【作者】 张博；

【导师】 符秀丽；

【作者基本信息】 北京邮电大学 ， 电子科学与技术， 2021， 博士

【摘要】 随着化石能源的快速消耗导致的能源危机和环境污染问题日趋严重,改善能源体系结构、减少化石能源的消耗是当前亟待解决的关键问题。有效开发利用氢能、风能、太阳能等清洁能源,发展新型电化学转换与储能器件越来越受到研究者们的广泛关注。二维材料,如二硫化钼(MoS2)、Ⅳ-Ⅵ族硫属化合物(MXs)、石墨烯及其衍生物等,由于其独特的微观结构和优异的物理化学性质,已经被证明在电化学催化和储能应用等方面具有巨大的潜力。但是,上述电化学反应过程通常发生在材料的表面,因此在进行催化剂和电极材料的设计时,针对其表面的缺陷设计与性能调控具有十分重要的科学研究意义和工程应用价值。本论文以几种典型二维材料为研究对象,从材料的基平面、边缘的缺陷设计和调控入手,研究了这些材料的催化析氢反应(HER)活性,以及将其作为超级电容器电极材料的电容特性。所取得的创新性研究成果如下:(1)通过原子无序化工程在MoS2的基平面上引入MS2或MS量子点(M=Ge、Sn或Pb),成功激活了其HER活性。相较于纯的MoS2,MS2或MS量子点的引入使得MoS2基平面上的氢吸附吉布斯自由能(△GH)从1.71 eV下降到了 0.50 eV以下,对应的电流密度从10-30 A cm-2提升到了 10-3 A cm-2,表明其HER活性得到极大的提升。当对上述全部模型施加小于2%的拉伸或压缩应变时,这些模型仍然保持了良好的结构稳定性和较高的HER活性(△GH值仍保持在-0.5至0.5 eV区间);尤其是,当在PbS@MoS2模型在施加了 2%的拉伸应变后,其对应的△GH值甚至降到了-0.02 eV,对应的电流密度接近100A cm-2,具有极高的HER活性。(2)研究了点缺陷诱导的单层MXs(M=Ge或Sn,X=S或Se)模型边缘的HER活性。研究表明,具有Ge空位的GeS边缘、具有Se空位的GeSe边缘和具有Sn空位的SnSe边缘的△GH值分别为0.016、0.073 和-0.037 eV,接近于贵金属 Pt 的△GH值(-0.07eV),揭示了其优异的HER活性。当对上述全部模型施加小于2%的拉伸或压缩应变时,这些模型仍然保持了良好的结构稳定性和较高的HER活性(△GH值仍保持在-0.2至0.2 eV区间);尤其是,具有Ge空位的GeS边缘,当在其上施加2%拉伸应变时,其对应的△GH值接近0 eV,具有极高的HER活性。(3)为了提升W2C和类石墨烯结构(包括G、GN、P3N和P2V4N)的HER活性,研究了由W2C和多种类石墨烯结构结合形成的异质结构的HER性能。与纯W2C和类石墨烯相比,这些异质结构均表现出了更高的HER活性。其中P3N@W2C-2异质结构模型的ΔGH值甚至达到了 0.003 eV,具有极高的HER活性。关于电解液pH值对所有模型ΔGH值的影响规律的研究表明:无论在酸性、中性或碱性环境中,由氮原子(N)改性后的石墨烯与W2C组成的异质结构模型具有较多的HER活性位点,它们的△GH值接近0eV,表明N改性能够使这些异质结构在更宽的pH区间内保持较高的HER活性。(4)对于56种3d、4d以及5d过渡金属(TM)掺杂的石墨烯(TM@G)以及TM和空位(Ⅴ)共掺杂的石墨烯(TM@VG)的电容性能进行了研究。结果表明,TM和V的引入能有效提升石墨烯电极的量子电容和表面电荷密度。此外,由不同TM掺杂获得的石墨烯结构在作为超级电容器电极材料时表现出了不同的选择性。获得了在水系、离子液体和有机电解质系统中最适合的石墨烯基电极材料结构模型。如在水系电解质溶液中,Y@G、Ta@VG、Au@VG和Ni@VG结构适合作阳极,Sc@VG、Y@VG、Fe@VG和Zn@VG结构则适合作阴极,而Cu@VG和Re@VG结构适合于对称性超级电容器电极。更多还原

