Unraveling Electroreductive Mechanisms of Biomass-Derived Aldehydes via Tailoring Interfacial Environments
Unraveling Electroreductive Mechanisms of Biomass-Derived Aldehydes via Tailoring Interfacial Environments
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DOI：
10.1021/acscatal.2c03163
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发表时间：
2022-11
期刊：
影响因子：
12.9
通讯作者：
Hengzhou Liu;Deep Patel;Yifu Chen;Jungkuk Lee;Ting-Han Lee;S. Cady;Eric W. Cochran;Luke T. Roling;Wenzheng Li
中科院分区：
文献类型：
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作者：
Hengzhou Liu;Deep Patel;Yifu Chen;Jungkuk Lee;Ting-Han Lee;S. Cady;Eric W. Cochran;Luke T. Roling;Wenzheng Li
生物质衍生原料的电化学还原在生产由可再生电力驱动的增值化学品或燃料方面具有很大的前景。然而，在分子水平上的界面区域内的醛还原朝向有价值的产品的机制的理解仍然缺乏。本文通过对局部环境（包括H/D组成、局部H3 O+和H2O含量）的调整，研究了酸性条件下糠醛在铅电极上的还原反应，并阐明了3种关键产物：糠醇（FA）、2-甲基呋喃（MF）和氢糠偶姻（hydrofuroin）的生成途径。通过结合同位素标记和掺入研究，我们发现，质子源（H2O和H3 O+）在FA和MF的氢化和氢解途径中分别起着至关重要的作用。特别是，H/D和表面性质依赖的氢化/氘代途径的产物选择性动力学同位素效应强烈影响FA的产生，但不影响MF，这是由于它们的不同速率决定步骤。电动力学研究进一步表明，Langmuir-Hinshelwood和Eley-Rideal途径分别形成FA和MF。通过用大半径阳离子修饰双电层，我们进一步将产物选择性（FA和MF）与界面环境（局部H3 O+和H2O含量、界面电场和微分电容）相关联。最后，实验和计算研究表明，对hydrofuroin和FA的竞争途径：hydrofuroin是有利地产生在电解质中通过自偶联的酮基自由基，这是形成从外层，单电子转移，而FA是从氢化产生的吸附糠醛/酮基自由基在电极表面上。
Electrochemical reduction of biomass-derived feedstocks holds great promise to produce value-added chemicals or fuels driven by renewable electricity. However, mechanistic understanding of the aldehyde reduction toward valuable products at the molecular level within the interfacial regions is still lacking. Herein, through tailoring the local environments, including H/D composition and local H3O+and H2O content, we studied the furfural reduction on Pb electrodes under acid conditions and elucidated the pathways toward three key products: furfuryl alcohol (FA), 2-methylfuran (MF), and hydrofuroin. By combining isotopic labeling and incorporation studies, we revealed that the source of protons (H2O and H3O+) plays a critical role in the hydrogenation and hydrogenolysis pathways toward FA and MF, respectively. In particular, the product-selective kinetic isotopic effect of H/D and the surface-property-dependent hydrogenation/deuteration pathway strongly impacted the generation of FA but not MF, owing to their different rate-determining steps. Electrokinetic studies further suggested Langmuir–Hinshelwood and Eley–Rideal pathways in the formation of FA and MF, respectively. Through modifying the double layer by cations with large radii, we further correlated the product selectivity (FA and MF) with interfacial environments (local H3O+and H2O contents, interfacial electric field, and differential capacitances). Finally, experimental and computational investigations suggested competitive pathways toward hydrofuroin and FA: hydrofuroin is favorably produced in the electrolyte through the self-coupling of ketyl radicals, which are formed from outer-sphere, single-electron transfer, while FA is generated from hydrogenation of the adsorbed furfural/ketyl radical on the electrode surface.