Zhang Feng, Jia Congying, Zhang Nan, He Xuexia, Li Qi, Sun Jie, Jiang Ruibin, Lei Zhibin, Liu Zong-Huai
Key Laboratory of Applied Surface and Colloid Chemistry (Shaanxi Normal University), Ministry of Education, Xi'an, 710062, P. R. China.
Shaanxi Key Laboratory for Advanced Energy Devices, Xi'an, 710119, P. R. China.
Nanoscale. 2022 Mar 17;14(11):4195-4203. doi: 10.1039/d1nr07353b.
By using I as an oxidant and CHCN as a reaction medium, few-layer Mg-deficient borophene nanosheets (FBN) with a stoichiometric ratio of MgB are prepared by oxidizing MgB in a mixture of CHCN and HCl for 14 days under nitrogen protection and followed by ultrasonic delaminating in CHCN for 2 h. The prepared FBN possess a two-dimensional flake morphology, and they show a clear interference fringe with a -spacing of 0.251 nm corresponding to the (208) plane of rhombohedral boron. While maintaining the hexagonal boron networks of MgB, the FBN have an average thickness of about 4.14 nm (four monolayer borophene) and a lateral dimension of 500 nm, and the maximum Mg deintercalation rate can reach 78%. The acidity of the reaction system plays an important role; the HCl reaction system not only facilitates the oxidation of MgB by I, but also increases the deintercalation ratio of Mg atoms. Etching of the Mg atom layer with HCl, the negative charge decrease of the boron layer by I oxidation, and the Mg chelating effect from CHCOOH due to the hydrolysis of CHCN in an HCl environment led to a high deintercalation rate of the Mg atom. Density functional theory (DFT) calculations further support the result that the maximum deintercalation rate of Mg atoms is about 78% while maintaining the hexagonal layer structure of boron. This research solves the problems of low Mg atom deintercalation rate and hexagonal boron structure destruction when using the precursor MgB to produce borophene nanosheets, which is of great significance for large-scale novel preparation and application of borophene nanosheets.
以I作为氧化剂，CHCN作为反应介质，在氮气保护下，将MgB在CHCN和HCl的混合溶液中氧化14天，随后在CHCN中超声剥离2小时，制备出化学计量比为MgB的少层缺镁硼烯纳米片（FBN）。所制备的FBN具有二维片状形态，它们显示出清晰的干涉条纹，其面间距为0.251nm，对应于菱形硼的(208)平面。在保持MgB的六边形硼网络的同时，FBN的平均厚度约为4.14nm（四个单层硼烯），横向尺寸为500nm，最大Mg脱嵌率可达78%。反应体系的酸度起着重要作用；HCl反应体系不仅促进了I对MgB的氧化，还提高了Mg原子的脱嵌率。HCl对Mg原子层的蚀刻、I氧化导致硼层负电荷减少以及HCl环境中CHCN水解产生的CHCOOH对Mg的螯合作用导致了Mg原子的高脱嵌率。密度泛函理论（DFT）计算进一步支持了在保持硼的六边形层结构的同时，Mg原子的最大脱嵌率约为78%这一结果。本研究解决了以前体MgB制备硼烯纳米片时Mg原子脱嵌率低和六边形硼结构破坏的问题，这对硼烯纳米片的大规模新颖制备和应用具有重要意义。
