Interstitial carbon atoms enhance both selectivity and activity of rhodium catalysts toward C-C cleavage in direct ethanol fuel cells
Interstitial carbon atoms enhance both selectivity and activity of rhodium catalysts toward C-C cleavage in direct ethanol fuel cells
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DOI：
10.1016/j.nanoen.2023.108597
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发表时间：
2023-08
期刊：
影响因子：
17.6
通讯作者：
Zhenming Cao;Huiqi Li;Qiyuan Fan;Zhantao Liu;Zitao Chen;Yunchao Sun;Jinyu Ye;Maofeng Cao
中科院分区：
文献类型：
--
作者：
Zhenming Cao;Huiqi Li;Qiyuan Fan;Zhantao Liu;Zitao Chen;Yunchao Sun;Jinyu Ye;Maofeng Cao
乙醇中C-C键的选择性断裂是许多工业过程的关键，包括直接乙醇燃料电池和蒸汽重整的操作。间隙碳原子在贵金属催化剂的表面下区域的选择性和活性有重大影响，但由于其原位形成和亚稳性的性质，对机理细节的理解仍然是难以捉摸的。在此，我们开发了一种方法，以获得稳定的RhCx（x ≤ 0.5）通过引入C原子到间隙的位置，良好定义的Rh纳米片的8-10原子。层的厚度，并进一步阐明了间隙C原子的电子和几何效应的C-C键断裂。随着C原子引入到八面体位置的一半中，Rh晶格从立方结构变为正交结构。C原子的插入引起的晶格膨胀以及C原子和Rh原子之间的电子转移有效地抑制了OH ~* 和CH_3CO ~* 之间的偶联反应，同时使C-C键的断裂放热更大。因此，我们获得了高达18.1%的乙醇到CO2的选择性，远高于Rh对应物（10.0%），以及3.1倍的动力学改进。在这些发现的指导下，还开发了一种新的方法，将C原子直接引入到商业Rh黑的表面下，以分别提高其选择性和活性2.5倍和1.6倍。
Selective breaking of the C-C bond in ethanol holds the key to many industrial processes, including the operation of direct ethanol fuel cells and steam reforming. Interstitial C atoms in the subsurface region of noble-metal catalysts have major impacts on the selectivity and activity, but an understanding of the mechanistic details is still elusive due to their nature of in situ formation and metastability. Herein, we develop a method to obtain stable RhCx(x ≈ 0.5) by introducing C atoms into the interstitial sites of well-defined Rh nanosheets of 8–10 at. layers in thickness, and further elucidate the electronic and geometric effects of the interstitial C atoms on the cleavage of C-C bond. With the introduction of C atoms into half of the octahedral sites, the Rh lattice changes from a cubic to an orthorhombic structure. The lattice expansion induced by the insertion of C atoms, together with the electron transfer between C and Rh atoms, effectively suppresses the coupling reaction between OH* and CH3CO* to form acetic acid while making the cleavage of C-C bond more exothermic. As such, we obtain a selectivity of ethanol to CO2as high as 18.1 %, much higher than those of the Rh counterpart (10.0 %), together with 3.1-fold improvement in kinetics. Guided by these findings, a new method is also developed to directly introduce C atoms into the subsurface of a commercial Rh black to enhance its selectivity and activity by 2.5- and 1.6- folds, respectively.