Ultrathin alumina wrapped TiO2 nanorods for enhance photoelectrochemical performance via atomic layer deposition method

Abstract

In the present study, a series of Al2O3 (alumina) ultrathin film coated titanium dioxide nanorods (TONRs) were fabricated on F-doped SnO2 (FTO) glass for enhancing the photoelectrochemical (PEC) performance. Thin Al2O3 coating layers of different thicknesses were prepared by using five, 10, 15, 20, 35 and 75 cycles of the atomic layer deposition (ALD) method with accurate control of the thickness. Each cycle of the ALD method deposits a layer of Al2O3 approximately 0.08 nm thick. The microstructure, surface morphology, chemical composition, optical and PEC properties of the Al2O3 coated TONRS (AO-TONRs) were compared to uncoated TONRs. The TONRs coated with Al2O3, using 35 cycles of the ALD method (AO35-TONR) had the best PEC performance, the lowest electrochemical impedance, and the highest photocurrent density compared to the other AO-TONRs and uncoated TONR. The AO35-TONR had the highest photocurrent density (~80.3 μA/cm2) that was 7.4 times higher than that of the uncoated TONRs (~10.8 μA/cm2). The improved PEC performance was because of the surface passivation effect and energy band field passivation effect achieved by introducing the Al2O3 coating layer of the correct thickness. In conclusion, the method described in the present study provides a series of simple and effective applications for enhancing the performance of photoelectrochemical and optoelectronic devices.