The polyoxometalate [PMo12O40](3-) (POM) has been deposited onto high surface area nano-SnO2 using a polycation. The POM surface coverage recorded was approximately 17 times higher than that achieved on planar substrates using the same method, reducing considerably the time needed to assemble conducting films suitable for optical applications such as electrochromism. The immobilisation of the analogous tungstate [PW12O40](3-) onto a nano-TiO2 semiconductor electrode demonstrates the versatility of this approach, and underscores potential applications using a large combination of polyoxomolybdates or polyoxotungstates with various metal oxide films.