Porous V2O5 ion-storage film as the counter electrode of electrochromic WO3 film: Optimization via Response Surface Methodology (RSM)

Electrochromic glass, one of the green energy-saving building materials, get more and more attention. The advancement of efficient ion storage film become a hot topic of research. The porous V 2 O 5 ion-storage film was prepared by sol-gel method using polyethylene glycol (PEG) as the pore-former. The peak current of porous V 2 O 5 films heated at 300 °C increased substantially due to the volatility temperature of PEG at 285 °C. The mutual effects of the PEG content, heat treatment temperature, and heat treatment time on the structure and electrochromic properties of porous V 2 O 5 film were investigated by the response surface method (RSM). The results show that the influence extent on ion storage is: heat treatment temperature > PEG content > heat treatment time. Under optimized process parameters of PEG content 6.2 g/100 mL sol, heat treatment time 4 h, heat treatment temperature 310 °C, the porous V 2 O 5 film exhibited excellent ion storage capacity (87.28 mC·cm −2 ). The electrochromic device (ECD) with optimized porous V 2 O 5 ion-storage film as the counter electrode of electrochromic WO 3 film has been successfully assembled, which shows fascinating performance with high optical contrast (87.8% at 550 nm) and fast response time (bleaching/coloring: 4.5/3.7 s). Graphical Abstract Highlights The porous V 2 O 5 ion-storage films were prepared by sol-gel method with PEG as pore-former. Response surface methodology (RSM) was applied to optimize the process parameter. The sequence of the effect of the ion storage capacity is heat treatment temperature > PEG content > heat treatment time. Electrochromic devices (ECD) was assembled with porous V 2 O 5 film as the counter electrode of WO 3 film.