Photoelectrochemical water oxidation on PbCrO4 thin film photoanode fabricated via Pechini method: Various solution-processes for PbCrO4 film synthesis

Abstract

Abstract PbCrO4 thin film photoanode was fabricated by utilizing various solution-processes (precipitation, solution-combustion, sol-gel, and the Pechini methods) and its photocatalytic activity for photoelectrochemical water oxidation was characterized. During film formation, secondary phases such as Pb2CrO5, Pb5CrO8, and Cr2O3 were easily formed owing to the incomplete oxidation of Cr(III) in the precursor. The Pechini method inherently suppressed the formation of the secondary phase, whereas for the other methods optimization of the composition of the precursor for the solution-processes or the electrochemical removal of Cr2O3 were required in order to form a pure monoclinic PbCrO4 film. The photoactivity of the PbCrO4 films fabricated with the various solution-processes was characterized in conjunction with the film properties such as the morphology, crystal structure, and light absorbance. The low film coverage of PbCrO4 fabricated via the precipitation and solution-combustion methods resulted in low light absorbance, and consequently, low photoresponse whereas PbCrO4 prepared by the sol-gel and Pechini methods was photoresponsive. For water oxidation, only PbCrO4 from the Pechini method exhibited a reasonable photoresponse (0.57 mA/cm2 at 1.23 V vs RHE under 100 mW/cm2), whereas the photoacitivity of PbCrO4 from sol-gel method was deteriorated due to surface recombination of the photogenerated carriers. The photoactivity PbCrO4 from the Pechini method could be improved further to 0.91 mA/cm2 by decorating with a Co-Pi cocatalyst to enhance the kinetics of the water oxidation reaction. Co-Pi decoration also improved the faradaic efficiency for the water oxidation, which was roughly estimated from scanning electrochemical microscopy. However, the notable photoactivity of PbCrO4 deteriorated rapidly due to the photodegradation.