Surviving High‐Temperature Calcination: ZrO2‐Induced Hematite Nanotubes for Photoelectrochemical Water Oxidation

Nanotubular Fe2O3 is a promising photoanode material, and producing morphologies that withstand high‐temperature calcination (HTC) is urgently needed to enhance the photoelectrochemical (PEC) performance. This work describes the design and fabrication of Fe2O3 nanotube arrays that survive HTC for the first time. By introducing a ZrO2 shell on hydrothermal FeOOH nanorods by atomic layer deposition, subsequent high‐temperature solid‐state reaction converts FeOOH‐ZrO2 nanorods to ZrO2‐induced Fe2O3 nanotubes (Zr‐Fe2O3 NTs). The structural evolution of the hematite nanotubes is systematically explored. As a result of the nanostructuring and shortened charge collection distance, the nanotube photoanode shows a greatly improved PEC water oxidation activity, exhibiting a photocurrent density of 1.5 mA cm−2 at 1.23 V (vs. reversible hydrogen electrode, RHE), which is the highest among hematite nanotube photoanodes without co‐catalysts. Furthermore, a Co‐Pi decorated Zr‐Fe2O3 NT photoanode reveals an enhanced onset potential of 0.65 V (vs. RHE) and a photocurrent of 1.87 mA cm−2 (at 1.23 V vs. RHE). Survival training: Hematite nanotube arrays (Fe2O3‐NTs) surviving high‐temperature calcination were prepared by a solid‐state reaction between an FeOOH nanorod core and a ZrO2 shell. Their greatly improved photoelectrochemical water oxidation performance originates from their nanostructured morphology and shortened charge collection distance (see picture; W=depletion layer width).