多齿含氮金属有机配合物电催化制氢研究

Hydrogen is one of most attractive substitute due to its high-energy contents and water as the byproduct of combustion. The conversion between carbon-free energy sources,especially water and hydrogen,represents one of the most fascinating pathways in future for clean energy conversion and storage. However, water splitting for hydrogen evolution is rather difficult without a catalyst. How to obtain such catalysts that can not only realize water oxidation but proton reduction, but made of earth-abundant metals and less expensive materials? The development of electro-catalysts for proton reduction to hydrogen is meaningful but changenable.The performances of catalysts, such as overpotential, efficiencies, stability, even mechanism can be evaluated by electrochemical methods. To this end, the project aims to synthesize a series of complexes containing N-donor ligands, such as Cu3(L1')3 (L1' = 1-[(2-carboxymethyl) benzene]-3-[benzothiazole]triazenide ion), and evaluate the performances and study the mechanism of catalysts for hydrogen production according to their electrochemical properties. Hopefully, the key factors for the efficiency of hydrogen production,in particular, the nature of electro-catalytic intermediates, the properties of the ligands, as well as the solubility of metal complexes in water，will be determined. Cyclic voltammetry, chronoamperometry as well as photo-electrochemical techniques such as thin-film cells will be used to evaluate the turnover frenquency (TOF) and turnover number (TON) of the catalysts for proton reduction.In this connection, by tuning the stuctures of the triazenides and metal complexes,the overpotential for hydrogen reduction will be decreased, and the catalytic activity and the efficiency of hydrogen production will be improved. The progress of the project is expected to establish a new system for electro-catalytic hydrogen generation by affordable yet efficient organometallic complexes containing N-donor ligands.

氢气能量密度高，且燃烧产物只有水，可挑起解决能源和环境问题的重担。由于其利用非碳能源-水，循环制氢成为众多科学家关注的焦点。而水的分解势必需要催化剂，如何获得廉价而又稳定的催化剂，既能实现水中氧的氧化又实现氢的还原，进而得到氢气和氧气？研究该催化剂快捷、有效的方法是通过电化学技术探讨其电催化性能，并依据过电势以及电催化制氢效率进而实现其在其它装置中的应用。因此，本项目拟合成多齿含氮金属有机配合物（如，Cu3(L1')3，L1'=1-[(2-羧甲基)苯]-3-[苯并噻唑]三氮烯阴离子）并表征其分子结构，研究其光电化学性质，探讨其电催化制氢的性能和机理，寻找相关影响因素，提出优化催化剂分子结构的方案，降低氢还原过电势，提高催化剂催化制氢的效率和稳定性。本项目对多氮金属有机配合物在水中电催化制氢技术的发展有重要学术意义和经济价值。

水是地球上最丰富的资源，通过电解水将能量以化学键的形式储存在氢气和氧气中是解决能源储存问题的一种理想而有效的途径。然而水分解过电势高，直接电解效率低。自然界中绿色植物体内的酶能够高效催化水分解，但这类酶在非生物环境中会失去活性。因此，模拟酶的活性结构设计合成过渡金属配合物用于电催化水的裂解具有重要意义。.1. 为了解决目前大多数均相催化剂普遍存在的水溶性差、催化过电势高、效率低等问题，课题从过渡金属配合物的配体修饰、中心金属选择以及配合物空间位阻三个角度出发，研究了四个系列共九种过渡金属配合物电催化水分解的活性及规律： .①探究了三个具有相同配体的过渡金属配合物Co(bpbH2)Cl2 1、Ni(bpbH2)Cl2 2 和Cu(bpbH2)Cl2 3电催化水的裂解的活性。在相同过电势下，电催化水的还原的效率顺序为 1＞2＞3。.②探究了三个胺基二苯酚配合物FeCl[tBu,OMeBPDA] 4、FeCl[Cl,ClBPDA] 5和CuCl[Cl,ClBPDA] 6 电催化水的裂解的活性。结果表明，配体相同时，铜配合物的活性高于铁的。.③在配合物4、5和6的基础上，设计合成了胺基单苯酚配合物CuCl[tBu,OMePDA] 7和CuCl[tBu,OMePDA] 8，降低了中心金属的空间位阻。7、8同时具有电催化水氧化和水还原的活性。.④综合考虑水溶性及中心金属空间位阻的因素，设计合成了Cyclen配合物[FeCyclen(Cl)2]Cl 9。该配合物在强碱性溶液中具有良好的电催化水氧化的活性。.2．另一方面，课题研究以有机金属配合物前驱体为反应物，合成高效异相催化剂。.①通过一步电沉积法，在基底上合成形貌可控、组成不同的席夫碱金属配合物。研究了电沉积过程的反应机理和成核过程，探索了不同结构沉积物电解水的活性。该方法可以有效、简便地合成电解水催化剂，拓宽了席夫碱金属配合物作为异相催化剂的应用。.②通过简单热解方法合成的钯-碳纳米管同时具备优异的析氢和氧还原反应催化活性。研究表明钯纳米颗粒为碳纳米管表面提供了高效的活性位点，增加了其表面缺陷，增大了其电化学活性面积，从而提高了其电催化性能。通过控制产物中钯的含量可以有效调节其电催化性能。该方法为一步合成低贵金属含量的双功能高效催化剂提供了借鉴的思路。