甲烷二氧化碳重整镍基催化剂的结构设计与催化作用机制研究

Carbon dioxide (CO2) reforming of methane (CH4) has received increasing attention for simultaneously converting two potent greenhouse gases into useful synthesis gas (H2/CO). The prime bottleneck for industrialization of this technology lies in the catalyst. Ni-based catalysts, the most promising candidates, always suffer from rapid deactivation due to carbon deposition. To solve these problems, it is crucial to synthesize the catalysts in a controllable way and uncover the in-depth activation mechanism and reaction pathways. In this proposed work, the key structural parameters of the catalysts, the exposing planes and particle size of Ni nanoparticles, will be designed at surface and interface levels. Specifically, catalysts with selectively exposing planes of Ni(111) will be configured with the aid of special metal-oxide interfaces by introducing the nano oxides with controllable exposing planes or nanocomposite oxides with tunable electronic structures. Catalysts with metals of small size (< 7 nm) will be configured by anchoring Ni nanoparticles on the functionalized surfaces of nanostructured or doped supports. In-situ infrared (IR), in-situ thermogravimetric analysis (TG), and in-situ EXAFS (extended X-ray absorption fine structure) techniques will be employed as in-situ and dynamic characterizations to investigate the catalytic reaction processes. Theory simulations based on density functional theory (DFT) calculations will be coupled with experimental investigations to understand the structure-activity relationships. The ultimate goal is to comprehend the formation mechanism of the surface and interface structures of the catalysts and how these factors manipulate the catalytic activity. The outcome of the present work is expected to shed light on the catalysis mechanism of CO2 reforming of CH4 and promote the synthesis of highly efficient Ni-based catalysts. Therefore, this unique and creative work is of great significance in both fundamental science and industrial applications.

CH4-CO2重整技术因可将两大温室气体转化为合成气而备受关注，其工业化瓶颈在于缺乏实用的催化剂。最具前景的Ni基催化剂易因表面积碳而失活，急需对催化剂结构的可控设计及催化作用机制进行研究。本项目从催化剂的表面和界面结构入手，针对Ni基催化剂最关键的金属暴露晶面和粒子尺度结构进行设计：通过引入暴露晶面可控的纳米氧化物或电子结构可调的复合氧化物，利用金属-氧化物界面构建选择性暴露Ni(111)晶面的催化剂；通过调变载体的尺度形貌或对载体表面进行原子掺杂，利用化学锚定构建Ni粒子尺度<7 nm的催化剂。借助原位红外、原位热重和原位EXAFS技术对催化反应过程在线表征，结合密度泛函理论计算对构-效关系深入探索，理解催化剂表界面结构的形成机理及其对催化反应性能的调变机制。研究结果将加深对CH4-CO2重整催化反应机理的认识，促进新型高效Ni基催化剂的设计制备，因此，项目具有重要的科学和应用价值。

CH4-CO2重整技术可将两大温室气体转化为高附加值的合成气，作为典型的负排放技术，在“碳中和”战略中具有重要意义。该技术尚未工业化，其主要瓶颈在于广泛研究的Ni基催化剂易因表面积碳而失活。项目采用纳米合成与表面功能化相结合的策略，构建了超小粒径、表面功能化和界面调控的高效Ni基催化剂；通过实验表征与理论计算相结合的策略，揭示了影响积碳与稳定性的主要结构参数。主要取得以下重要结果：1）借助阴阳离子双水解和原位生长还原等新技术，一步法制得金属粒子为2.0-4.0 nm的Ni基催化剂，制得的催化剂展现优异的重整催化性能。结构表征揭示小的金属尺度是催化剂重整性能提升的关键因素；2）基于LaAlO3钙钛矿材料、纳米Al2O3和不同晶相ZrO2等特殊载体，构筑了表界面结构各异的Ni基重整催化剂，确认了金属粒径、碱性位和氧空位是改善催化剂抗积碳性能的关键结构参数；3）通过纳米复合和光-热耦合等策略，分别在CO2加氢制甲烷和甲醇等相关研究方向进行了延伸探索，开辟了CO2催化转化性能提升的新路径，揭示了通过界面促进CO2分子活化转化的新原理。以上研究结果为CO2转化催化剂的研制提供了新思路，为CO2活化转化机理的认识提供了新原理，将对我国温室气体减排和清洁能源生产等领域带来积极影响。项目已在Joule、Angew. Chem. Int. Ed.和Ind. Eng. Chem. Res.等期刊发表SCI论文18篇，其中高被引论文2篇，期刊封面1篇；参加学术会议13次，做特邀报告7次。同时，项目负责人在CO2催化转化方向应邀担任国际期刊客座编辑，分别在Catal. Today和Greenh. Gases出版专辑1期。