A comparison between proton and hydrogen chemical diffusion coefficients of titanium oxide films

Abstract

Proton and hydrogen diffusion in titanium oxide thin films is of significant interest because of its importance in barrier, sensor, and catalytic coating applications. In this study, a novel method based on potential–pH response measurement was used to determine proton chemical diffusion of titanium oxide thin films. This technique, based on the model of diffusion-controlled proton transport at the oxide surface, measures the potential–pH response drift as a stepwise increase and decrease in pH (i.e., pH = 4, 7, and 10) of buffer is generated in a thermostatic measurement setup. The proton chemical diffusion coefficient for titanium oxide films obtained from this method was 10–17 cm2/s, about two orders smaller than the hydrogen chemical diffusion coefficient (10–15 cm2/s) obtained from the conventional electrochemical permeation technique.