Full atomistic reaction mechanism with kinetics for CO reduction on Cu(100) from ab initio molecular dynamics free-energy calculations at 298 K
Full atomistic reaction mechanism with kinetics for CO reduction on Cu(100) from ab initio molecular dynamics free-energy calculations at 298 K
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DOI：
10.1073/pnas.1612106114
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发表时间：
2017-02-21
影响因子：
11.1
通讯作者：
Goddard, William A., III
中科院分区：
文献类型：
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作者：
Cheng, Tao;Xiao, Hai;Goddard, William A., III
NA实现选择性和有效地将CO2还原为特定烃和含氧化合物的新型催化剂的合理设计的关键步骤是确定详细的反应机制，包括动力学和产物选择性，作为已知系统的pH值和应用潜力的函数。为了实现这一点，我们应用从头算分子代谢动力学模拟（AIMD）的水/Cu（100）系统与五层显式溶剂下的电位为-0.59 V [可逆氢电极（RHE）]在pH 7和与实验进行比较。从这些自由能计算，我们确定了主要产品（乙烯和甲烷）和次要产品（乙醇，乙二醛，乙醇醛，乙二醇，乙醛，乙烷和甲醇）的动力学和途径。对于大于-0.6V（RHE）的施加电势（U），使用H2O + e（-）经由Eley-Rideal（ER）机理产生主要产物乙烯。速率决定步骤（RDS）是两个CO的C-C耦合，Δ G不渐近至= 0.69 eV。对于小于-0.60V（RHE）的施加电位，乙烯形成速率降低，主要是由于CO表面位点的损失，其被H* 取代。在U小于-0.85 V时，C2 H4沿着CH 4的再现是由于通过H* 与未吸附CO的ER过程产生的 *CHO形成（一个独特的结果）。该 *CHO是形成CH 4和C2 H4的常见中间体。这些结果表明，为了在pH 7下选择性和有效地获得烃产物，我们需要通过改变溶剂或合金化表面来增加CO浓度。
NA critical step toward the rational design of new catalysts that achieve selective and efficient reduction of CO2 to specific hydrocarbons and oxygenates is to determine the detailed reaction mechanism including kinetics and product selectivity as a function of pH and applied potential for known systems. To accomplish this, we apply ab initio molecular metadynamics simulations (AIMD) for the water/Cu(100) system with five layers of the explicit solvent under a potential of -0.59 V [ reversible hydrogen electrode (RHE)] at pH 7 and compare with experiment. From these free-energy calculations, we determined the kinetics and pathways for major products (ethylene and methane) and minor products (ethanol, glyoxal, glycolaldehyde, ethylene glycol, acetaldehyde, ethane, and methanol). For an applied potential (U) greater than -0.6 V (RHE) ethylene, the major product, is produced via the Eley-Rideal (ER) mechanism using H2O + e(-). The rate-determining step (RDS) is C-C coupling of two CO, with Delta G not asymptotic to = 0.69 eV. For an applied potential less than -0.60 V (RHE), the rate of ethylene formation decreases, mainly due to the loss of CO surface sites, which are replaced by H*. The reappearance of C2H4 along with CH4 at U less than -0.85 V arises from *CHO formation produced via an ER process of H* with nonadsorbed CO (a unique result). This *CHO is the common intermediate for the formation of both CH4 and C2H4. These results suggest that, to obtain hydrocarbon products selectively and efficiency at pH 7, we need to increase the CO concentration by changing the solvent or alloying the surface.