Tuning the ion permeability of an Al2O3 coating layer on Fe2O3 photoanodes for improved photoelectrochemical water oxidation. Issue 18 (18th April 2017) - Fan, Zhongwen
Abstract : An ion-permeable Al2 O3 overlayer can enhance the injection efficiency ( Φ inj ) of Ti-Fe2 O3 photoanodes up to 95%. Abstract : Inevitable surface defects on α-Fe2 O3 photoanodes, a promising candidate for photoelectrochemical (PEC) water splitting with excellent stability and absorption in the visible light region, greatly limit their PEC performance for water oxidization. Surface modification is an effective strategy to decrease the negative effects of the surface defects. However, a challenge in understanding the nature of surface modification still remains. Here, we found that an ion-permeable Al2 O3 coating layer can effectively prevent oxygen diffusion to the photoanode surface, thus suppressing the back reaction from oxygen reduction. The ion-permeable Al2 O3 leads to ineffective surface state passivation due to the possible interface corrosion effect of OH − ions that decrease the interactions between Al2 O3 and Fe2 O3 . In contrast, the ion-impermeable Al2 O3 layer exhibits strong interactions with Fe2 O3 and is mainly responsible for both surface state passivation and back reaction suppression, improving the photocurrent onset potential. Our results indicated that the modification of ion-impermeable passivation layers is a potential effective strategy to enhance the PEC performance.