Niobium Oxyhydroxide-Polyoxometalate Composite as an Efficient Proton-Conducting Solid Electrolyte

It is still challenging to develop new and low-cost proton-conductive solid electrolytes using a simple synthetic procedure. Herein, a new proton-conducting material was synthesized for the first time through a sol-gel method by merging niobium oxyhydroxide with polyoxometalate (POM). NbO2(OH)-PW12 exhibited higher proton conductivity than that of niobium oxyhydroxide with varying humidity. Additionally, the molar ratio of Nb:{PW12} played a vital role in the proton conductivity and, when the molar ratio of Nb:{PW12} was 67:1, the material showed the maximum proton conductivity with a value of 7.25mScm(-1) at 77 degrees C under 97% RH, which was 10000 times higher than that of niobium oxyhydroxide. To the best of our knowledge, this is the first niobium-oxyhydroxide-based intrinsic proton conductor with such high proton conductivity below 100 degrees C. The kinetics study suggested that the proton conduction mechanism of NbO2(OH)-PW12 might follow the Grotthuss mechanism.