Color-switchable phosphomolybdate-nickel nanofilm with superior optical modulation and long-term stability for electrochromic energy storage

Transition metal oxides and hydroxides have become highly required for their electrochromic properties and energy storage capabilities owing to their affordability, adaptable structure and exceptional endurance. However, they encounter notable obstacles in achieving substantial advancements in large-scale optical modulation and high coloring efficiency, mostly stemming from their limited electron conductivity and an inadequate number of reactive sites. Current study presents simple and scalable electrodeposition method for phosphomolybdate-nickel (NiHPMo 12 O 40 , PMo 12 -Ni) nanofilms with high purity and small nano-grain sizes ensuring efficient electrochemical and electrochromic performance. Specifically, the PMo 12 -Ni nanofilm has demonstrated superior transmittance (96.5 %), huge optical modulation (87.3 %), substantial increased coloration efficiency (114 cm 2  C −1 ) and stable optical memory with the decay of only 5.1 % up to 5000 s among other transition metal oxides reported to date. The PMo 12 -Ni nanofilm also exhibits excellent energy storage characteristics with high specific capacitance of 60.1 mF cm −2 at current density of 1.5 mA cm −2 . Consequently, the PMo 12 -Ni nanofilms can be consider as valuable candidates for modern electrochromic and energy storage applications.