Spectrosopic and paramagnetic properties of molybdenum oxyhydroxide films electrochemically formed from the Keggin-type (PMo_12O_40)^3− complex

Molybdenum-containing films electrochemically deposited from an aqueous solution of 12-molybdphosphate (PMo 1 2 O 4 0 ) 3 - (denoted as PMo 1 2 ) have been characterized by x-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), and electron spin resonance (ESR) techniques. XPS and FTIR data indicate that electrolysis of PMo 1 2 leads to the formation of Mo-O-Mo linkage by condensation of the polyanions accompanied by decomposition of the phosphate moiety. The ESR spectrum of the deposited film exhibits an asymmetric signal with g ∼1.92, indicative of pentavalent molybdenum (d'). The feature of this signal is close to that for a MO V ion in the amorphous MoO 3 phase, but not in the PMo 1 2 framework. It is therefore suggested that the deposited film no longer has the Keggin structure PMo 1 2 , but consists of a continuous structure containing molybdenum oxide.

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