Erbium and titanium co-doped hematite nanorods. Structural, optical, and catalytic properties for enhanced water splitting

Herein, hydrothermally synthesized hematite nanorods (NRs) co-doped with erbium and titanium, using titanium tetrachloride and erbium(III) nitrate pentahydrate as the dopant sources, are presented. The effect of varied volumes of the erbium/titanium surface co-dopants on the morphology, structural, optical, and photoelectrochemical (PEC) properties of hematite NRs is investigated. The pristine hematite, 40 µL-Er, and 40 µL-Er/20 µL-Ti-doped NRs samples present a similar surface morphology of vertically aligned NRs. The NRs are randomly oriented with an increase in titanium dopant for the 40 µL-Er/30 µL-Ti-doped NRs and later coalesced for the 40 µL-Er/40 µL-Ti-doped NRs. The structural analysis based on X-ray diffraction and Raman analysis present a uniform, pure hematite phase for all the prepared NRs. The samples exhibit high photon absorbance with peaks in the 400-450 nm wavelength range of the visible spectrum. The 40 µL-Er/40 µL-Ti-doped NRs sample present the highest photocurrent density of 83.9 µA cm${}^{-2}$ at 1.4 V vs reversible hydrogen electrode (RHE) and is attributed to the lowest flat band potential (-0.76 V vs RHE) that enhances charge mobility at the electrode-electrolyte interface. These results reveal the facile erbium/titanium doping of hematite NRs as a viable strategy for enhancing their PEC water-splitting performance. (© 2023 The Authors. physica status solidi (a) applications and materials science published by Wiley‐VCH GmbH)