Search

Polar materials, with intrinsic polarization effects, present significant potential for photo(electro)catalysis. However, the available natural polar materials in this field are quite scarce, due to the requisite structural non‐centrosymmetry. Defect engineering emerges as a promising avenue for tuning material symmetry, yet achieving the transition from centrosymmetric to non‐centrosymmetric structures and optimizing associated polarization effects remains challenging. This study demonstrates symmetry breaking in centrosymmetric 3R‐delafossite AgFeO2 through ordered oxygen defects introduction, yielding substantial macroscopic polarization. The transition is achieved via annealing post‐treatment of co‐precipitation‐hydrothermal AgFeO2 samples, with precision in oxygen defects control by tailoring annealing conditions. Experimental characterizations reveal ordered interstitial oxygen and disordered oxygen vacancies. Density functional theory calculations indicate a higher propensity for the formation of disordered oxygen vacancies compared to ordered ones, while ordered interstitial oxygen is more easily formed than its disordered counterpart. Resultant macroscopic polarization enhances photoelectrochemical performance, with photocurrent density increasing from 0.79 to 2.95 µA cm−2. Coupling macroscopic and spin polarization via external electric and magnetic fields further enhances photocurrent density (≈18.44 µA cm−2). These findings provide reference cases and strategies for applying polarization effects in photo(electro)catalytic technology. [ABSTRACT FROM AUTHOR]

Doping engineering has been recognized as an effective strategy for improving the solar‐to‐hydrogen conversion efficiency of delafossite CuFeO2‐based photocatalysts. However, a comprehensive and systematic study on the doping effect in CuFeO2 is still needed to establish a universal law. To address this, we utilized density functional theory calculations to scrutinize the doping effects of various dopants at different lattice positions. Our findings revealed that Mn replacing Fe and N replacing O are the most readily achievable doping methods under oxygen‐rich and oxygen‐poor conditions, respectively, with a maximum doping concentration of 1020 cm−3 achievable at 900 K. Interestingly, we found that doping with N for O, F for O, and Ni for Cu generates impurity levels capable of capturing photogenerated holes at the top of the valence band, while Zn for Cu and Co for Fe engender impurity levels capable of capturing photogenerated electrons at the bottom of the conduction band, thereby facilitating the separation of photogenerated electron–hole pairs. However, it is worth highlighting that Mn replacing Fe results in impurity levels forming in the middle of the bandgap, acting as a recombination center for photogenerated electron–hole pairs. Furthermore, we discovered that Mg replacing Cu or Fe serves as an example of heterovalent doping capable of promoting the solar‐to‐hydrogen conversion efficiency of CuFeO2. In isovalent doping, dopants with more valence electrons than Cu, dopants with the same valence electron as Fe, and dopants with less valence electron than O can enhance the solar‐to‐hydrogen conversion efficiency of CuFeO2. Overall, this study provides a systematic analysis of the doping effects on CuFeO2‐based photocatalysts and can be applied to doping engineering of ABO2‐type delafossite photocatalytic materials. [ABSTRACT FROM AUTHOR]

This study introduces robust screening methodology for the efficient design of delafossite CuM1−xM′xO2 solid-solution photocatalysts using band-structure engineering. The investigation not only reveals the formation rules for various CuM1−xM′xO2 solid solutions but also highlights the dependence on both lattice compatibility and thermodynamic stability. Moreover, the study uncovers the nonlinear relationship between composition and band gaps in these solid solutions, with the bowing coefficient determined by the substitution constituents. By optimizing the constituent elements of the conduction band edge and adjusting solubility, the band structure of CuM1−xM′xO2 samples can be fine-tuned to the visible light region. Among the examined photocatalysts, CuAl0.5Ga0.5O2 exhibits the highest H2 evolution rate by striking a balance between visible-light absorption and sufficient reduction potential, showing improvements of 28.8 and 6.9 times those of CuAlO2 and CuGaO2, respectively. Additionally, CuGa0.9In0.1O2 demonstrates enhanced electron migration and surpasses CuGaO2 in H2 evolution due to a reduction in the effective mass of photogenerated electrons. These findings emphasize the pivotal role of theoretical predictions in synthesizing CuM1−xM′xO2 solid solutions and underscore the importance of rational substitution constituents in optimizing light absorption, reduction potentials, and effective mass for efficient hydrogen production. [ABSTRACT FROM AUTHOR]

Employing a facile one-pot hydrothermal synthesis approach, in this work, we achieved the successful synthesis of a CuCoO2/CuO heterostructure, which was characterized by an atomic-scale intimately bonded interface. This can be utilized as a reference for the synthesis of heterostructures involving multiple compounds and their secondary phases. Notably, the CuCoO2/CuO heterostructure stands out for its superior performance in photocatalytic overall water splitting without relying on additional co-catalysts or sacrificial agents. In addition, this heterostructure displayed excellent electrocatalytic activity, photocatalytic activity for the degradation of trichloromethane, and promising PEC performance when utilized as a photocathode. A pivotal feature of the CuCoO2/CuO heterostructure is its capacity to efficiently inhibit the migration of photogenerated holes from CuCoO2 to CuO. This was attributed to the synergistic effects between the intrinsic interface electric field and pronounced valence band offset. Interestingly, this mechanism overcomes the traditional limitations associated with type-I heterostructures. Consequently, the two half-reactions of the overall water splitting process are selectively localized on opposite facets of the CuCoO2/CuO heterostructure. Overall, our findings elucidate the profound implications of band alignment in these heterostructures, offering pivotal insights for the innovation and optimization of advanced heterostructure photo(electro)catalytic materials. [ABSTRACT FROM AUTHOR]