Tin oxide coating by nonvacuum-based mist chemical vapor deposition on stainless steel separators for polymer electrolyte fuel cells

Coating of stainless steel (SUS) separators of polymer electrolyte fuel cells (PEFCs) with tin oxide (SnO2) thin films by nonvacuum-based mist chemical vapor deposition technology has been proposed for cost-effective and highly endurable cells. Fluorine-doped SnO2 resulted in low electrical resistivity of the films and high corrosive resistance of the SnO2-coated SUS separators. The novel pretreatment of SUS substrates successfully enhanced the strength of SnO2 adhesion to the substrates. The PEFCs composed of the SnO2-coated SUS separators showed stable operation for more than 1000 h without the SnO2 films peeling off of or severe degradation of the separators. The maximum power density achieved by using the SnO2-coated SUS separators was ~0.3 W/cm2, which was expected to be improved by optimizing the fabrication processes of the SnO2 thin films so that the series resistance of the SnO2/SUS can be sufficiently low.