Identification of a Fe-Dependent Optical Mode in CuAl_1–xFe_xO₂

Abstract

Delafossites are promising candidates for photocatalysis applications because of their chemical stability and absorption in the solar region of the electromagnetic spectrum. For example, CuAlO2 has good chemical stability but has a large indirect band gap, so that efforts to improve its absorption in the solar region through alloying are investigated. The effect of dilute alloying on the optical absorption of powdered CuAl1–x Fe x O2 (x = 0.0–1.0) is measured and compared to electronic band structures calculations using a generalized gradient approximation with Hubbard parameter and spin. A new absorption feature is observed at 1.8 eV for x = 0.01, which red-shifts to 1.4 eV for x = 0.10. This feature is associated with transitions from the L-point valence band maximum to the Fe-3d state that appears below the conduction band of the spin-down band structure. The feature increases the optical absorption below the band gap of pure CuAlO2, making dilute CuAl1–x Fe x O2 alloys better suited for solar photocatalysis.

Tuning electronic structure for enhanced photocatalytic performance: theoretical and experimental investigation of CuM1−xM′xO2 (M, M′ = B, Al, Ga, In) solid solutions

“…This modification optimizes the band structure and facilitates the engineering of photocatalytic performance by broadening the light absorption range and aligning the band edges with the H + reduction potential. 16,17,24 However, the existing literature on this subject has primarily focused on specific solid-solution systems or certain solubility limits, resulting in a lack of comprehensive studies on band-structure engineering for visible-light-driven photocatalysts based on delafossite solid solutions. 16,17,25 Therefore, to address this research gap and advance the field of semiconductor optoelectronic functional materials, this work aims to provide a screening method for the construction of CuM 1−x M′ x O 2 (M, M′ = B, Al, Ga, In) solid-solution photocatalysts.…”