铜基贵金属核壳纳米结构的调控及其电催化CO2还原反应的研究

The tailoring of the lattice strain effect between core and shell regions in core-shell nanomaterials for the modification of electronic structure of shell components is an effective way to enhance their catalytic performance. This project aims at developing a delloying process for the synthesis of Cu-based core-shell nanostructures of noble metals, and would like to make use of the formation of the alloy shell and dealloying to regulate the lattice strain effect of noble metal in shells. This may locate the d-band center of the noble metals at an optimal location for efficiently catalyzing the reduction of CO2. The synthetic strategy involves the preparation of Cu seed particles and subsequent replacement reaction with noble metal precursors to generate core-shell nanoparticles with a Cu core and an alloy Cu-M (M = Au, Ag, Pd) shell, labeled as Cu@Cu-M. Then a delloying process would be applied to partially remove the Cu from the alloy shell, producing a series of core-shell nanostructures with different Cu content in the alloy shell, labeled as Cu@Cu-M-d. The lattice strain effect in as-prepared core-shell nanostructures before and after delloying process will be characterized in detail by X-ray photoelectron spectroscopy (XPS) and aberration-corrected transmission electron microscopy (TEM), and the influence of the formation of alloy shell and dealloying on the lattice strain effect will also be revealed. Finally, we will evaluate the catalytic performance of the Cu-based nanostructures for the CO2 reduction, and construct the relationship between the catalytic behavior and lattice strain effect. The research output of this project would provide a promising approach to the design of highly efficient electrocatalysts for the CO2 reduction.

通过调控核壳结构纳米材料壳层晶格应变修饰壳层组分的电子结构是提升其催化性能的重要方式。本项目拟发展一种通过部分去合金处理制备Cu基贵金属核壳结构纳米颗粒的技术，利用核壳结构合金壳形成及去合金过程对壳层贵金属晶格应变进行调控，使其d轨道密度态中心达到最优位置，进而提升其电催化CO2还原为CO的性能。合成策略是首先采用预先合成的Cu种子颗粒与贵金属M(M = Au、Ag和Pd)前驱体进行电置换反应，将其表层合金化，得到以Cu为核Cu-M合金为壳的核壳型Cu@Cu-M纳米颗粒；然后对其进行不同程度去合金处理，得到壳层中具有不同铜含量的去合金核壳型Cu@Cu-M-d纳米颗粒。通过双球差校正透射电镜和X-射线光电子能谱对去合金前后壳层贵金属晶格应变效应进行表征，归纳出合金壳形成和去合金过程对壳层贵金属晶格应变的影响，通过研究上述纳米颗粒电催化CO2还原的性能，揭示晶格应变与催化性能的关系。

青年基金项目《铜基贵金属核壳纳米结构的调控及其电催化二氧化碳还原反应的性能评估》以铜基纳米材料作为出发点，对CuPd纳米材料的尺寸、形貌、结构和表面组成进行了设计与优化，提升了其在电催化CO2还原中的催化性能。研究中，对各催化剂进行了详细的表征，结合电催化属性和密度泛函理论计算，探究了这些纳米结构催化剂电催化CO2的反应机制，揭示了在电催化CO2还原为CO的反应中，催化活性位点需要更好地平衡中间产物COOH*的吸附和CO*的脱附，以有助于CO的高效生产。除了应用于电催化CO2反应，所制备的催化剂也能高效地应用于环境中有害物质的催化氧化（苯的催化氧化），进一步说明了所制备催化剂在环境清洁和修复领域的潜在应用。另外，基于上述研究中催化剂的调控，研究中也尝试对其它种类的催化剂表面进行了修饰（如Au纳米团簇，Au@Pd核壳颗粒），这些催化剂在电催化CO2反应和乙醇燃料电池的阳极反应中表现出较好的催化性能。项目执行期间发表SCI论文13篇，其中，1篇发表于材料旗舰期刊Matter，1篇发表于国际知名化学期刊Angew. Chem. Int. Ed.，1篇发表于Cell子刊Cell Rep. Phys. Sci.。