氧化气氛中PdAg纳米合金的表面相稳定性与原子电荷的关系  

Surface Phase Stability of PdAg Nanoalloys and Its Relevance to Atomic Charge in Oxidizing Atmospheres

作　　者：卞维琦 梁雪松 Bian Weiqi;Liang Xuesong(China State Shipbuilding Corporation Limited 723 Research Institute,Yangzhou 225009,Jiangsu,China)

机构地区：[1]中国船舶集团有限公司第七二三研究所,江苏扬州225009

出　　处：《科技通报》2024年第5期1-7,共7页Bulletin of Science and Technology

基　　金：某舰雷达侦查设备专项研制(21Y61A)。

摘　　要：在多相催化中,纳米合金的氧化和偏析可能导致特殊的电催化性质。基于第一性原理原子热力学方法,本文通过表面相稳定性图计算氧化气氛中Pd_(6)@Ag_(32)和Ag_(6)@Pd_(32)核壳纳米合金的早期氧化阶段。Ag_(38)纳米团簇(Δμ_(0)=-0.95 eV)的稳定性高于Pd_(38)纳米团簇(Δμ_(0)=-1.3 eV),但是Pd_(6)@Ag_(32)核壳纳米合金(Δμ_(0)=-0.9 eV)显示出高于Ag_(38)纳米团簇的表面相稳定性,而Pd偏析的Pd_(6)@Ag_(32)纳米合金的稳定性低于Ag_(38)纳米团簇。同时,Ag_(6)@Pd_(32)核壳纳米合金(Δμ_(0)=-1.5 eV)的表面相稳定性比Pd_(38)纳米团簇低,而Ag偏析的Ag_(6)@Pd_(32)纳米合金显示出高于Pd_(38)纳米团簇的表面相稳定性。表面Ag原子偏析越多的Pd_(6)@Ag_(32)和Ag_(6)@Pd_(32)核壳纳米合金具有更高的表面相稳定性。表面相稳定性的顺序遵循原子电荷的趋势,即越多的负电荷对应于越低的表面相稳定性。研究结果能够为设计燃料电池中具有合适表面相稳定性的PdAg基纳米合金催化剂提供有效信息。The oxidation and segregation of nanoalloys can lead to unique electrocatalytic performance in heterogeneous catalysis.The early stage of oxidation on Pd_(6)@Ag_(32)and Ag_(6)@Pd_(32)core-shell nanoalloys was calculated by the surface phase stability diagrams using a first-principles atomistic thermodynamics method in oxidizing atmospheres.Ag_(38)nanoparticle withΔμ_(0)=-0.95 eV is more stable than Pd_(38)nanoparticle withΔμ_(0)=-1.3 eV.Unexpectedly,Pd_(6)@Ag_(32)core-shell nanoalloy withΔμ_(0)=-0.9 eV exhibits better surface phase stability than Ag_(38)nanoparticle but Pd-segregated Pd_(6)@Ag_(32)nanoalloys have lower stability than Ag_(38)nanoparticle,and Ag_(6)@Pd_(32)core-shell nanoalloy withΔμ_(0)=-1.5 eV displays lower surface phase stability than Pd_(38)nanoparticle but Ag-segregated Ag_(6)@Pd_(32)nanoalloys show better surface phase stability than Pd_(38)nanoparticle.Surface-segregated Pd_(6)@Ag_(32)and Ag_(6)@Pd_(32)core-shell nanoalloys with more surface Ag atoms tend to possess the higher surface phase stability.The order of surface phase stability follows the same trend of atomic charges,that is,the more negative charges corresponding to the lower surface phase stability.The results can provide useful information for designing PdAg-based catalyst materials with appropriate surface phase stability towards fuel cells.

关 键 词：纳米合金 密度泛函理论 表面偏析 表面相稳定性 原子电荷 

分 类 号：O642[理学—物理化学]