准二维分子筛/石墨烯限域电催化还原CO2

Utilization of carbon dioxide as a kind of carbon resources is an important strategic research topic in face of human being. The electrochemical reduction of carbon dioxide is an emerging technology, which has the advantage of being performed under ambient temperature and pressure. The key issue is how to design a new type of electrocatalyst with high efficiency through precisely designing and tuning the structure and the active electrocatalytic sites of catalyst materials as well as environmental conditions. Based on my own research experiences in zeolites and graphene fields, I got an idea: a new electrochemical platform composed of zeolite and graphene nanocomposites can be built. Zeolites show strong confinement effects but they are usually insulating, while graphene has extraordinary electrical conductivity but the strong π-π stacking interactions between graphene microsheets can lead to serious aggregation and restacking. This project intends to fabricate a series of ultrathin lamellae quasi-two-dimensional zeolites/graphene nanohybrids, test their performances in electro-reduction of carbon dioxide, identify the active electrocatalytic sites, and reveal the reaction mechanism of the electrocatalysis. We will answer a fundamental question of designing, fabricating and identifying the active electrocatalytic sites of confined electrocatalysis in quasi-two-dimensional zeolites/graphene nanohybrids. Through the control of the graphene defects and surface functional group, surfactant compositions, the ratio of the precursors and the environmental parameters, controllable quasi-two-dimensional growth of zeolites (such as ZSM-5) onto graphene substrate will be promoted while the 3D growth will be prohibited. Moreover, metal nanoclusters will be constructed in the nanohybrids to improve the catalytic performances. We will use isotopic tracer method and in-situ spectroscopy approaches to identify the interfacial active electrocatalytic sites and investigate the mechanism of confined electro-reduction of CO2. This project covers interdisciplinary research, and it could probably supply a new route for confined catalysis and utilization of carbon resources.

二氧化碳的资源化利用是人类面临的一项重要课题。还原CO2的电催化法具有条件温和环境友好的优点而受关注，其关键是如何精确设计调控催化活性位匹配环境而创制高效催化剂。本人据分子筛和石墨烯研究基础提出问题：分子筛的限域效应强但不导电，石墨烯导电性好但易团聚，二者复合有望优势互补，构建电催化新平台。本项目将研究：准二维的分子筛/石墨烯超薄催化材料的构筑、CO2电化学还原性能以及催化活性位和机制分析，拟解决如何调制鉴别准二维分子筛/石墨烯“限域电催化”的活性位结构的关键科学问题。通过调控石墨烯缺陷和表面基团、表面活性剂的成分、原料配比及环境参数，促进石墨烯基底上分子筛（如ZSM-5）的二维生长，并限域负载金属（如铜）纳米簇。通过同位素示踪和原位光谱等多种分析手段，鉴别分子筛/石墨烯/金属簇的界面活性位，阐明限域电催化还原CO2的机制。本项目立足于学科交叉，有望提供一种限域催化和碳资源利用的新途径。

二氧化碳的资源化利用是人类面临的一项重要课题。还原CO2的电催化法具有条件温和环境友好的优点而受关注，其关键是如何精确设计调控催化活性位匹配环境而创制高效催化剂。据申请人分子筛和石墨烯研究基础提出：（1）在石墨烯基底上原位生长高度取向的准二维ZSM-5分子筛，系统研究了石墨烯基底上分子筛前驱物的原位凝胶化、水热晶化、烧结晶化过程。通过控制石墨烯的尺寸、缺陷和表面化学基团，并调变表面活性剂的种类和浓度、原料的比例以及环境参数，抑制分子筛三维生长，促进二维生长。分析了石墨烯基底上分子筛的准二维生长机制。（2）设计合成了系列单原子分散过渡金属（Fe, Co, Ni, Cu等）/石墨烯复合材料，多孔石墨烯/分子筛复合材料和碳纤维/石墨烯复合材料。考察了所的材料分别在ORR，OER，CO2RR和固体酸催化反应中的性能。（3）综合运用同步辐射X射线吸收谱，HAADF-STEM，EELS，XPS和HRTEM揭示了上述催化材料ORR，CO2RR和OER的反应机理和活性位本质。重要结果及关键数据：（1）系列ZSM-5/G催化剂在系列强酸催化的有机反应中也表现了高的活性比相应的传统ZSM-5催化剂，实现了水介质清洁有机合成和原子经济反应，为未来开发石墨烯基催化剂及固体酸催化剂的工业应用提供了实验依据。（2）Fe/G 催化剂在ORR反应中表现了良好的综合性能。该催化剂能重复使用10000次活性基本保持不变。Fe/G-carbon nanotube催化剂在碱性水溶液为电解液的CO2RR制CO反应中表现出> 95%的法拉第效率，连续测试24小时，催化剂活性不降低。Co3O4-Co/石墨烯复合材料在ORR反应和锌-空气电池中均表现出优异的性能。本项目立足于学科交叉，有望提供一种碳资源利用的新途径。由碳纤维和石墨烯构成的钢筋混凝土结构表现出优异的机械和电化学性能，有望在未来新能源汽车上得到广泛应用。