Gasochromic based optical hydrogen sensors have attracted much attention as normal temperature sensors. The behaviors of the hydrogen diffusion largely affect the reaction process and the sensitivity. However, few researches focused on the influence of hydrogen diffusion in gasochromic films. Here, we report a method to pre-split the H-2 molecule and separate the hydrogen molecule and hydrogen atom diffusion process by deposition of porous PdCl2/SiO2 catalyst films on WO3. The response time of WO3 at 844 Pa H-2 partial pressure reduced from 800 s to 200 s. The stability of WO3 film was largely improved to be more than 160 cycling lifetime. A validation experiment was designed and proved the diffusion of the hydrogen atom and the two-step model of H-2 reaction on WO3 films, on the basis of which the diffusion coefficient of the hydrogen atom has been estimated. Moreover, the PdCl2 doping SiO2 catalyst exhibits substrate versatility, which can also coat on the nano-structured WO3. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.