Formation energy control of Si-doped hematite for efficient water splitting

Abstract

In this study, we report a strong correlation between the formation energy related with the crystal disorder and the water splitting performance in Si:Ti-codoped-Fe2O3. Due to the balance of the atomic radius and the Fe charge dispersion during the structural evolution process of the dual-doped hematite system, the guest Si-dopant was easily incorporated into Ti-doped hematite without destroying the symmetry of the host Ti-hematite, and thus successfully increased the charge mobility and improved the PEC performance of Si:Ti-Fe2O3. A photocurrent density of 4.5 mA cm-2 at 1.23 VRHE was achieved in the optimized Si:Ti-hematite, which is 7.5 times higher than that of the conventional hematite rod (0.6 mA cm-2 at 1.23 VRHEM), without using any expensive process or equipment, thus not compromising the cost-effectiveness of hematite. Our systematic approach made Si-doping into Ti-Fe2O3 possible by a simple and inexpensive thermal diffusion method, which may substitute for the currently representative but cost-inefficient Si-doping methods. The strategy explored in this study can be extended to other co-doping systems of metal oxide photoanodes for efficient PEC systems to achieve a substantial improvement in PEC performance.