Department of Chemistry, Tufts University, Medford, Massachusetts 02155-5813, USA.
Nat Mater. 2013 Jun;12(6):523-8. doi: 10.1038/nmat3620. Epub 2013 Apr 21.
Spillover of reactants from one active site to another is important in heterogeneous catalysis and has recently been shown to enhance hydrogen storage in a variety of materials. The spillover of hydrogen is notoriously hard to detect or control. We report herein that the hydrogen spillover pathway on a Pd/Cu alloy can be controlled by reversible adsorption of a spectator molecule. Pd atoms in the Cu surface serve as hydrogen dissociation sites from which H atoms can spillover onto surrounding Cu regions. Selective adsorption of CO at these atomic Pd sites is shown to either prevent the uptake of hydrogen on, or inhibit its desorption from, the surface. In this way, the hydrogen coverage on the whole surface can be controlled by molecular adsorption at a minority site, which we term a 'molecular cork' effect. We show that the molecular cork effect is present during a surface catalysed hydrogenation reaction and illustrate how it can be used as a method for controlling uptake and release of hydrogen in a model storage system.
反应物从一个活性位向另一个活性位的溢出在多相催化中很重要，最近已被证明可以提高各种材料的储氢能力。氢的溢出很难检测或控制。我们在此报告称，通过可逆吸附 spectator 分子，可以控制 Pd/Cu 合金上的氢溢出途径。Cu 表面上的 Pd 原子作为氢离解位点，H 原子可以从这些位点溢出到周围的 Cu 区域。选择性吸附 CO 到这些原子 Pd 位点上，要么阻止氢在表面上的吸收，要么抑制其从表面上的脱附。通过这种方式，可以通过在少数位点上的分子吸附来控制整个表面上的氢覆盖率，我们称之为“分子塞子”效应。我们表明，在表面催化的加氢反应过程中存在分子塞子效应，并说明了如何将其用作控制模型存储系统中氢的吸收和释放的方法。
