Stable free-standing aramid resin film containing vanadium pentoxide and new colour electrochromism of the film by electrodeposition of gold

Vanadium pentoxide (V₂O₅) was electrodeposited on a poly(p-phenylene terephtalamide) (PPTA)-film coated electrode. The cyclic voltammogram of the film had a reversible redox current peak. The film was dark green in the reduced state and yellow in the oxidized state. To obtain new colour, gold was further electrodeposited on the film. Not only the redox current peak but also a new redox current shoulder appeared in the cyclic voltammogram of the obtained film, and it exhibited a multicoloured electrochromism: blackish green ↔ dark green ↔ green ↔  bright red. The red colour in the oxidized state was first obtained for the V₂O₅ film. The new redox current shoulder and the colour were probably due to Au_yV₂O₅ partially formed during electrodeposition of the gold. The redox of the Au_yV₂O₅ was accompanied by egress and ingress of Li⁺ ions and the new colour change.