硫化钴改性石墨炔构建S型异质结高效光催化产氢

石墨炔(GDY,g-C_nH_2n-2)作为一种新型的由sp和sp2杂化的碳原子构成的二维碳材料,因其独特的纳米级孔隙、二维层状共轭骨架结构及半导体性质等特性,使之在能源、电化学、光催化、光学、电子学等诸多领域具有显著优势.它作为一种具有良好的层状结构的新型碳材料,其可调节的电子结构弥补了石墨烯无明显带隙的缺点,有望在光催化分解水领域展现出广阔的应用前景.本文报道了以CuI粉末为催化剂制备石墨炔的新方法,并对其进行改性后制备了Co₉S₈-GDY-CuI新型复合材料;即通过有机合成法和水热法将GDY-CuI片层材料与Co₉S₈纳米颗粒复合,合理构建了S型异质结,展现出良好的光催化活性.石墨炔的层状结构有利于Co₉S₈纳米粒子的分散,能够有效避免粒子聚集,从而暴露出更多的活性位点.石墨炔独特的电子转移特性使得它与染料分子之间的相互作用和键合都能表现出良好的电子转移特性.因此,制备的Co₉S₈-GDY-CuI在染料敏化体系中的产氢活性达到了1411.82μmolg^-1h^-1,是纯石墨炔的10.29倍.通过表征技术深入研究了该复合材料产氢活性提高的内在原因.拉曼光谱研究结果表明材料中存在炔基键,X射线光电子能谱中碳拟合峰以C-C(sp2)和C-C(sp)的形式存在,且两者之间的峰面积之比约为1:2,该结果与理论值吻合.红外光谱结果表明,纯石墨炔和复合材料中存在C≡C.结合紫外可见漫反射和莫特-肖特基表征结果对材料的能带结构进行了深入分析并且提出了该反应的可能机理.结果表明,Co₉S₈-GDY-CuI样品之间形成了双S型异质结,有效地加速了电子的分离和转移.S型异质结的存在有利于提高材料内部的电荷分离效率,保留了更为有效的氧化还原电位,更有利于该材料光催化分解水反应的进行.此外,复合材料中Co₉S₈纳米粒子的引入提高了Co₉S₈-GDY-CuI对可见光的吸收能力,增强了对于可见光的利用率.光致发光光谱和电化学测试结果进一步证明了复合材料中光生电子-空穴对的复合被有效抑制,是Co₉S₈-GDY-CuI材料产氢活性得以提高的内在原因之一.上述研究表明,Co₉S₈-GDY-CuI之间异质结的构建为材料光催化反应的进行提供了一条有效的电子转移路径.本文为石墨炔材料在光催化分解水制氢相关领域提供了一个可借鉴的新思路.

Efficient photocatalytic hydrogen evolution over graphdiyne boosted with a cobalt sulfide formed S-scheme heterojunction

Graphdiyne (GDY, g-CnH2n-2), a novel two-dimensional carbon hybrid material, has attracted signifi-cant attention owing to its unique and excellent properties. As a new type of carbon material, GDY has a layered structure and can be used in the field of photocatalytic water splitting. Therefore, herein, new progress in the preparation of graphene using CuI powder as a catalytic material and the combination of a facile hydrothermal method to prepare a new composite material, Co9S8-GDY-CuI, is reported. The hydrogen production activity of Co9S8-GDY-CuI in the sensitization system reached 1411.82 μmol g-1 h-1, which is 10.29 times that of pure GDY. A series of characteri-zation techniques were used to provide evidence for the successful preparation of the material and its superior photocatalytic activity. Raman spectroscopy showed that the material contains acety-lenic bonds, and the X-ray photoelectron spectroscopy carbon fitting peaks indicated the presence of C-C(sp2) and C-C(sp), further demonstrating that GDY was successfully prepared. A possible reaction mechanism was proposed by making use of UV-visible diffuse reflectance and Mott-Schottky analyses. The results showed that a double S-scheme heterojunction was constructed between the samples, which effectively accelerated the separation and transfer of electrons. In addi-tion, the introduction of Co9S8 nanoparticles greatly improved the visible light absorption capacity of Co9S8-GDY-CuI. Photoluminescence spectroscopy and related electrochemical characterization further proved that recombination of the electron-hole pairs in the composite material was effec-tively suppressed.