小尺寸二维单层MXene相Ti3C2的可控制备和氧还原性能研究

It is of highly challenging but desirable to develop nonprecious metal catalysts with efficient and stable performance as an alternative of Pt for the oxygen reduction reaction (ORR) process, particularly for fuel cells. Poor activity or stability, as well as indistinct catalytic site are the main problems the state of the art for nonprecious metal catalysts. MXene phase Ti3C2 is a potential ORR catalyst as a combination of perfect conductivity and stability, but has not been reported as ORR catalyst until now. Single-layer two dimensional Ti3C2 with subsize will be designed and synthesized by a freshly developed cationic surface active agent intercalation method and serve as ORR catalysts in this project. To enhance the ORR activity, transition metal/Ti3C2 composite will also be synthesized and the composition, the microstructure will be optimized. The relationship of nanostructure-composition-ORR performance will be investigated. On the basis of above results, we will propose the ORR catalytic mechanism for Ti3C2. This research will not only develop controllable synthesis method for single-layer, small size Ti3C2, offer scientific support for the design of ORR catalysts, but also expand the applied fields of MXenes.

发展高效、稳定的非贵金属氧还原（ORR）催化剂来取代贵金属催化剂，对于促进燃料电池的广泛应用具有重要的意义。当前研究的非贵金属催化剂主要面临催化活性和稳定性不能满足实际应用需求，催化活性中心存在较大争议等难题。MXene相Ti3C2材料具有稳定性好、电导率高等优点，具有潜在的电催化应用前景，但目前尚未有关于Ti3C2基非贵金属ORR催化剂的报道。本项目将发展一种阳离子表面活性剂插层的方法来可控制备Ti3C2材料，该方法得到的Ti3C2具有小尺寸和二维单层的特点，将极大有利于ORR活性的提高。在此基础上，本项目拟制备过渡金属/Ti3C2复合材料，进一步提高其ORR性能，并系统研究材料的催化性能与其组成、结构的关系，阐明材料ORR催化机制，得到高效Ti3C2基ORR催化剂。本项目的开展将为ORR催化剂的设计与催化机制研究提供科学支撑，同时对拓展Ti3C2材料的制备方法和应用领域也具有重要意义。

首首先探索制备了二维单层MXene相Ti3C并研究了其电催化氧还原性能：通过HF酸刻蚀和TPAOH插层的方法，成功得到了超薄的Ti3C2纳米片材料。Ti3C2纳米片在碱性条件下表现出良好的氧还原催化活性和稳定性。此外，电催化水分解分为阳极的氧析出反应和阴极的氢析出反应。当前该方面研究主要集中于高效电催化剂开发，然而多年来虽有诸多进展，但阳极氧析出反应仍需要较大过电位且得到的氧气附加值较低。因此，项目团队紧扣能源电催化的主题，针对当前电催化水分解过程这一关键问题，提出了“电合成辅助的电催化水分解析氢”策略。即在电解池阳极加入合适的化学品，以化学品的氧化反应取代氧析出反应。该方法不仅显著降低了水分解过程的过电位，且在得到阴极产物高纯氢气的同时可以获得高附加值的阳极产物。该策略还成功的应用到电化学二氧化碳还原领域，获得了阳极阴极同时获得高附加值甲酸的电催化体系。