Photoelectrochemical properties of butane reduced flame‐treated Zr‐doped hematite thin films

In this research, Zr‐doped hematite thin films were prepared by a simple and highly scalable liquid phase deposition method, and their photoelectrochemical (PEC) properties were investigated. The samples were post‐heat treated using a butane reduced flame. PEC studies revealed that both Zr‐doping and flame‐treatment enhanced the performance of the hematite photoanodes. The photocurrent densities of the samples were considerably increased upon flame‐treatment, that is, about 3.5 times for a 4% Zr‐doped sample. The highest photocurrent density at 1.23 V versus reversible hydrogen electrode (RHE) was obtained, about 0.50 mA cm−2 for the 4% Zr‐doped sample, about five times higher than the undoped sample. The Mott–Schottky measurements revealed that the donor charge carrier density for the 4% Zr‐doped sample was increased fivefold upon flame‐treatment from 2.49 × 1019 to 1.38 × 1020 cm−3. The optical investigations showed that the optical band gap energy values depend on the level of Zr‐doping, and the sample with 4% Zr‐doping showed the lowest band gap energy value, about 1.82 eV. The mechanism behind the effectiveness of the flame‐treatment was investigated and attributed to the oxygen vacancy formation upon flame‐treatment. The formation of oxygen vacancies activates the donor doping, and as a result, the charge carrier density increases. In general, butane reduced flame‐treatment as a simple and effective strategy can be used as a post‐heat treatment to boost the PEC properties of hematite thin films.