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

Nanotubular Fe 2 O 3 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 Fe 2 O 3 nanotube arrays that survive HTC for the first time. By introducing a ZrO 2 shell on hydrothermal FeOOH nanorods by atomic layer deposition, subsequent high‐temperature solid‐state reaction converts FeOOH‐ZrO 2 nanorods to ZrO 2 ‐induced Fe 2 O 3 nanotubes (Zr‐Fe 2 O 3 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‐Fe 2 O 3 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).