Hydrogen Tungsten Bronze

Introduction

Hydrogen tungsten bronze(HxWO₃，0≤x≤1) is non stoichiometric compound, it has ring channel and special space tunnel structure. This structure is useful for disembedding and exchange for ion, thus makes it capable of offering and accepting proton.

Proton exchange membrane fuel cell (PEMFC) has advantages of low reacting temperature, high power density, high efficiency and no pollution. It is being widely used in portable power supply, dynamical power and power station. Traditional catalyst uses Pt as main content, which is quite expensive. So adding auxiliary catalyst is an effective method to lower the using amount of Pt and promote its catalytic activity. Hydrogen tungsten bronze as auxiliary catalyst to combine with Pt, the proton will accelerate the oxygen reduction of Pt by offering, by accepting proton can accelerate the oxygen catalytic of Pt to methyl alcohol. As a result, it has wide application broad as PEMFC.

Preparation

1) APT (NH₄)10(H₂W₁₂O₄₂)7H₂O is decomposed to (NH₄ )10(W₁₂O₄₁)5H₂O under heating to 100 ～200 ℃.
2) (NH₄ )10(W₁₂O₄₁)5H₂O keeps decomposing to (NH₄)_0.33WO₃ under 200-250 ℃.
3) Under 250-575 ℃, (NH₄)_0.33WO₃ converts into H_0.33WO₃ and WO₃.
Among which (NH₄ )xWO₃ can be decomposed into HxWO₃ under 150-350 ℃ with change in crystalline structure, chemical equation is:
(NH₄)xWO₃=HxWO₃+xNH₃(g).