镍基LDH/rGO衍生类纳米片阵列催化剂的结构调控及其光热CO2加氢应用

On basis of the photothermal effect of nanomaterials, the recently emerged solar-driven CO2 hydrogenation technology has drawn great attentions due to its low-energy consumption and high utilization efficiency for clean solar energy. However, to date, the reaction products are mainly low-value-added C1 compounds (CO and/or CH4) and the catalysts inevitably suffer from carbon-deposition deactivation or unexpected aggregation of nanoparticles during hydrogenation process. Thus, the design of hierarchical structured photothermal catalysts with excellent structural stability and controllable particle size may be a key approach to solve the above problems. In this project, based on the net trap confinement effect of layered double hydroxide (LDH) materials, small-sized and highly dispersed hierarchical structured catalysts were obtained by calcining initially prepared series of Fe, Co and Ce modified LDH/rGO (reduced graphene oxide) precursors with ultrathin LDH nanosheets. The structure-activity relationship and the influence of some parameters including the morphology, particle size, electronic structure and the strong synergistic effect of SMSI on C2+ selectivity together with carbon deposition behavior will be elucidated based on systemic characterizations and catalytic tests. Upon in situ analysis and DFT theory calculations, the catalytic reaction route of solar-driven CO2 hydrogenation would be tentatively proposed after investigating the influence of the incident light wavelength on catalytic activity at a fixed reaction temperature. These results will provide important experimental data and theoretical support for the design of new photothermal catalysts.

基于纳米材料的“光热效应”，光驱动CO2加氢技术既能实现太阳光清洁能源的高效利用，又可大幅降低反应能耗，是制备太阳能燃料的全新手段。然而，目前报道的光热催化剂体系局限于生成低附加值的C1产物，同时，加氢过程中积碳失活和粒子团聚问题难以回避。因此，提出设计结构稳定、粒子尺寸可控的新型多级形貌光热催化剂可能是解决上述问题的关键。本研究首先在还原氧化石墨烯（rGO）表面原位组装系列Fe、Co、Ce修饰的超薄水滑石（LDH）纳米片，进一步调控煅烧还原过程即可在rGO表面限域生成小尺寸、高分散的多级镍基加氢催化剂。通过系统的表征和加氢测试，关联催化剂形貌、粒子尺寸、电子结构和金属-载体强协同效应对C2+选择性及积碳行为的影响规律；深入研究特定温度下不同光波长对上述加氢活性的影响，并结合原位分析和理论计算，尝试提出光热催化CO2加氢路径。项目的开展将为新型光热催化剂的设计提供重要的实验数据和理论支撑。

CO2的高效转化不仅可以在源头上实现减碳，同时可以利用CO2为原料合成各种烃类、甲醇等大宗化学品，应用前景广阔。基于此，我们提出多相催化反应中设计结构稳定、粒子尺寸可控的多级结构纳米催化剂可能是解决上述问题的关键。为提升材料的传热、传质能力，我们在泡沫镍（NF）基质上构建了一系列Co、Ni基超薄水滑石（LDH）纳米片，进一步调控煅烧-还原过程即可获得表面限域的小尺寸、高分散的多级结构加氢催化剂。同时，选择H2、CH4和H2O作为氢源，实现了CO2的多路径加氢转化。特别地，为深入理解光热反应中等离子体共振产生的热电子促进效应，我们直接研究了等离子体外场下高能电子、自由基与材料表面的相互作用，并通过系统的表征和加氢测试，关联催化剂形貌、粒子尺寸、电子结构和金属-载体强协同效应对C1~C4选择性及积碳行为的影响规律。取得的重要结果和意义如下：.①控制合成参数，成功制备多级结构MAl-LDH/NF（M=Ni、Co）及NiMAl-LDH/NF（M=Ru、La、Fe、Ce）前驱体及其衍生催化剂，并探索了等离子体辅助富缺陷型催化剂的制备工艺，拓宽了催化材料的制备范围和应用场景；.②针对CO2加氢，发现了热电子促进效应可显著促进CO2加氢活性（300 oC：CO2转化率>75%）、抗S中毒能力及高能量效率（~10.5%）；.③针对CO2/CH4重整，利用射频等离子体处理形成富空位型Co-MgO-Ov多相界面，大幅提升了液态化学品（甲醇等）选择性（~40%），并联合原位表征和DFT计算初步揭示了等离子体外场下活性粒子与材料的相互作用机制。.当前结果丰富了过渡金属催化剂的制备思路并初步阐明了热电子和等离子体中高能电子在CO2活化、表面重排的关键作用，为CO2的高效利用提供了直接的实验数据与理论支撑。