Hematite Photoanode with Complex Nanoarchitecture Providing Tunable Gradient Doping and Low Onset Potential for Photoelectrochemical Water Splitting

Abstract
Over the past years, α-Fe2O3 (hematite) has re-emerged as a promising photoanode material in photoelectrochemical (PEC) water splitting. In spite of considerable success in obtaining
relatively high solar conversion efficiency, the main drawbacks hindering practical application at hematite are related to an intrinsically hampered charge transport and a sluggish kinetics of the oxygen evolution reaction on the photoelectrode surface.
In the present work, we report a strategy how to synergistically address both these critical limitations. Our approach is based on three key features that are applied simultaneously,
specifically i) a careful nanostrcuturing of hematite photoanode in the form of nanorods, ii) doping of hematite by Sn4+ ions by a controlled gradient, and iii) surface decoration of hematite by a new class of double hydroxide layered (LDH) OER co-catalysts based on Zn-Co LDH. All three interconnected forms of functionalization result in an extraordinary cathodic shift of the
photocurrent onset potential by more than 300 mV and a PEC performance that reaches a photocurrent density of 2.00 mA/cm2 at 1.50 VRHE