBO showed average OCVs of 2.7 and 2.7 V, respectively, suitable for cathode application. In contrast, the OCVs of MoBS, MoBSe, and MoBTe are significantly smaller (0.08–0.38 V) and are only favorable for anode material application. The capacities of Na0.5MoBO and K0.5MoBO cathodes are 110 and 110 mAh/g, respectively, and the theoretical specific capacities of Na2MoBS, Na2MoBSe, and Na2MoBTe anodes are 386, 289, and 229 mAh/g, respectively. Moreover, shallow and steady intercalation/deintercalation resistance of the Na and K ions in MoBX at the dilute limit indicates excellent rate performance and high cyclic stability. These results open a new avenue and broaden the fields of endeavor to ameliorate the performance of 2D materials for cathode application.