How zinc helps copper make methanol
Copper nanoparticles can catalyze the formation of methanol from a mixture of CO2, CO, and H2, but adding zinc oxide nanoparticles, themselves inactive in this reaction, greatly boosts the rates. Kuld et al. measured how methanol synthesis activity varies with the coverage of zinc atoms on the copper nanoparticles, as determined experimentally and with density functional theory calculations. The ZnO nanoparticle size determined how much zinc covers the copper surface and in turn controlled the catalyst activity.
Abstract
Promoter elements enhance the activity and selectivity of heterogeneous catalysts. Here, we show how methanol synthesis from synthesis gas over copper (Cu) nanoparticles is boosted by zinc oxide (ZnO) nanoparticles. By combining surface area titration, electron microscopy, activity measurement, density functional theory calculations, and modeling, we show that the promotion is related to Zn atoms migrating in the Cu surface. The Zn coverage is quantitatively described as a function of the methanol synthesis conditions and of the size-dependent thermodynamic activities of the Cu and ZnO nanoparticles. Moreover, experimental data reveal a strong interdependency of the methanol synthesis activity and the Zn coverage. These results demonstrate the size-dependent activities of nanoparticles as a general means to design synergetic functionality in binary nanoparticle systems.
Science 20 May 2016:
Vol. 352, Issue 6288, pp. 969-974
DOI: 10.1126/science.aaf0718
http://science.sciencemag.org/content/352/6288/969
中文报道链接：最近，丹麦科学家利用表面滴定、电子显微镜、活性测量和密度泛函理论计算等研究了ZnO纳米颗粒对Cu纳米颗粒在催化合成气（H2, CO, and CO2的混合物）制备甲醇过程中的促进作用。研究表明，ZnO纳米颗粒的促进作用与Zn原子在Cu表面的迁移有关。研究人员构建了Zn原子的覆盖量（θZn）与甲醇合成条件的函数关系，发现了Cu和ZnO纳米颗粒热力学活性的尺寸依赖性。实验数据揭示了甲醇合成和Zn覆盖率具有很强的相关性。纳米颗粒尺寸依赖性对于设计协同功能的二元纳米颗粒系统具有重要的借鉴意义。（新材料在线）
