Operando Insight into the Correlation between the Structure and Composition of CuZn Nanoparticles and Their Selectivity for the Electrochemical CO2 Reduction
Operando Insight into the Correlation between the Structure and Composition of CuZn Nanoparticles and Their Selectivity for the Electrochemical CO2 Reduction
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DOI：
10.1021/jacs.9b10709
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发表时间：
2019-12-18
影响因子：
15
通讯作者：
Roldan Cuenya, Beatriz
中科院分区：
文献类型：
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作者：
Jeon, Hyo Sang;Timoshenko, Janis;Roldan Cuenya, Beatriz
为了实现二氧化碳电化学还原(CO2RR)过程中的选择性控制，双金属CuZn催化剂最近被提出作为替代催化剂。然而，对决定CO2RR性能的潜在反应机理和参数的基本了解仍然缺乏。在本研究中，我们使用了尺寸可控的(类似于5 nm)Cu100-xZnx纳米粒子(NPs)在碳载体上，研究了它们的结构和组成与催化性能之间的关系。通过调节锌的浓度，大大提高了甲烷的选择性[类似于70%的法拉第效率(F.E.)]当锌含量在10~50之间时，H-2的产生受到抑制。含锌浓度较高的样品，甲烷生成量显著降低，CO选择性发生突变。用准原位X射线光电子能谱(XPS)分析了金属的浸出情况。操纵面X射线吸收精细结构(XAFS)测量表明，铜原子与锌原子的合金化是在反应条件下进行的，并对产物的选择性起着决定性作用。随时间变化的XAFS分析表明，在CO2RR过程中，铜原子周围的局域结构和化学环境持续演化了几个小时。特别是，最初存在的阳离子锌物种随着反应的进行而被还原，导致形成铜锌合金(黄铜)。研究发现，在CO2RR过程中，铜锌相互作用随时间的变化是导致铜锌纳米颗粒对甲烷的选择性转变为铜锌合金纳米颗粒对CO选择性的原因。这项研究强调了深入了解双金属NP电催化剂中不同原子物种在Operando反应条件下相互作用的重要性，以了解并最终调整其反应活性。
Bimetallic CuZn catalysts have been recently proposed as alternatives in order to achieve selectivity control during the electrochemical reduction of CO2 (CO2RR). However, fundamental understanding of the underlying reaction mechanism and parameters determining the CO2RR performance is still missing. In this study, we have employed size-controlled (similar to 5 nm) Cu100-xZnx nanoparticles (NPs) supported on carbon to investigate the correlation between their structure and composition and catalytic performance. By tuning the concentration of Zn, a drastic increase in CH4 selectivity [similar to 70% Faradaic efficiency (F.E.)] could be achieved for Zn contents from 10 to 50, which was accompanied by a suppression of the H-2 production. Samples containing a higher Zn concentration displayed significantly lower CH4 production and an abrupt switch in the selectivity to CO. Lack of metal leaching was observed based on quasi in situ X-ray photoelectron spectroscopy (XPS). Operando X-ray absorption fine structure (XAFS) spectroscopy measurements revealed that the alloying of Cu atoms with Zn atoms takes place under reaction conditions and plays a determining role in the product selectivity. Time -dependent XAFS analysis showed that the local structure and chemical environment around the Cu atoms continuously evolve during CO2RR for several hours. In particular, cationic Zn species initially present were found to get reduced as the reaction proceeded, leading to the formation of a CuZn alloy (brass). The evolution of the Cu-Zn interaction with time during CO2RR was found to be responsible for the change in the selectivity from CH4 over Cu-ZnO NPs to CO over CuZn alloy NPs. This study highlights the importance of having access to in depth information on the interplay between the different atomic species in bimetallic NP electrocatalysts under operando reaction conditions in order to understand and ultimately tune their reactivity.