Catalytic combustion sensors are widely used for H-2 gas sensing because they use a simple sensing mechanism and have high chemical, thermal, and mechanical durability by virtue of their simple structure. In this study, Pd, Pt, and Pd-Pt-loaded TiO2 thin films were prepared. Their respective capabilities as H-2 gas combustion sensors were investigated. The TiO2 thin films were prepared using sol-gel method on a glass substrate. Then Pd and/or Pt was loaded on them using photocatalytic deposition. H-2 gas sensing was assessed at 300 degrees C by measuring the sample resistance under H-2 gas (3-100%) and air flow conditions. A Pd-Pt step-by-step loaded sample showed higher sensitivity than either a Pd or Pt single-loaded sample for H-2 concentrations of less than 30 vol%. Scanning transmission electron microscopic (STEM) observation revealed its structure: Pt fine particles deposited selectively on the Pd particles pre-deposited on the TiO2 surface. The large surface area of the catalyst and the synergetic effect of Pd and Pt are expected to contribute to the catalytic activity. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.059212jes] All rights reserved.