Group IIIA doping in \textit{$\alpha $}-Fe$_{2}$O$_{3}$ for PEC hydrogen production

Among iron oxides, \textit{$\alpha $}-Fe$_{2}$O$_{3}$ is the most abundant on earth. Because it has a band gap of approximately 2 eV, it is stable and inexpensive to process, \textit{$\alpha $}-Fe$_{2}$O$_{3}$ has been considered as a potential photoelectrocatalyst for solar driven photoelectrochemical (PEC) water splitting to make hydrogen. However, as \textit{$\alpha $}-Fe$_{2}$O$_{3}$ is a charge-transfer type insulator, the poor conduction properties have limited its efficiency as a PEC material. We will present our study on the doping of group IIIA elements in \textit{$\alpha $}-Fe$_{2}$O$_{3}$ to improve its performance. All the calculations were done with DFT+$U$. The main electronic features of \textit{$\alpha $}-Fe$_{2}$O$_{3}$ remained almost unchanged for group IIIA doping. While for Al-doping, the band gap remained almost the same, for Ga and In substitution the band gap marginally increased. However, increased conduction and PEC efficiency has been experimentally reported for Al-doped \textit{$\alpha $}-Fe$_{2}$O$_{3}$. It will be shown that the change in volume plays an important role in this behavior. A dramatic increase in photo-response cannot be expected for this type of doping in \textit{$\alpha $}-Fe$_{2}$O$_{3}$.