 For applications with liquid electrolytes, such as the zinc-air battery or the alkaline fuel cell, the dry mixture method is used.In acidic electrolytes the catalysts are usually precious metals like platinum, ruthenium, iridium and rhodium.In alkaline electrolytes, like zinc-air batteries and alkaline fuel cells, it is usual to use less expensive catalysts like carbon, manganese, silver, nickel foam or nickel mesh.