杂原子掺杂的多尺度碳纳米材料的结构设计与CO2电催化还原机制研究

Electrocatalytic reduction of CO2 into chemical fuels or produces, represents a potentially strategy for replacing fossil feedstocks and dealing with increasing CO2 emissions and their dangerous effects of global warming. However, one of the major drawbacks of electrochemical CO2 reduction in aqueous solution is the high overpotential required to achieve substantial reaction rates and selectivity. Therefore, the development of the efficient catalysts for electroreduction CO2 has become a major research topic. So far, considerable researches have focused on metal or metal complex for CO2 electroreduction, but heteroatom-doped carbon nanomaterials as electrocatalysts in CO2 conversion have received little attention. And there is no clear consensus on the understanding the mechanism of CO2 electrocatalytic reduction reaction. Herein, conducting polymer will be employed as precursor to develop heteroatom-doped carbon nanomaterials that feature well-defined structures and composition, which can be controlled by combining the polymerization, doping, with etching and carbonization. The relationship between micro/nanostructures, electron structures of electrocatalysts and CO2 electrochemical reduction will be studied, and the reduction mechanism will be revealed. It is worth mentioning that the synergized effect of micro/nanostructures, electron structures and surface wettability may be attributed to the improved performances of CO2 electrochemical reduction. The study mentioned here may provide a theoretical and practical guide for designing and developing the low-cost, high selective and efficient electrocatalysts for reduction of CO2.

电催化还原可将CO2转化成燃料或高附加值的化学品，不仅解决温室效应带来的环境问题、还可缓解日益严重的资源枯竭。但是，CO2电催化还原面临的挑战就是活化CO2需要高过电位，这导致CO2还原产物的选择性降低、转化率下降。因此，开发高效的CO2电还原催化剂成为了材料领域的研究热点。目前，CO2电催化剂的研究主要集中的金属及其化合物，而杂原子碳材料的研究不多，且其催化还原机制尚未达成一致。本项目拟以含杂环导电聚合物单体为组装单元，采用氧化、掺杂、刻蚀、碳化等技术开发分子与微观结构可控、含杂原子的多尺度、微纳米结构碳纳米材料；重点研究其作为高效的CO2电化学还原催化剂及其催化机理，特别关注杂原子掺杂的碳电催化剂的纳米效应、电子结构、表面浸润性的“三重”协同效应调控CO2电催化还原的构-效关系。预计本项目的研究成果将对设计、开发廉价、高效的CO2电化学还原催化剂提供理论指导，促进CO2的资源化化利用。

电催化还原二氧化碳（CO2RR）为有价值的化学品和燃料，对可再生能源的存储和缓解气候变化都至关重要。但是，由于CO2分子中高度稳定的化学键，以及水体系下析氢的竞争反应，CO2RR面临产品选择性差、转化率低等重大障碍。因此，开发高效催化剂是CO2RR研究的重点和难点。我们利用导电聚合物主链的杂原子与过渡金属的配位作用，设计和开发了系列杂原子掺杂碳材料以及复合材料。例如，开发了通用的多米诺反应策略，实现了大规模制备单原子锚定的氮掺杂碳纳米片催化剂（M-SA/NC，M包括Fe、Co、Ni、Mn、Mo、Pd及其组合（FeCo、FeNi、FeCoNi））；利用导电聚合物多样的纳米结构，开发了1D/2D结构的氮掺杂碳纳米棒/超薄碳纳米片、氮掺杂碳纳米纤维负载Zn单原子、掺杂和修饰的二硫化钼等催化剂将CO2转化为CO。另外，开发的银锚定的氮掺杂石墨碳泡沫可将CO2转化为乙醇等。通过杂原子与过渡金属的相互作用，调节其电子结构，改善其CO2RR性能；通过改变界面浸润性调控CO2还原产物的组成比例。通过理论计算揭示了N掺杂碳材料中，N原子的种类、配位结合的过渡金属电子结构等对CO2还原中间体形成的影响，为设计和开发高性能CO2RR催化剂提供理论和实验指导。此外，发明了一种超浸润诱导自驱动成膜技术，实现了石墨烯透明薄膜的快速、连续化大面积制备。而且，该石墨烯薄膜的制备技术具有普适性，适用于其他零维、一维和二维纳米材料，可实现多功能薄膜的制备，这为电化学能源和物质转化提供丰富的功能性电极材料。