A profound understanding of the band-edge electronic structure is crucial for advancing the development of highly efficient photocatalytic materials and unraveling the underlying mechanisms. This study employs a unified and consistent assessment protocol, offering a systematic exploration of the inherent connections between the band-edge electronic structure and the photo(electro)catalytic performance of a series of delafossite ABO2 compounds (A = Cu, Ag; B = Al, Ga, In). These compounds exhibit characteristics of indirect bandgap semiconductors, with fundamental and optical bandgaps spanning from 1.45 to 3.57 eV. Notably, the Cu-based ABO2 compounds display a significantly larger fundamental bandgap and excel as photocathode materials when the B-site element is held constant. Among these, CuInO2 emerges as the most promising candidate, showcasing superior photo(electro)catalytic performance. Extensive density functional theory calculations unravel intricate insights into the interplay between the band-edge electronic structure and valence orbital hybridization of the A- and B-site elements, providing invaluable perspectives for comprehending and enhancing the photo(electro)catalytic performance of such compounds. The findings in this study not only establish robust theoretical foundations for integrating ABO2 compounds into the field of photo(electro)catalysis but also lay the groundwork for future material design and optimization.
Cr4+-activated phosphors are important candidate materials for NIR-II light sources, but providing a suitable lattice coordination environment for Cr4+ and achieving long wavelength broadband emission remains a challenge. In this work, a series of Cr4+-activated ABO2 (A = Li, Na; B = Al, Ga) phosphors were successfully prepared. Due to the presence of only tetrahedral coordination structures available for Cr4+ to occupy in the matrix crystal ABO2, the valence state and luminescence stability of Cr4+ are effectively guaranteed. Through the cation substitution design of A-site (Na → Li) and B-site (Ga → Al), the [BO4] tetrahedron is distorted and expanded, which degrades the symmetry of the Cr4+ coordination crystal field. Consequently, the central wavelength of the Cr4+ emission peak is tuned from 1280 to 1430 nm, and the fwhm is significantly extended from 257 to 355 nm. Thebroadband NIR-II light sources constructed with LiAlO2: 0.03Cr4+ and NaGaO2: 0.03Cr4+ phosphors verify their important potential applications in nondestructive testing and biological imaging.
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