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[交流] CO2电化学还原反应中催化机制的理论计算研究

Highly effective sites and selectivity of nitrogen-doped graphene/CNT catalysts for CO2 electrochemical reduction
Guo-Liang Chai^1 and Zheng-Xiao Guo
1. g.chai@fjirsm.ac.cn
http://pubs.rsc.org/en/content/articlehtml/2015/sc/c5sc03695j
Metal-free catalysts, such as graphene/carbon nanostructures, are highly cost-effective to replace expensive noble metals for CO2 reduction if fundamental issues, such as active sites and selectivity, are clearly understood. Using both density functional theory (DFT) and ab initio molecular dynamic calculations, we show that the interplay of N-doping and curvature can effectively tune the activity and selectivity of graphene/carbon-nanotube (CNT) catalysts. The CO2 activation barrier can be optimized to 0.58 eV for graphitic-N doped graphene edges, compared with 1.3 eV in the un-doped counterpart. The graphene catalyst without curvature shows strong selectivity for CO/HCOOH production, whereas the (6, 0) CNT with a high degree of curvature is effective for both CH3OH and HCHO production. Curvature is also very influential to tune the overpotential for a given product, e.g. from 1.5 to 0.02 V for CO production and from 1.29 to 0.49 V for CH3OH production. Hence, the graphene/CNT nanostructures offer great scope and flexibility for effective tunning of catalyst efficiency and selectivity, as shown here for CO2 reduction.

CO2电化学还原反应的催化机制理论研究文章，大部分只根据反应中各个反应中间物的吸附能自由能变化来讨论可能的反应机制，而忽略了CO2的吸附势垒，也就是CO2电化学反应的第一步。这篇文章通过Car–Parrinello molecular dynamics并直接考虑水溶液的影响，模拟计算了CO2的吸附势垒，根据吸附势垒的大小筛选出最可能的吸附位。再进一步讨论各种反应步骤中可能产生的反应中间物的自由能从热力学上来确定最可能的反应步骤，以及最优的催化活性点。另外也提出了方法如何进一步优化催化活性点的活性。并从电子结构上揭示了费米能级附近电子态与催化活性的关系。

这篇文章对做CO2电化学还原催化理论研究的同学提供了一个很好的参考例子。

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