Accelerated oxygen evolution kinetics on hematite by Zn2+ for boosting the photoelectrochemical water oxidation

Abstract

The sluggish oxygen evolution reaction (OER) kinetics on hematite (α-Fe2O3) has constrained the photoelectrochemical (PEC) performance for water oxidation. Considering the regulatory effect of Zn for electrocatalytic OER, the Zn doped α-Fe2O3 nanowire is successfully prepared and served as the photoanode for PEC water oxidation. The results reveal the theoretical overpotential for the limiting step (from OH* to O*) is decreased by ca. 320 mV after Zn doing, which indicates an incredibly improved catalytic performance of OER. The Zn doped α-Fe2O3 displays PEC performance improvement over the bare α-Fe2O3, photocurrent density increases up to 0.88 mA/cm2(1.23 VRHE, 1 M NaOH), which shows a 44-fold increase than the α-Fe2O3. Meanwhile, the onset potential also shifts negatively by 300 mV, which also agrees well with the decreased OER overpotential. This work provides a deep understanding of the role of Zn in the α-Fe2O3 photoanodes and the strategy could be extended to other photoactive systems.