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Sonochemical-Assisted In Situ Electrochemical Synthesis of Ag/α-Fe2O3/TiO2 Nanoarrays to Harness Energy from Photoelectrochemical Water Splitting

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journal contribution
posted on 24.07.2018 by Ibrahim Khan, Ahsanulhaq Qurashi
Numerous protocols in heterostructure engineering hold promise for effectively improving the optical properties of nanomaterials for energy-harvesting applications. In this work, we successfully fabricated Ag/α-Fe2O3/TiO2 heterostructures via electrochemical anodization assisted by pulse sonication. The morphological features of the silver (Ag) deposited on α-Fe2O3/TiO2 showed a layered distribution of the α-Fe2O3 nanoparticles (NPs) over the TiO2 nanotube arrays (NTAs), whereas Ag existed in a pseudocubical form. X-ray diffraction (XRD) patterns and X-ray photoelectron spectrometer (XPS) analysis validated the formation of α-Fe2O3 and anatase TiO2 crystalline phases and Ag/α-Fe2O3/TiO2 heterostructure. The diffuse reflectance spectroscopy (DRS) UV–vis spectroscopy results displayed a gradual decrease in the band gap with enhanced absorption in the visible region of the spectrum due to optically active heterostructure formation in the order Ag/α-Fe2O3/TiO2 (470 nm) > α-Fe2O3/TiO2 (424 nm) > TiO2 (386 nm). The DRS absorption spectrum of Ag/α-Fe2O3/TiO2 also exhibits a characteristic plasmon shoulder of Ag at ∼420 nm. The photocurrent density of Ag/α-Fe2O3/TiO2 (2.59 mA/cm2) is almost 2.5- and 5-fold higher than that of α-Fe2O3/TiO2 (1.05 mA/cm2) and pristine TiO2 (0.54 mA/cm2), respectively, which can be related with the plasmonic behavior of Ag and lower band gap of α-Fe2O3. The results of electron impedance spectroscopy (EIS) analysis also showed facile charge transfer in the same order observed using UV–vis spectroscopy. These results demonstrate the effectiveness of the in situ electrochemical protocol to fabricate tunable heterostructures for efficient solar-driven water splitting.