【Abstract】 With the energy crisis and environmental pollution caused by fossil energy consumption becoming more and more serious,improving energy architecture and reducing fossil energy consumption are the key problems that need to be solved urgently.The development and utilization of hydrogen energy,solar energy and other clean energy,and the development of new electrochemical conversion and energy storage devices have been more and more widely concerned.Due to the unique microstructure and excellent physical and chemical properties of 2D materials(MoS2,graphene,graphene,etc.),it has been proved to have great potential in electrochemical catalysis and energy storage applications.However,electrochemical reaction process usually occurs on the surface of the material,so in the process of design of catalyst or electrode material,the design and regulation of defects on its surface has important scientific significance and engineering application value.In this paper,several typical two-dimensional materials are used as research objects.Starting with the defect design and regulation of the base plane and edge of these material.The electrocatalytic hydrogen evolution reaction(HER)activity and the capacitive properties base on these materials are are studied.The innovative research results are as follows:(1)The HER activity of MoS2 was successfully activated by the introduction of MS2 or MS quantum dots(M=Ge/Sn/Pb)on the base plane of MoS2 by atomic disorder engineering.Compared with pure MoS2,the introduction of MS2 or MS on the base plane of MoS2,makes the corresponding HER performance improved.The hydrogen adsorption Gibbs free energy(ΔGH)on the base plane of MoS2 dropped from 1.71 eV to less than 0.50 eV and the current density increased from 10-30 to 10-3 A cm-2.When the less than 2%tensile or compressive strains are applied,these models still maintain good structural stability and high HER activity(the value of △GH remains in the range of-0.5 to 0.5 eV);in particular,the△GH value of the PbS@MoS2 model has even dropped to-0.02 eV after applying a 2%tensile strain,with a current density close to 100 A cm-2.(2)The HER activity of the edge of single-layer MXs(M=Ge/Sn,X=S/Se)models induced by point defects was studied.The results show that the △GH values of GeS edge with Ge vacancy,GeSe edge with Se vacancy and SnSe edge with Sn vacancy are 0.016,0.073 and-0.03 7 eV,respectively,which are close to the △GH value of noble metal Pt(-0.07 eV),showing excellent HER activity.When less than 2%tensile or compressive strain are applied to the above-mentioned models,the models still maintain good structural stability and high HER activity(△GH value remain in the range of-0.2 to 0.2 eV);in particular,the GeS edge with Ge vacancy,when applying a 2%tensile strain,has a △GH value close to 0 eV,with excellent HER activity.(3)In order to improve the HER activity of W2C and graphene-like structures(G,GN,P3N and P2V4N),the HER performance of the heterostructures formed by W2C and graphene-like structures were studied.These heterostructures exhibit higher HER activity than pure W2C and graphene-like structures.Among them,the P3N@W2C-2 model of the △GH value even reached 0.003 eV,with excellent HER activity.On the effect of pH on the △GH value of △GH,the study shows that:whether in acidic,neutral or alkaline environment,the heterostructures consisting of nitrogen atom(N)have more HER active sites,and their △GH value is close to 0 eV,indicating that N modification can keep these heterostructures with high HER performance in wider pH interval.(4)The capacitive properties of 56 kinds graphene-based models,including 3d,4d and 5d transition metals(TM)doped graphene(TM@G),and TM and vacancy(V)co-doped graphene(TM@VG),were studied.The results show that the introduction of TM and V can effectively improve the quantum capacitance and surface charge density of graphene electrodes.In addition,graphene doped by different TM exhibit different selectivity when acting as supercapacitor electrodes.In aqueous electrolyte,Y@G,Ta@VG,Au@VG and Ni@VG structures are suitable for anodes,Sc@VG,Y@VG,Fe@VG and Zn@VG structures are suitable for cathodes,and Cu@VG and Re@VG structures are suitable for symmetric supercapacitor electrodes.更多还原