Adsorbed hydrogen (H) species on catalyst surfaces are important active intermediates in many catalytic reactions and detailed analyses of them are necessary to understand the catalyses. Inelastic neutron scattering (INS) enables direct and selective observation of H species due to the extremely large incoherent neutron scattering cross section of a hydrogen atom. In the present study, the adsorbed H species on some heterogeneous precious metal catalysts supported by alumina and carbon black were investigated by in situ INS spectroscopy with a newly designed sample cell. The newly designed double-walled long cell gave clear INS spectra with less elastic scattering. Three alumina-supported metal catalysts having Pt, Pd, and Rh metal nanoparticles with different particle sizes exhibited different INS spectra in intensities and band distribution. Observation of the H species on the metal nanoparticles and the alumina surface revealed their properties. In addition, the H atoms stored in Pd nanoparticles were observed as palladium hydride. In contrast, the H species on a Pt catalyst supported by carbon black were found to be strongly adsorbed on the carbon support. The properties of these H species were dependent on both the properties of the precious metals and those of the support materials.

在许多催化反应中，催化剂表面吸附的氢（H）物种是重要的活性中间体，对它们的详细分析对于理解催化剂是必需的。由于氢原子的超大非相干中子散射截面，非弹性中子散射（INS）可以直接和选择性地观察H物种。在本研究中，采用新设计的样品池，通过原位INS光谱研究了氧化铝和炭黑负载的某些非均相贵金属催化剂上的H物种吸附。新设计的双壁长单元给出了清晰的INS光谱，弹性散射较少。具有不同粒径的Pt，Pd和Rh金属纳米颗粒的三种氧化铝负载的金属催化剂在强度和能带分布方面表现出不同的INS光谱。对金属纳米颗粒和氧化铝表面上的H物种的观察揭示了它们的性质。另外，观察到Pd纳米颗粒中存储的H原子为氢化钯。相反，发现由炭黑负载的Pt催化剂上的H物质强烈吸附在碳载体上。这些H物种的性质取决于贵金属和载体材料的性质。