Engineering carrier density at TiO2 nanotube metasurface with hole reservoir for Enhanced Photo-electrocatalysis

Abstract

Solar-driven photo-electrocatalysis using semiconductor photoelectrodes offers a promising advance for sustainable and environmental-friendly energy utilization technology. At the same time, the inherent drawbacks of TiO2-based materials, such as limited light absorption and low carrier density, limit their practical applications. Engineering nanoarchitectured photocatalysts is an alternative route tailoring their optical properties, thus increasing light-harvesting efficiencies. Herein, combining electrochemical reduction and selective interface decoration, FeOOH modified reductive TiO2 nanotube arrays (FeOOH@R-TiO2 NTA) with enhanced carrier density and improved photocatalytic activity are developed. The well-aligned NTA endows the metasurface with enhanced light absorption in the photocatalyst. Notably, the electrochemical reduction induces Ti3+ states increases free electron density and conduction band tail (defects levels); the modified FeOOH nano blocks act as hole reservoirs to significantly improve the hole-electron separation. The donor density of 4.57 × 1020 cm−3 is recorded at FeOOH@R-TiO2 NTA metasurface, showing 3 orders of magnitude higher than that of calcinated TiO2 (6.62 × 1017 cm−3). The metasurface is applied to oxidize benzyl alcohol triggered by a LED light irradiation, demonstrating a proof-of-concept application. The improved light absorption, carrier separation, and donor density facilitate the photoelectrochemical oxidation performance of FeOOH@R-TiO2 NTA.