Accelerated and durable hydrogen gasochromism in mesoporous Pt–WO₃ films enabled by an ICP-CVD PTFE-like (CF₂)_n overlayer

A conformal polytetrafluoroethylene (PTFE)-like fluorocarbon [(CF₂)ₙ] overlayer is deposited onto mesoporous Pt/WO₃ films via inductively coupled plasma chemical vapor deposition (ICP-CVD), yielding simultaneous improvements in coloration kinetics and cycling stability. Under an air-filled chamber directly switched to 4% H₂/Ar (1000 sccm), the 90% coloration time ( \({t}_{\text{c},90}\) $t_{\text{c},90}$ ) decreases from 22.2 s for Pt/WO₃ to 15.5 s for Pt/WO₃@(CF₂)ₙ. When the chamber is first purged with Ar (oxygen-free), \({t}_{\text{c},90}\) $t_{\text{c},90}$ further shortens to 4.6 s at 4% H₂/Ar, while the 90% bleaching time ( \({t}_{\text{b},90}\) $t_{\text{b},90}$ ) remains below 35 s over 0.1–4% H₂/Ar. Notably, Pt/WO₃@(CF₂)ₙ maintains nearly constant optical modulation over 80 coloration/bleaching cycles, whereas the uncoated film shows progressive degradation. We attribute these enhancements to preferential H₂ transport through the fluorocarbon layer relative to O₂, mitigating oxygen competition, and to interfacial Pt–CFₓ interactions that facilitate H₂ dissociative chemisorption and spillover to WO₃.