Microwave-Enabled Incorporation of Single Atomic Cu Catalytic Sites in Holey Graphene: Unifying Structural Requirements of a Carbon Matrix for Simultaneous Achievement of High Activity and Long-Term Durability
Microwave-Enabled Incorporation of Single Atomic Cu Catalytic Sites in Holey Graphene: Unifying Structural Requirements of a Carbon Matrix for Simultaneous Achievement of High Activity and Long-Term Durability
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DOI：
10.1021/acsaem.0c00704
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发表时间：
2020-08
影响因子：
6.4
通讯作者：
Qingdong Li;Hongbin Yang;J. Ouyang;M. Solovyev;Nicole Lahanas;C. Flach;R. Mendelsohn;E. Garfunkel-E.-Ga
中科院分区：
文献类型：
--
作者：
Qingdong Li;Hongbin Yang;J. Ouyang;M. Solovyev;Nicole Lahanas;C. Flach;R. Mendelsohn;E. Garfunkel-E.-Ga
这项工作报告了我们在微波热解金属有机框架的首次探索中的发现。提出了一种省时、节能的电化学单原子催化剂直接制备方法，无需后处理。制备的E-SAC最独特的结构是，铜催化位点不像传统热解那样位于无定形碳基体中，而是位于原始多孔石墨烯纳米片的基面上。制备的Cu-E-SAC在酸性和碱性介质中均表现出优异的氧还原水催化活性和选择性。与迄今为止报道的所有Cu-E-SACs和大多数基于过渡金属的E-SACs不同，期望的直接4e -途径在酸性介质中比在碱性介质中更有利。优异的性能归功于催化位点的独特结构。多孔石墨烯材料中的大石墨烯畴提供了更高的离域富电子π带，提高了Cu中心的d轨道能级。因此，它们对分子氧的结合强度大大增强，改善了氧还原反应，并可能促进直接的4e -途径，同时最大限度地减少了过氧化氢副产物的产生。考虑到多孔石墨烯材料的高导电性和优异的抗氧化稳定性，这项工作首次提出了碳基质对高催化活性和长期耐用性的矛盾结构要求可以统一并同时得到满足。结合制造多孔石墨烯和E-SACs的简单和快速的优点，这项工作为解决无贵金属单原子催化剂的关键挑战提供了一种可能的策略。
This work reports our discoveries from the first exploration in microwave pyrolysis of a metal–organic framework. A time- and energy-efficient approach was developed for direct fabrication of electrochemical single-atom catalysts (E-SACs) without the requirement of post-treatment. The most unique structure of the fabricated E-SAC is that the Cu catalytic sites were not in the amorphous carbon matrix as those achieved via traditional pyrolysis but in the basal planes of pristine holey graphene nanoplatelets. The as-prepared Cu-E-SAC exhibits excellent catalytic activity and selectivity in reducing oxygen to water in both acidic and alkaline media. The desired direct 4e– pathway is more favorable in acidic versus alkaline media, which is different from all the Cu-E-SACs reported so far and most transition-metal-based E-SACs. The superior performance is attributed to the unique structure of the catalytic sites. The large graphene domains in the holey graphene materials provide higher delocalized electron-rich π band and increase the d-orbital energy level of the Cu centers. Consequently, their binding strength for molecular oxygen is largely enhanced, improving the oxygen reduction reaction and likely promoting a direct 4e– pathway with minimized generation of a peroxide byproduct. Considering the high conductivity and excellent stability against oxidation of the holey graphene material, this work, for the first time, suggests that the contradictory structural requirement of a carbon matrix for high catalytic activity and long-term durability can be unified and simultaneously satisfied. Combined with the merits of simplicity and rapidness for fabricating both holey graphene and E-SACs, this work provides a possible strategy to address the critical challenges of precious metal-free single-atom catalysts.