Chu Yun-Jie, Zhu Chang-Yan, Liu Chun-Guang, Geng Yun, Su Zhong-Min, Zhang Min
Institute of Functional Material Chemistry, Faculty of Chemistry, National & Local United Engineering Laboratory for Power Batteries, Northeast Normal University Changchun 130024 China
Department of Chemistry, Faculty of Science, Beihua University Jilin City 132013 P. R. China
Chem Sci. 2024 Aug 2;15(34):13976-86. doi: 10.1039/d4sc03944k.
Acetaldehyde (AA) and ethylene oxide (EO) are important fine chemicals, and are also substrates with wide applications for high-value chemical products. Direct electrocatalytic oxidation of ethylene to AA and EO can avoid the untoward effects from harmful byproducts and high energy emissions. The most central intermediate state is the co-adsorption and coupling of ethylene and active oxygen intermediates (*O) at the active site(s), which is restricted by two factors: the stability of the *O intermediate generated during the electrolysis of water on the active site at a certain applied potential and pH range; and the lower kinetic energy barriers of the oxidation process based on the thermo-migration barrier from the *O intermediate to produce AA/EO. The benefit of two adjacent active atoms is more promising, since diverse adsorption and flexible catalytic sites may be provided for elementary reaction steps. Motivated by this strategy, we explored the feasibility of various homonuclear TMN@graphenes with dual-atomic-site catalysts (DASCs) for ethylene electro-oxidation through first-principles calculations thermodynamic evaluation, analysis of the surface Pourbaix diagram, and kinetic evaluation. Two reaction mechanisms through C-TM TM-TM synergism were determined. Between them, a TM-TM mechanism on 4 TMN@graphenes and a C-TM mechanism on 5 TMN@graphenes are built. All 5 TMN@graphenes through the C-TM mechanism exhibit lower kinetic energy barriers for AA and EO generation than the 4 TMN@graphenes through the TM-TM mechanism. In particular, PdN@graphene exhibits the most excellent catalytic activity, with energy barriers for generating AA and EO of only 0.02 and 0.65 eV at an applied potential of 1.77 V RHE for the generation of an active oxygen intermediate. Electronic structure analysis indicates that the intrinsic C-TM mechanism is more advantageous than the TM-TM mechanism for ethylene electro-oxidation, and this study also provides valuable clues for further experimental exploration.
乙醛（AA）和环氧乙烷（EO）是重要的精细化学品，也是用于高价值化学产品的具有广泛应用的底物。乙烯直接电催化氧化为AA和EO可以避免有害副产物和高能量排放带来的不良影响。最核心的中间状态是乙烯与活性氧中间体（O）在活性位点的共吸附和偶联，这受到两个因素的限制：在一定的外加电势和pH范围内，水在活性位点电解过程中生成的O中间体的稳定性；以及基于从*O中间体产生AA/EO的热迁移势垒，氧化过程的较低动能势垒。两个相邻活性原子的益处更具前景，因为可以为基元反应步骤提供多样的吸附和灵活的催化位点。受此策略的启发，我们通过第一性原理计算、热力学评估、表面Pourbaix图分析和动力学评估，探索了各种具有双原子位点催化剂（DASC）的同核TMN@石墨烯用于乙烯电氧化的可行性。确定了通过C-TM和TM-TM协同作用的两种反应机制。其中，构建了4种TMN@石墨烯上的TM-TM机制和5种TMN@石墨烯上的C-TM机制。所有通过C-TM机制的5种TMN@石墨烯在生成AA和EO方面均表现出比通过TM-TM机制的4种TMN@石墨烯更低的动能势垒。特别是，PdN@石墨烯表现出最优异的催化活性，在施加1.77 V（相对于可逆氢电极，RHE）电势以生成活性氧中间体时，生成AA和EO的能垒仅为0.02和0.65 eV。电子结构分析表明，对于乙烯电氧化，内在的C-TM机制比TM-TM机制更具优势，本研究也为进一步的实验探索提供了有价值的线索。
