High Proton Conductivity in Anodic ZrO2/WO3 Nanofilms

摘要

Anodization of the valve metals Al, Ti, Zr, Nb, Hf, Ta, and W leads to formation of barrier-type (compact) or self-organized porous-type anodic oxide films, depending on the electrolytes used. The oxide films formed are dielectrics or semiconductors with useful properties that make them of great interest for many applications, including solid electrolytic capacitors, solar cells, photocatalysis, electrochromic devices, and self-cleaning materials. Here we report the first example of an anodic oxide with high proton conductivity below 200 °C. Proton-conducting thin films are promising electrolytes for solid-oxide fuel cells that operate at intermediate temperatures (100-400 °C) and other electrochemical devices. Intermediate-temperature fuel cells have several advantages over polymer electrolyte fuel cells, which operate below 100 °C, under fully hydrated conditions. The former type allows the use of nonprecious-metal electrocatalysts and hydrocarbon fuels'61 and facilitates simpler module assembly by means of anhydrous proton conductors.