摘要
近年来,具有可控元素分布的铜基多金属纳米晶作为CO2还原反应(CO2RR)的电催化剂,受到了广泛研究.通过对铜电催化剂进行二次甚至多次的金属元素修饰,能够有效改变其整体d带结构并引起d带中心的位移.这种变化可以影响铜对关键中间体的表面亲和力,从而影响后续的催化途径.除了调整电子结构,形貌工程也成为提高CO2RR电催化性能的有效手段.相对于随机形状的球形颗粒,基于二维纳米片构建的三维多孔结构有利于最大限度地暴露表面原子,为催化过程中产生的关键中间体提供丰富的扩散通道和反应中心.然而,通过设计合成路线构建这种类型的纳米结构是一项技术挑战,传统的分步自组装策略耗时且难以精确控制结构.因此,我们的研究旨在实现高纯度的合成方法,制备这种独特的纳米结构,并精确调控元素组成和电子结构,以探索结构优势与CO2RR电化学性能改善之间的潜在关系,具有重要的应用价值.在此研究中,我们合理设计了钯-铜-银(Pd-Cu-Ag)纳米晶的二维-三维杂化结构,实现了可控的合成过程,并验证了其在电化学CO2还原中的应用潜力.合成过程中,通过使用封装剂十八烷基三甲基氯化铵,成功地将Au@CuxO纳米球转化为层状CuAg纳米花(HNFs).有趣的是,该过程中原位形成了作为构建单元的纳米薄片.通过对CuAg HNFs与Na2PdCl4进行电偶置换,除去了Ag和Cu,引入了零价的Pd,并在纳米片上形成了大量孔隙.我们对这些CuAg电催化剂进行了CO2RR测试,结果显示Pd0.7Cu40.0Ag59.7 PHNs在C2+产物选择性(69.5%)和C2+分电流密度(-349.1 mA·cm-2)方面表现出最佳性能.密度泛函理论(DFT)模拟表明,PdAgCu表面具有独特的电子性质,降低了C-C偶联反应的能垒,凸显了Pd掺杂对CuAg电催化剂CO2还原的卓越性能.本研究为基于多孔纳米薄片构建多层次多金属纳米结构提供了一种直观方法,并验证了其在电催化方面的结构优势,为高效的CO2RR催化剂的合理设计提供了依据.
Abstract
In recent years,Cu-based multi-metallic nanocrystals with controlled elemental distributions have been extensively studied for potential applications as electrocatalysts for CO2 reduction reaction(CO2RR).Modifying Cu electrocatalysts with secondary or additional metals offers a viable approach to manipulate the overall d-band structure which would cause the shift in the d-band center.Such manipulation can affect the surface affinity of Cu towards key intermediates and thus the following catalytic pathway.Apart from endeavors to adjust the electronic structure,morphological engineering provides effective avenues to enhance the electrocatalytic performance of CO2RR.In contrast to quasi-spherical particles with irregular shapes,a 3D-assembled porous structure utilizing 2D nanosheets as building blocks offers advantages such as maximizing surface atom exposure and creating numerous diffusion channels and reactive sites for intermediates formed during catalysis.Yet,it is technique challenging to construct such type of nano-architecture via a rationally-design synthetic routes and traditional stepwise self-assembling strategy is time-consuming and lack of versatile control over the structural parameters of resulting products.Therefore,it holds significant value to develop a synthesis method capable of yielding high-purity formations of unique nanostructures.These structures should possess accurately controlled elemental compositions and electronic configurations,and establish a potential correlation between structural benefits and enhanced electrochemical performance in CO2RR.Herein,we report the controlled synthesis of palladium-copper-silver(Pd-Cu-Ag)nanocrystals with rationally-designed two-dimensional(2D)-three-dimensional(3D)hybrid architectures and validated with the promising use for electrochemical CO2 reduction(CO2RR).The synthetic procedure includes the conversion of Au@CuxO nanospheres into CuAg hierarchical nanoflowers(HNFs),as directed by the capping agent octadecyltrimethyl ammonium chloride.Interestingly,the nanosheets are formed in situ as the building block.Following galvanic replacement reaction between CuAg HNFs and Na2PdCl4 removes Ag and Cu,introduces zero-valent Pd,and creates abundant pores on the nanosheets.These CuAg-based products are tested as CO2RR electrocatalysts,in which the Pd0.7Cu40.0Ag59.7 PHNFs displayed the optimized performance in terms of C2+products selectivity(69.5%)and C2+partial current density(-349.1 mA·cm-2).As revealed by density functional theory(DFT)simulations,PdAgCu surface has distinct electronic property,which lower the reaction barrier for C-C coupling,protruding the exceptional advantage of the Pd doping towards CuAg electrocatalysts for CO2 reduction.The present study offers a straightforward approach to fabricate hierarchical multi-metallic nanostructures with the porous nanosheet as building block,and validates its structural advantage in electrocatalysis,shedding light on the rational design of efficient CO2RR catalyst.
基金项目
国家自然科学基金(21701100)
山东省自然科学基金(2020MB048)
山东省自然科学基金(ZR2022MB120)
山东省高等学校青创人才引育计划(储能与环境材料团队)()
山东省能源转化与纳米催化高校特色实验室()
济宁学院博士启动经费(2020BSZX01)
济宁学院"百名卓越人才"支持计划(2020ZYRC05)
苏州功能纳米与软物质重点实验室()
苏州市纳米科技协同创新中心111项目()
碳基功能材料与器件国际联合研究实验室()
万方数据