Publication

Journal	PHYSICAL CHEMISTRY CHEMICAL PHYSICS
Volume (Issue)	22(46)
Page(s)	27450 - 27457
Title of proceedings	PHYSICAL CHEMISTRY CHEMICAL PHYSICS
DOI	10.1039/d0cp04954a

Elemental doping of hematite has been widely performed to improve its mobility, electrical conductivity as well as to suppress electron-hole recombination in photoelectrochemical applications. When hematite is doped with high titanium concentrations, above 5\%, pseudobrookite layers may be formed as overlayers leading to improved photocurrent while further doping beyond 15\% could lead to the formation of a titania overlayer which has an effect of suppressing photocurrent. In this study, we observed that doping hematite with titanium improves photocurrent, reaching a maximum of 1.83 mA cm(-2) at a titanium concentration of 15\%, the highest achieved photocurrent with spin coating method. Further titanium incorporation to 20\% resulted in a decrease of the photocurrent. XRD measurements shows that a Fe2TiO5 layer formed at 15\% Ti concentration which resulted in the observed increase in photocurrent while a reduction in photocurrent at 20\% Ti concentration could have resulted from the formation of a TiO2 layer. Analysis of the transient absorption spectroscopy data was achieved using a four-component sequential analysis scheme in the Glotaran software. We observed major doping concentration dependent lifetimes in the tau(3) and tau(4) values where the 15\% doped samples had the slowest recombination rates. We also observed a blueshift in the spectra with increasing doping concentration, suggesting the occurance of the Burstein-Moss effect. This work shows that doping hematite with titanium leads to structural changes of the photoanodes at Ti concentrations of over 10\%, in addition to the well documented conductivity enhancement.