Origin of the High Selectivity of the Pt-Rh Thin-Film H2Gas Sensor Studied by Operando Ambient-Pressure X-ray Photoelectron Spectroscopy at Working Conditions

Ryo Toyoshima, Takahisa Tanaka, Taro Kato, Ken Uchida, Hiroshi Kondoh

Research output: Contribution to journalArticlepeer-review

Abstract

The Pt-Rh thin-film sensors exhibit excellent sensitivity and selectivity for H2 gas detection. Here, we studied the mechanism of highly selective detection of H2 by the Pt-Rh thin-film sensors with ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) measurements at working conditions, which were paralleled with electric resistivity measurements. The elemental composition and chemical state of surface Pt and Rh drastically change depending on the background gas environments, which directly link to the sensor response. It is revealed that surface segregated Pt atoms accelerate dissociative adsorption of H2, resulting in a reduction of the sensor surface and then a decrease of electric resistivity of the film, whereas a thin oxidized Rh layer blocks dissociation of the other reducing agent, that is, NH3. This is supported from the adsorption energetics obtained by the density functional theory (DFT) calculations.

Original languageEnglish
Pages (from-to)8546-8552
Number of pages7
JournalJournal of Physical Chemistry Letters
Volume13
Issue number36
DOIs
Publication statusPublished - 2022 Sep 15

ASJC Scopus subject areas

  • Materials Science(all)
  • Physical and Theoretical Chemistry

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