Design and fabrication of sandwich-structured α-Fe2O3/Au/ZnO photoanode for photoelectrochemical water splitting

Abstract

α-Fe2O3/Au/ZnO hetrostructured thin films were fabricated using chemical spray pyrolysis technique and implemented as photoanode for photoelectrochemical (PEC) water splitting. Photoactivity of α-Fe2O3/Au/ZnO electrodes for PEC water oxidation under solar radiation was efficiently improved as compared to that for α-Fe2O3, α-Fe2O3/Au and α-Fe2O3/ZnO electrodes. The α-Fe2O3/Au/ZnO photoanode displayed a significant increase in photocurrent density of 250µA/cm2, as compared to α-Fe2O3 (photocurrent density~27µA/cm2), at 0.5V vs. SCE in 0.5M NaOH under AM 1.5G illumination indicating enhanced optical absorption and charge transportation. The presence of Au layer favored the charge transfer from α-Fe2O3 to ZnO via high energy coupled surface plasmons. The charge transfer kinetics was further improved by tuning of the surface plasmon resonance (SPR) band of Au nanoparticles (NPs) using electric field assisted spray pyrolysis. The maximum photocurrent density of 500µA/cm2 (at 0.5V vs. SCE) was obtained for α-Fe2O30.5kV/Au/ZnO electrode. The optimized design using Au sandwiched layer between two different band gap semiconductors with creation of different hetrojunctions (α-Fe2O3/ZnO and ZnO/Au) presented a configuration with enhanced optoelectronic properties, which is highly useful for PEC water splitting.