Hafnium boosts charge carrier dynamics in hematite for improved solar water splitting

The work demonstrates a three-fold increase in photoelectrochemical efficiency of hematite nanorods as a result of the combination of Hafnium surface doping and the incorporation of a ZrO2 underlayer on FTO. While the ZrO2 layer reduced the electron loss from the back-injection into the FTO contact support, Hafnium surface doping did not significantly alter the hematite lattice structure. But rather, Hafnium induced nanorod diameter reduction from 32 +/- 2 and 26 +/- 2 nm, with a consequent increase in the active surface area. The linear sweep voltammetry measurements with 100 mW cm-2 illumination in a 500 nm photoanode thickness showed a photocurrent density of 2.07 mA cm-2 at 1.23 V in a reversible hydrogen electrode (RHE). The value contrasts with the bare hematite rods (0.75 mA cm-2), highlighting the photoanode design's role in improving solar power hydrogen production.