High-crystalline and high-aspect-ratio hematite nanotube photoanode for efficient solar water splitting

Abstract

Hematite (ɑ-Fe2O3) nanotube arrays with high aspect ratio and well-defined crystalline structures are highly attractive for photoelectrochemical water splitting. However, their design and fabrication remain a great challenge resulted from the poor thermal stability. Herein, we demonstrate that the high-crystalline Fe2O3 nanotube arrays with average length of 2 μm and high density of 2.5×107 tubes/cm2 could survive extended calcination temperatures up to ∼800 °C without any sintering. Owing to the well-oriented tubular structure, high light absorption and rich surface defects, this Fe2O3 nanotube photoanode exhibits a significantly improved PEC activity for water oxidation, and the photocurrent could be achieved up to 1.2 mA cm−2 at 1.23 V (vs. reversible hydrogen electrode, RHE). The decoration of FeOOH/NiOOH dual-cocatalysts not only caused a negative shift on onset-potential (170 mV), but also increased the photocurrent density up to 2.0 mA cm−2 (1.23 VRHE), which is the highest value among the reported hematite nanotube photoanodes.