纳米阵列负载多酚基金属配合物纳米薄膜的可控合成及其电还原活性物种研究

To fully understand the active species of the electrocatalysts is important yet difficult for developing new electrocatalysts with higher catalytic efficiency. The reason is because electrocatalysis is actually an interfacial reaction. Only the surface of the electrocatalysts with the thickness of only several nanometers can be transformed to the active species. However, the structure information of the active species is always covered by its bulk information because of the ultrathin thickness. As a result, it is necessary to fabricate a self-supported nanofilm electrocatalyst as the material for the identification of their real active species..Herein, we demonstrate the assembly of ultrathin polyphenol-metal complex nanofilm as the model materials for the investigation of the transformation of electrocatalysts under strong cathodic potential, and identifying their active species by choosing electrochemical CO2 reduction as the model reaction. The ultrathin polyphenol-metal complex nanofilm is fabricated through the coordination of metal cations with the polyphenols at room temperature and appropriate pH value. Since the polyphenols are rich in the adjacent oxhydryls, they can couple with the metal ions easily to form the assembly complex film on the current collector with controllable film thickness. The suitable addition of the small molecules with heteroatoms as the second ligand can effectively alter the structure of the complexes. By testing the performance of the electrochemical CO2 reduction of the polyphenol-metal complexes, the effects of the film thickness and the ligand structure on the electrocatalytic activity and selectivity are demonstrated. In addition, combining the results of ex situ and in situ characterizations, as well as the theoretical calculations, we will understand the detailed transformation of the polyphenol-metal complex during the tests, the influence of the ligand structure on the active species, and the relationship between the different active species and their performances of electrochemical CO2 reduction. Our work will not only offer a model material and a guideline for probing the transformation processes and investigating the active species of complex electrocatalysts, but also lay a theoretical foundation for designing the novel electrocatalysts with better performances.

深入认识电催化材料的活性物种是设计高效催化剂的关键。而目前对于电催化材料的活性物种的指认仍然比较困难，其原因在于电催化反应的本质是界面反应，只有催化材料表面几个纳米的薄层才能够转化为活性物种并催化电极反应的进行，而这一薄层的结构信息却往往被材料的本体信息所掩盖。因此，十分有必要设计合成导电基底上负载的纳米薄膜作为模型材料，并揭示其在电催化过程中的物质转化规律及其活性物种。.本项目拟将富含邻位酚羟基的多酚类化合物和金属阳离子在导电基底上直接合成厚度可控、配体结构可调的多酚基金属配合物薄膜作为模型材料，以电催化CO2还原为模型反应，通过对其进行电催化性能测试，并结合非原位、原位表征手段与结构模拟，阐明配合物在电还原过程中的物质演化规律并指认活性物种，研究配体结构对催化活性物种的影响，揭示活性物种与电催化CO2还原活性及产物选择性之间的关联规律，为设计合成新型高效电还原催化剂提供理论依据。

深入认识电极材料在电催化过程中的结构演化并指认其催化活性物种是精准设计高效电催化剂的关键。本项目利用简单的配位组装，合成了厚度可控的鞣酸-金属配合物薄膜，并利用多种电化学原位光谱技术，结合理论模拟和实验结果，揭示了鞣酸-金属配合物薄膜在电催化CO2还原反应过程中的不同电催化条件（如通入气体、施加电位等）会导致不同的结构转化，所产生的不同催化活性物种进而导致产物选择性的变化。而在电解水析氢反应过程中，揭示合金电极材料中的部分组分也可能发生氧化性溶出，并且阴离子空位在反应过程中会诱导表面生成氢氧化物。在电解水析氧的强氧化条件下，揭示金属化合物和杂原子掺杂的碳材料中的非金属组分都会发生氧化并以高价含氧酸盐的形式溶出，剩余组分则会发生原位氧化形成析氧活性位点。在本项目的资助下，申请人以第一作者或通讯作者在Nat. Commun.，Angew. Chem.（4篇），J. Am. Chem. Soc.，Chem，Energy Environ. Sci.，ACS Energy Lett.，Cell Rep. Phys. Sci. （2篇），Sci. China Mater.，Rare Metals，STAR Protocols，Chem. Eng. J.发表SCI论文15篇。其中1篇入选Angew. Chem.热点论文，1篇入选Angew. Chem. VIP论文，3篇入选ESI高被引论文。培养硕士毕业生3人。本项目不仅为研究电极材料在电催化过程中的结构演化和反应机理提供了新的认识，也为设计开发高效电催化材料提供理论依据和科学指导。