MOFs复合体系可控热解构筑MoCx@C基复合纳米结构及其协同电催化机制

Development of high-performance, stable and low-cost pH-universal hydrogen evolution electrocatalyst is a major challenge faced by current energy and environmental science. To address this issue, this project intends to organically integrate Fe, Co, Ni-based metal-organic frameworks (MOFs) with different forms of molybdenum compounds via several routes, such as impregnation, vapor deposition, ion exchange and self-assembly in liquid phase. With this target composites being pyrolyzed in hydrogen atmosphere, in order to construct novel MoCx@C-based nanohybrid for electrocatalytic hydrogen evolution reaction (HER). In virtue of the metal-embedded and heteroatom-doped carbon nanotubes or graphenes in situ formed during the carbonization of MOFs acting as both the conductive supports and catalytic fortifiers, the catalytic activity of MoCx is expectedly to be greatly enhanced. By systematically adjusted the synthetic conditions, and combined with the material characterizations and catalytic test, the formation mechanism, phase transformation process, migration and integrate rule of each component in MoCx@C-based nanohybrid, as well as the relationships between the structures and catalytic performance of MoCx@C-based nanohybrid can be fully recognized. Furthermore, an effort will be made to clarify the specific role of each active component and the electrocatalytic synergism between each other and also the different crystal phases of MoCx based on the interfacial structural simulation and theoretical calculations. This research will shed some light on both experimental and theoretical design and synthesis of high-performance MOFs-derived HER hybrid electrocatalysts.

发展可在全pH范围使用的高效、稳定且廉价的电解水制氢催化剂，是当前能源环境科学领域面临的一项重大挑战。本项目拟以铁、钴、镍基金属有机框架（MOFs）材料与不同形式钼的化合物，通过浸渍、气相沉积、离子交换及液相自组装等方式进行有机复合，并于氢气气氛下热解，构筑基于MoCx@C的新型纳米复合结构用作析氢反应的电催化剂。利用MOFs热解所原位生成的内嵌金属型掺杂碳纳米管或石墨烯，同时作为MoCx的导电载体及耦合增强体，以促进MoCx析氢催化性能的进一步提升。通过合成条件的调控，结合材料表征数据及催化性能测试结果，研究MoCx@C基复合结构各活性组分的形成机制、相变过程、迁移复合规律以及催化的构效关系。并对材料复合界面进行结构模拟及理论计算分析，阐明MoCx@C基复合结构中各活性组分及不同晶相MoCx间的协同催化机制，为此类基于MOFs的高效复合型析氢电催化剂的设计合成奠定实验和理论基础。

当前石化能源的日益枯竭以及地球环境的恶化，迫使我们需要开发出规模化的清洁可持续能源。电解水制氢由于其较高的产氢效率以及操作方便，成为目前极具前景的一种解决方案。但电解水阴阳两极仍需要发展出高效且廉价的氢析出反应（HER）和氧析出反应（OER）电催化剂。为此，本项目从钼化合物出发，将其与多孔金属有机框架材料进行有机复合，并以此为前驱物，通过可控热解过程，研制出高效的钼基电催化剂材料。通过本项目的实施，我们成功发展了多种钼化合物与金属有机框架材料复合的有效策略，认识了热解过程中两相物质各自的演化融合过程，为高效钼基电催化剂材料的结构组成优化提供了经验借鉴。对所合成的钼基电催化剂的电催化性能进行了系统表征，结果表明达到10mA/cm2的反应电流时，碱性介质中最佳HER和OER性能的过电位分别仅为37 mV和280 mV。我们进一步通过结合各种结构表征数据和理论计算结果，对钼基电催化剂的优异性能进行了分析，揭示了其各活性单元间的协同催化机制。本项目的成功实施，为基于金属有机框架材料衍生的高效电催化剂材料的构筑奠定了相关实验和理论基础。