Improved photocatalytic activity of α-Fe2O3 by introducing B, Y, and Nb dopants for solar-driven water splitting: a first-principles study

Abstract

Advanced theoretical investigations are crucial for understanding the structural growth mechanisms, optoelectronic properties, and photocatalytic activity of photoelectrodes for efficient photoelectrochemical water splitting. In this work, we conducted first-principles calculations aimed at designing α-Fe₂O₃ photoelectrodes incorporating mono-dopants such as boron (B), yttrium (Y), and niobium (Nb), as well as co-dopants (B, Y) and (B, Nb) to enhance the photocatalytic activities of photoelectrochemical cells (PECs). We assessed the thermodynamic phase stability by calculating formation enthalpy (E_f) and examining material properties, including microstrain (μ_ε) and crystallite size (D). The mono-dopants, Y and Nb, and the co-dopants, (B, Y) and (B, Nb), exhibited negative E_f values under the substitutional doping method, confirming their thermodynamic phase stability and suggesting their practical viability for experimental implementation. Notably, the values of μ_ε and D fell within the ranges observed experimentally for α-Fe₂O₃, indicating their effectiveness in growth mechanisms. To gain a comprehensive understanding of the optoelectronic properties of doped α-Fe₂O₃, we calculated the electronic band structure, density of states, atom's ionic charge, and optical absorption coefficient (α). This analysis allowed us to examine the improvements in the electronic charge characteristics and photon–electron interactions. B doped α-Fe₂O₃ led to the formation of impurity bands, which were effectively mitigated by utilizing co-dopants (B, Y) and (B, Nb). The metal dopants, Y and Nb, significantly increased the charge carrier density, while the co-dopants, (B, Y) and (B, Nb), substantially enhanced light absorption in the visible spectrum. These improvements in the electronic and optical properties of α-Fe₂O₃ indicate its potential for application in photocatalytic water splitting.