XPS studies on the Mo oxide-based coatings electrodeposited from highly saturated acetate bath

Abstract

The possibility to use highly saturated acetate bath to electrodeposit the mixed-phase materials containing Mo oxides has been investigated. The XRD characterization revealed that the as-deposited coatings are amorphous and consist only of MoO₂ and MoO₃ phases without traces of metallic Mo phase. This statement has been supported by XPS measurements, which reveal the presence of three different molybdenum oxidations states in electrodeposits: Mo⁴⁺, Mo⁵⁺ and Mo⁶⁺. It was found that the Mo⁶⁺ state prevails with 41% of total contribution, whilst Mo⁵⁺ and Mo⁴⁺ contribute to 28 and 31%, respectively. The deposits retain an amorphous structure up to 800°C; while molybdenum at this temperature is predominantly oxidized to the Mo⁶⁺ state (91%). These results, coupled to those of SEM and EDS, revealed that concentrated acetate bath could be used mainly for the formation of the mixed valence molybdenum oxide film unlike to the deposition of the metallic Mo phase.