Inorganic additives hydrogen sulfates

The third form of inorganic sulfur - the sulfate variety - is realitively unimportant in energy conversion. Fresh coal contains very little sulfate its presence is usually indicative of a weathered (oxidized) feedstock. Additionally, sulfate may be formed to a minor degree from other types of sulfur by moderate heating of the feedstock, by reaction with the bound oxygen in that feed. This effect can even occur under a hydrogen atmosphere. ... 

The primary drawbacks of the Nafion membranes are poor conductivity at low relative humidities (and consequently at temperatures >100 C and ambient pressure) and large crossover of methanol in direct methanol fuel ceU (DMFC) applications. As a result, considerable efforts have been made in recent years to overcome these drawbacks. Peihaps the most widely employed approach is the addition of inorganic additives to Nafion m branes to yield organic/inorganic composite membranes. Three major types of inorganic additives that have been studied (zirconium phosphates, heteropolyadds, metal hydrogen sulfates and metal oxides) are reviewed in the following. 

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