纳米晶纤维素/石墨烯复合材料应用于CO2催化转化的研究

Cellulose NanoCrystals (CNC) have attracted significant attention because they are renewable, naturally abundant, and easy to be modified and be dispersed in solvent. Due to abundance of hydroxyl-groups on the surface of CNC, reactive CNC can be modified with various chemical groups to accomplish expected surface modification (such as silylation), which could successfully functionalize the CNC. While, graphene (G) is a two-dimensional atomic crystal with high theoretical surface area, strong adsorption of the surface, excellent electronic conductivity, high chemical and thermal stability. When combined CNC with G, the composite material (CNC/G) is expected to fabricate a new type of the catalyst or catalyst support materials with high catalytic efficiency. Graphene is easy to be aggregated and difficult to be modified, however CNC are easy to be chemical modified and have a good colloidal dispersion. More importantly, graphene can improve the stability and conductive performances of CNC. Based on these, I propose here the investigation of the mechanism of the inducible synergism on the new interface formed by interaction between CNC and graphene, or say, the mechanism of the graphene is functionalized with the hydroxyl-groups on the surface of CNC. A hypothesis of the new interface can induce to produce new (or enhance) active sites (such as wrinkle, defect and catalyst load) and enhance the coupled ability between supports and active sties was suggested. The experiments of the catalysis for CO2 conversion to obtain the relationships between the performances (such as catalytic activity) of both the CNC/G and supported catalysts and the factors of the structures and the different active sites of the catalysts will be carried out to validate the hypothesis, which is based on the fact that the activity of catalyst will be significantly enhanced when the catalyst confined within the carbon nanotube channels due to the effect of confinement. In addition, graphene with carbon vacancy and defects displayed a higher catalytic activity than that on a defect free graphene. To clarify the mechanism of the inducible synergism on interface, it will be carried out for the comparative study of the relationships between the performances of CNC/G and supported catalysts and the factors of the compositions and the structure, the morphology and the stability and the uniformity range of CNC/G. According to the mechanism illustrated, new green, biomass based heterogeneous catalysts will be fabricated, and new theory for inducible synergism will be expected, too.

纳米晶纤维素具有生物质原料丰富、表面羟基多、易化学修饰、易溶剂分散等特征；而石墨烯具有强的表面吸附性、高的化学和热稳定性以及优异的导电导热性等。二者的可控组装复合有望制备出新型高效催化剂或催化剂载体材料，并具有新颖结构。纳米晶纤维素能克服石墨烯易于自身团聚和不易被修饰的缺点，提高其比表面积和分散能力；而石墨烯则能提高纳米晶纤维素的稳定性和传导性能，本项目基于上述事实和前期工作基础提出假说：石墨烯的褶皱和缺陷与纳米晶纤维素羟基界面能诱导提高催化活性和增强活性位与载体的结合力。通过对纳米晶纤维素表面化学修饰和石墨烯褶皱、缺陷的控制来提高催化剂负载量、稳定性和活性位的分散度，并应用于CO2催化转化反应来探究催化反应机理、活性中心本质、催化剂的构效关系以及纳米晶纤维素与石墨烯的诱导协同效应。纳米晶纤维素/石墨烯体系研究假说的印证有利于制造新型绿色、可持续、生物质基高效非均相催化剂材料。

项目的背景：CO2 的减排问题是当今人类社会亟待解决的问题和当前科学研究的热点之一。开发和设计新型高效非均相催化剂材料是实现CO2催化转化为高附加值精细化学品的一条有效途径。.主要研究内容：.(1).制备系列高导热石墨烯/纤维素复合膜材料，并在此基础上进一步热处理转化为多孔石墨烯基炭（G-aC）新材料；.(2).系列石墨烯基负载型催化剂和多孔石墨烯/分子筛复合材料。主要包括石墨烯负载纳米金属钯、金等（Pd@CNC/G，Au@CNC/G）, 和系列多孔分子筛/石墨烯（ZSM-5/G）复合材料；.(3).理论方面，通过深入研究石墨烯基复合材料作为电极材料或催化剂或者催化剂载体在反应过程中的若干关键因素（复合材料的尺寸及形貌、孔结构、活性位化学微环境等）对活性和选择性的影响，揭示了石墨烯基复合材料微观结构的变化规律以及电解液与活性位之间的作用机制。.重要结果、关键数据：纳米纤维素改性石墨烯后，制得高质量的导热、导电薄膜及超级电容器电极材料；金属、金属氧化物纳米颗粒修饰石墨烯后，可以制得高效异相催化剂，应用于CO2催化转化、绿色有机合成等领域。发表SCI 收录期刊论文11 篇，其中标注受本项目资助的6篇，影响因子大于8.0以上的科研论文5 篇；申请中国发明专利5 项，授权3 项，合作撰写专著中一个章节；在该项目资助下，项目负责人还获得中国科学院山西煤化所“海外优秀青年”人才项目1项；中央高校基本科研业务费项目1项；广东省“珠江人才计划”引进创新创业团队核心成员；培养研究生4名，参加并组织国内、外相关学术会议。.科学意义：通过对纳米晶纤维素表面化学修饰和石墨烯褶皱、缺陷的控制以及负载型复合材料催化剂的设计，考察所制备复合材料作为催化剂载体（或催化剂）的性能与活性位点分散度及贡献机制分析以及表面性质等因素的内在关系。纳米晶纤维素/石墨烯体系研究有利于制造新型绿色、可持续、生物质基高效非均相催化剂材料。