Improvement of the Water Oxidation Performance of Ti, F Co-modified Hematite by Surface Modification with Co(salen) Molecular Cocatalyst

A promising integral modification method to solve the correlative drawbacks of hematite photoanode from the bulk to the surface was proposed. In this study, a new system was developed by combining Ti-doping and F-treatment in hematite nanorods, and finally modified with Co(salen) as a cocatalyst. Ti-doping dramatically enhanced the current density owing to the increase of conductivity, while F-treatment lowered the onset potential by forming F-Ti moieties on the surface of hematite nanorods. The loading of Co(salen) on the surface of hematite nanorods as a molecular catalyst further improved the photoelectrochemical performances of both the photocurrent and the onset potential. This complex structure of F-Ti-Fe2O3/Co(salen) acquired a current density of 3.02 mA/cm2 at 1.23 V vs. RHE under illumination, which was 6 times higher than that of pristine hematite. Compared to aggregated CoOx, which was derived from Co(salen) thermally treated, molecularly-dispersed Co(salen) was an efficient cocatalyst because its molecular structure generated a fluffy space, which provided more active reaction sites and promoted the water oxidation reaction kinetics.