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. Science 2020, 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 Na 0.5 MoBO and K 0.5 MoBO 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 Na 0.5 MoBO and K 0.5 MoBO cathodes are 110 and 110 mAh/g, respectively, and the theoretical specific capacities of Na 2 MoBS, Na 2 MoBSe, and Na 2 MoBTe 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.

In this study, a novel polyurethane porous 3D scaffold based on polyethylene glycol (PEG) and polytetrahydrofuran glycol (PTMG) was developed by in situ polymerization and freeze drying. Aliphatic hexamethylene diisocyanate (HDI) as a nontoxic and safe agent was adopted to produce the rigid segment in polyurethane polymerization. The chemical structure, macrostructure, and morphology—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 HDI can react mildly with hydroxyl (–OH) groups of PEG and PTMG, while gas foaming action caused by the release of CO2 occurred simultaneously in the reactive process, resulting in a uniform porous structure of PU scaffold. Moreover, the scaffolds were soaked in water and freeze dried to obtain higher porosity and more interconnective microstructures. The scaffolds have a porosity of over 70% and pore size from 100 to 800 μm. The mechanical properties increased with increasing PEG content, while the hydrophilicity increased as well. After immersion in simulated body fluid (SBF), the scaffolds presented a stable surface structure. The gas foaming/freezing drying process is an excellent method to prepare skin tissue engineering scaffold from PTMG/PEG materials with high porosity and good inter connectivity.

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