Enhanced Photoelectrochemical Water Oxidation Performance in Bilayer TiO2/α-Fe2O3 Nanorod Arrays Photoanode with Cu : NiOx as Hole Transport Layer and Co-Pi as Cocatalyst

Efficient charge transfer and excellent surface water oxidation kinetics are key factors in determining the photoelectrochemical (PEC) water splitting performance in photoelectrodes. Herein, a bilayer TiO2/alpha-Fe2O3 nanorod (NR) arrays photoanode was prepared with deposited Cu-doped NiOx (Cu : NiOx) hole transport layer (HTL) and Co-Pi oxygen evolution reaction (OER) cocatalyst for PEC water oxidation. The hierarchical TiO2/alpha-Fe2O3 composite obtained by a secondary hydrothermal process exhibited an inapparent bilayer structure by embedding the underlayer TiO2 NR arrays at the bottom part of the post-grown alpha-Fe2O3 NR arrays. The underlayer TiO2 NRs acted as an effective shuttling pathway for transferring photoelectrons generated in the upper hematite light absorber layer. A p-type inter-Cu : NiOx HTL was introduced to form a build-in p-n electric field between Cu : NiOx and alpha-Fe2O3 NRs, which improved the hole extraction from alpha-Fe2O3 to Co-Pi OER catalyst. As expected, the as-engineered TiO2/alpha-Fe2O3/Cu : NiOx/Co-Pi photoanode displayed an excellent photocurrent density of 2.43 mA cm(-2) at 1.23 V versus the reversible hydrogen electrode (V-RHE), up to 4.05 and 2.23 times greater than those of the bare alpha-Fe2O3 (0.60 mA cm(-2)) and TiO2/alpha-Fe2O3, respectively. The results demonstrate that the bottom-up engineering of electron-hole transport channels and cocatalyst modification is an attractive maneuver to enhance the PEC water oxidation activity in hematite and other photoanodes.

Automated summary

Efficient charge transfer and excellent surface water oxidation kinetics are crucial for determining the performance of photoelectrodes in PEC water splitting. In this study, a bilayer TiO2/alpha-Fe2O3 nanorod arrays photoanode was prepared with Cu-doped NiOx HTL and Co-Pi OER cocatalyst, achieving a significantly enhanced photocurrent density.