Okafor Andrew, Shelton William A, Xu Ye
Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, Louisiana 70803, United States.
Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, United States.
J Phys Chem C Nanomater Interfaces. 2024 Jun 29;128(27):11145-11158. doi: 10.1021/acs.jpcc.4c01308. eCollection 2024 Jul 11.
The bulk properties and surface chemical reactivity of compositionally disordered Pt-Fe and Pt-Co alloys in the A1 phase have been investigated theoretically in comparison to the ordered alloys of the same compositions. The results are analyzed together with our previously reported findings for Pt-Ni. Nonlinear variation is observed in lattice constant, d band center, magnetic moment, and hydrogen adsorption energy across the composition range (0-100 atomic % of Pt, ). The Pt 5d states are strongly perturbed by the 3d states of the base metals, leading to notable density of states above the Fermi level and residual magnetic moments at high . Surface reactivity in terms of average H adsorption energy varies continuously with composition between the monometallic Fe-Pt and Co-Pt limits, going through a maximum around = 0.5-0.75. Close inspection reveals a significant variation in site reactivity at < 0.75, particularly with disordered Pt-Fe alloys due in part to the inherent disparity in chemical reactivity between Fe and Pt. Furthermore, the strong interaction between Fe and Pt causes Pt-rich sites to be less reactive toward H than Pt-rich sites on disordered Pt-Ni alloy surfaces, despite less compressive strain caused. These results provide theoretical underpinnings for conceptualizing and understanding the performance of these Pt-base metal alloys in key catalytic applications and for efforts to tailor Pt-alloys as catalysts.
理论上研究了A1相成分无序的Pt-Fe和Pt-Co合金的整体性质和表面化学反应活性，并与相同成分的有序合金进行了比较。研究结果与我们之前报道的Pt-Ni的研究结果一起进行了分析。在整个成分范围（Pt的原子百分比为0-100%）内，观察到晶格常数、d带中心、磁矩和氢吸附能的非线性变化。Pt的5d态受到贱金属3d态的强烈扰动，导致费米能级以上的态密度显著增加，并且在高成分时出现剩余磁矩。就平均H吸附能而言，表面反应活性在单金属Fe-Pt和Co-Pt极限之间随成分连续变化，在约0.5-0.75处出现最大值。仔细观察发现，在成分小于0.75时，位点反应活性有显著变化，特别是对于无序的Pt-Fe合金，部分原因是Fe和Pt之间化学反应活性的固有差异。此外，Fe和Pt之间的强相互作用导致无序Pt-Ni合金表面上富Pt位点对H的反应性低于富Pt位点，尽管产生的压缩应变较小。这些结果为理解和概念化这些Pt基金属合金在关键催化应用中的性能以及为定制Pt合金作为催化剂的努力提供了理论基础。
