Low‐temperature catalytic activity of CO oxidation by uni‐size Pt₃₀ cluster disks bonded to silicon substrate

Abstract

We investigated catalytic activity of CO oxidation by monatomic‐layered cluster disks, Pt30, bonded to a silicon substrate by means of ultrahigh‐sensitive temperature‐programmed desorption (TPD) mass‐spectrometry. It was found in the repeated TPD measurements with various reactant‐exposure amounts that this cluster‐substrate system possesses high ability of low‐temperature reductive activation of oxygen molecules, which is the rate‐determining step of the CO oxidation. This high‐performance is explained in terms of negative charges accumulated at a subnano interface between the cluster disk and the silicon substrate surface.

Systematic study on novel catalytic activity of CO oxidation driven by strong electronic interaction between the monatomic-layered Pt30cluster disk and the Si substrate

“…The details of the experimental apparatus have been reported elsewhere. 21,23,24 The Pt cluster ions, Pt N + , were produced by means of a magnetron-sputtering device, 8 and a desired cluster size was selected out by passing through a quadrupole mass filter. Both their kinetic energies and ion-beam diameter were reduced in collision with cold He gas at 100 K. The lowtemperature uni-size Pt N + were allowed to collide onto the (111)-7 Â 7 reconstructed surface of a Si substrate 25 at 300 K at a collision energy of 1 eV per Pt atom and at a pressure less than 5 Â 10 À8 Pa so as to bond the uni-size Pt N to the substrate as the monatomic-layered cluster disks.…”

“…cluster disks bonded to the silicon surface as a benchmark reaction of the catalysis. 21 This cluster-substrate system possesses high ability of low-temperature reductive activation of molecular oxygen, which is one of the critical steps of the CO oxidation. 22 In the present study, temperature-programmed desorption (TPD) measurements were repeated for a given cluster sample with a systematic change in the adsorption amounts of the reactants, O 2 and CO, to rotate the catalytic cycle, so that individual contributions of the two reactions, the CO oxidation by molecular and atomic oxygen, were derived quantitatively.…”

Novel catalytic functions induced by charge accumulation at subnano interface between unisize metal cluster disk and semiconductor surface

“…The cluster catalyst sample was prepared in a similar manner to those described in the previous section; 500 nC of unisize Pt 30 + was irradiated onto a circular area (8 mm in diameter) of the Si(111) surface . The substrate surface was terminated with hydrogen by irradiating a hydrogen beam.…”

“…The cluster catalyst sample was prepared in a similar manner to those described in the previous section; 500 nC of unisize Pt 30 + was irradiated onto a circular area (8 mm in diameter) of the Si (111) surface. [17][18][19] The substrate surface was terminated with hydrogen by irradiating a hydrogen beam. The cluster catalyst was cleaned by repeated burning of residual adsorbates at 620 K with 18 O 2 supplied at 105 K until the 13 C 16 O 18 O + intensity reached a background limit.…”

“…The geometry and the charge distribution of the cluster were measured by means of scanning–tunneling microscopy and spectroscopy (STM / STS) . The catalytic performance driven by the accumulated electrons was investigated for thermal oxidation of CO as a benchmark reaction of the catalysis by means of temperature‐programmed desorption (TPD) mass spectroscopy . It was found that this cluster‐substrate system has a higher catalytic activity of the CO oxidation driven by negatively charged O 2 than the Pt clusters supported on the MgO thin film and a similar performance to the (111) surface of a bulk Pt single crystal regardless of its finiteness.…”