Modulating Electrocatalysis on Graphene Heterostructures: Physically Impermeable Yet Electronically Transparent Electrodes
Modulating Electrocatalysis on Graphene Heterostructures: Physically Impermeable Yet Electronically Transparent Electrodes
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DOI：
10.1021/acsnano.8b00702
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发表时间：
2018-03-01
期刊：
影响因子：
17.1
通讯作者：
Rodriguez-Lopez, Joaquin
中科院分区：
文献类型：
--
作者：
Hui, Jingshu;Pakhira, Srimanta;Rodriguez-Lopez, Joaquin
石墨烯的电子特性和极薄的厚度使其成为探索不同环境中电化学相互作用的有吸引力的平台。在这里，我们报告的系统调谐的电催化活性对氧还原反应（ORR）通过由石墨烯改性与金属底层和吸附层组成的分子催化剂形成的异质结构。图案化电极的系统伏安测试和电化学成像使我们能够自信地探测ORR机制和过电位的修改。我们发现，表面构型在很大程度上决定了ORR机制，卟啉分子催化剂的吸附层显示出比石墨烯裸露基面更高的2 e（-）途径活性。然而，令人惊讶的是，底层材料以Pt > Au > SiOx的顺序实质上有助于降低ORR的活化电位，这强烈表明溶液排斥金属参与反应。计算研究表明，ORR增强源于金属d-亚壳层电子通过石墨烯层的渗透。此外，这些物理不可渗透但电子透明的电极显示出对氰化物中毒的耐受性和长期循环的稳定性，突出了石墨烯作为贵金属的有效保护层，同时实现电化学相互作用。这项工作具有影响的2D材料和核-壳型异质结构的电催化反应的机理的理解。
The electronic properties and extreme thinness of graphene make it an attractive platform for exploring electrochemical interactions across dissimilar environments. Here, we report on the systematic tuning of the electrocatalytic activity toward the oxygen reduction reaction (ORR) via heterostructures formed by graphene modified with a metal underlayer and an adlayer consisting of a molecular catalyst. Systematic voltammetric testing and electrochemical imaging of patterned electrodes allowed us to confidently probe modifications on the ORR mechanisms and overpotential. We found that the surface configuration largely determined the ORR mechanism, with adlayers of porphyrin molecular catalysts displaying a higher activity for the 2e(-) pathway than the bare basal plane of graphene. Surprisingly, however, the underlayer material contributed substantially to lower the activation potential for the ORR in the order Pt > Au > SiOx, strongly suggesting the involvement of the solution-excluded metal on the reaction. Computational investigations suggest that ORR enhancements originate from permeation of metal d-subshell electrons through the graphene layer. In addition, these physically impermeable but electronically transparent electrodes displayed tolerance to cyanide poisoning and stability toward long-term cycling, highlighting graphene as an effective protection layer of noble metal while enabling electrochemical interactions. This work has implications in the mechanistic understanding of 2D materials and core-shell-type heterostructures for electrocatalytic reactions.