Cu-Pt-Au三元合金催化水煤气变换反应的密度泛函研究

Density functional study of water gas shift reaction catalyzed by Cu-Pt-Au ternary alloy

利用密度泛函理论(DFT)研究了不同掺杂量的Cu-Pt-Au催化剂性质及水煤气变换反应(WGSR)在催化剂表面上的反应机理。首先对Cu-Au和Pt-Au二元催化剂的稳定性和电子活性进行研究,发现Pt-Au催化剂的协同效应较优,稳定性更优,结合能为77.15eV,d带中心为-3.18eV。当将Cu继续掺杂到Pt-Au合金中构成Cu-Pt-Au三元催化剂时,Cu3-Pt3-Au(111)结合能为77.99eV,且d带中心为-3.05eV,表明其具有较优的稳定性和电子活性。探讨了WGSR在Cu3-Pt3-Au(111)上的反应历程,氧化还原机理因CO氧化的能垒达到4.84eV而不易进行。CHO和COOH两个中间体为竞争关系,且形成CHO中间物时的能垒较小,因此,反应相对容易按照甲酸机理进行。

The reaction path and the reaction mechanism of water gas shift reaction (WGSR) on the Cu-Pt-Au catalyst surface were investigated using density functional theory (DFT). The stability and electron activity of binary and ternary catalysts composed of Cu, Pt and Au were studied. The synergistic effect of Pt-Au catalyst in binary alloy is better, and the binding energy of Pt 3-Au(111) surface is 77.15 eV, and energy level of d -band center is -3.18 eV. When the Pt 3-Au(111) surface continues to be doped with Cu, the binding energy of Cu 3-Pt 3-Au(111) is 77. 99 eV and the center of d -band is -3. 05 eV according to the binding energy and density of stares. The energy barrier of CO oxidization is 4.84 eV in the redox mechanism. The reaction is not easy to follow the redox mechanism. Moreover, the two intermediates CHO and COOH are competitive, the energy barrier of forming COOH is larger than that of forming CHO, the reaction is more easily carried out according to the formic acid mechanism.