氢取代石墨单炔的机械化学合成及其电催化特性

氢取代石墨单炔是一种仅由苯环上的sp~2杂化碳和氢与乙炔基上的sp杂化碳组成具有与石墨炔相似平面网状结构的二维富碳材料。本文以碳化钙和三溴苯为原料,通过机械化学方法合成了氢取代石墨单炔,并通过X射线电子能谱、拉曼光谱、固体核磁共振成像~1H谱和透射电子显微镜加以证实。紫外可见漫反射吸收光谱和电化学测试表明样品为p型半导体,带隙为2.30 eV,在硫酸钠溶液(pH=7)中的析氧起始过电位为0.04 V,在催化产氧和光催化方面具有应用潜力。

Synthesis of Hydrogen Substituted Graphyne through Mechanochemistry and Its Electrocatalytic Properties

Since the successful synthesis of graphdiyne, graphynes have emerged as an active field in carbon materials research.Hydrogen-substituted graphyne, structurally similar to graphynes, is a kind of two-dimensional (2D) carbon-rich material composed of sp²-hybridized carbon and hydrogen from phenyl groups and sp-hybridized carbon from ethynyl linkages.The large pore size in the molecular structure of hydrogen-substituted graphyne aids the diffusion of ions and molecules.In this work, hydrogen-substituted graphyne was synthesized by a facile mechanochemical route.Calcium carbide (CaC₂) was employed as the precursor of sp-hybridized carbon and 1, 3, 5 tribromobenzene (PhBr₃) as that of sp²-hybridized carbon and hydrogen.Hydrogen-substituted graphyne was directly obtained via the cross-coupling reaction performed by ball milling under vacuum and the impurities were removed by dilute nitric acid and benzene.Mechanochemistry is a mature technology for the simple and high-yield synthesis of nanostructured materials.The composition of the as-prepared hydrogen-substituted graphyne was confirmed by Raman and ¹H solid-state nuclear magnetic spectroscopies.Energy-dispersive X-ray (EDX) spectrum and X-ray diffraction (XRD) patterns indicated that the purity and crystallinity of the prepared samples are high, which was further confirmed by the corresponding selected area electron diffraction (SAED) patterns.Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) images illustrated that samples had nanosheet structure with a layer-to-layer distance of 0.35 nm.However, owing to the lack of a substrate, the nanosheets reunite to form irregular microparticles, as shown in the scanning electron microscopy (SEM) images.Twin structure was found in the as-prepared samples, which might be relevant to the mechanochemical process.The samples were used to prepare electrodes for the photoelectrochemical and electrochemical catalytic analysis.The open circuit potential under chopped irradiation of the electrode showed that the as-prepared hydrogen-substituted graphyne was a p-type semiconductor.The band gap was calculated to be 2.30 eV by UV-Vis diffused re?ectance (UV-Vis DRS) spectroscopy.The electrocatalytic properties of the sample were determined using a three-electrode cell in a neutral solution (Na₂SO₄, 0.5 mol·L^?1).The onset overpotential for hydrogen evolution was ?0.17 V; however, the Tafel slope was too large (1088.4 mV·dec^?1), which restricted application in electrocatalytic hydrogen evolution.On the other hand, the overpotential for oxygen evolution reaction was only 0.04 V and the Tafel slope was 70.0 mV·dec^?1, making applications in electrocatalytic oxygen evolution and photocatalysis possible.This strategy opens a new avenue for preparing graphyne with good electrochemical properties using readily available precursors under mild conditions.