Adsorption of hydrogen and hydrogen–containing gases on Pd– and Ag–single atoms doped on anatase TiO2 (1 0 1) surfaces and their sensing performance

Abstract

The Pd– and Ag–doped anatase TiO2 (1 0 1) surfaces were investigated and the binding energies of single atom of Pd (−2.15 eV) and Ag (−2.38 eV) on the anatase (1 0 1) surfaces, respectively denoted as Pd/TiO2 and Ag/TiO2, were obtained. Binding sites for Pd and Ag atoms toward the TiO2 surface atoms are three atoms (Ti5C and two O2C atoms) and two O2C atoms of the TiO2 (1 0 1) surface, respectively. Due to adsorptions of H2 and hydrogen–containing (H2O, NH3, and CH4) gases on the Pd/TiO2 and Ag/TiO2, adsorption abilities on the Pd/TiO2 and Ag/TiO2 are in decreasing orders: NH3 > H2O > H2 > CH4 and NH3 > H2O > CH4 > H2, respectively. Mulliken–charge transfers from the Pd and Ag atoms to adsorption atoms of the anatase TiO2 (1 0 1) surface and the adsorption of hydrogen and hydrogen–containing gases to the Pd/TiO2 and Ag/TiO2 were observed. The Pd/TiO2 and/or Ag/TiO2 have high potentials to be NH3 sensing materials based on the electric conductivity measurement. The Pd/TiO2 has high potential to be CH4 sensing device based on the electric conductivity and surface charge measurements.