Dual‐Axial Gradient Doping (Zr and Sn) on Hematite for Promoting Charge Separation in Photoelectrochemical Water Splitting

Abstract One of the crucial challenges to enhance the photoelectrochemical water‐splitting performance of hematite (α‐Fe 2 O 3 ) is to resolve its very fast charge recombination in bulk. Herein, we describe the design and fabrication of dual‐axial gradient‐doping on 1D Fe 2 O 3 nanorod arrays with Zr doping for x ‐axial and Sn doping for y ‐axial directions to promote the charge separation. This dual‐axial gradient‐doping structure fulfills the requirements of a greater electron‐carrier concentration for increasing conductivity as well as a higher charge‐separation efficiency across the dual‐axial direction of Fe 2 O 3 nanorods, ultimately showing an excellent photocurrent density of 1.64 mA cm −2 at 1.23 V vs. RHE, which is 26.3 times more than that of the bare Fe 2 O 3 . Furthermore, the remarkably improved photocurrent density, when comparing the uniform Zr‐doped Fe 2 O 3 nanorod arrays (1.0 mA cm −2 at 1.23 V vs. RHE) with dual‐axial gradient‐doped (Zr and Sn) Fe 2 O 3 nanorod arrays, highlights the additional charge‐separation effect resulting from gradient codoping of Zr and Sn. Hence, this promising design may provide guidelines for dual‐axial gradient doping into photoelectrodes to realize efficient PEC water splitting.