Strain-Driven Phase Transitions in Delafossite Cu 1- x A x AlO 2 : A Key to Enhanced Photo(electro)catalytic Performance

• Published in: ACS applied materials & interfaces Vol. 16; no. 36; pp. 47486 - 47503
• Main Authors: Chen, Xian-Lan, Fu, Shi-Wei, Zhang, Hao, Yang, Jian, Xiang, Xianglin, Zhao, Zong-Yan
• Format: Journal Article
• Language: English
• Published: United States 11.09.2024
• Subjects: phase transitions; solid solutions; photoelectrochemistry; delafossite; photocatalysis
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.4c07982

This study investigates the impact of intrinsic strain and phase transitions on the thermodynamic stability and electronic properties of Cu A AlO solid solutions, which are key to their photocatalytic performance. It is demonstrated that Cu A AlO with A = Ag, Au, Pt can form continuous isostructural solid solutions due to relatively small compressive strain, while a substantial increase strain restricts Cu Pd AlO to forming only limited solutions. For A = Li, Na, the formation of heterostructural solid solutions is facilitated by structural motif alterations, accommodating significant differences in ionic radii and A-O bond characteristics. Specifically, Cu Li AlO exhibits a phase transition at ≈ 0.333, whereas Cu Na AlO undergoes three distinct phase transitions. Electronic structure analysis indicates that in Cu A AlO (A = Ag, Au), d -d closed-shell interactions dominate, enabling tunable band gaps with varying solubility. Nevertheless, increased intrinsic strain in metal sublattices, as seen in A = Pd and Pt, shifts antibonding states to the Fermi level, inducing a semiconductor-to-metal transition. Experimental evidence confirms that Ag ions modulate the band gaps and carrier dynamics in Cu Ag AlO , with Cu Ag AlO exhibiting heightened photoelectrochemical activity and a 38.5-fold enhancement in H production rate over CuAlO . Additionally, the coordination environment changes between alkali metals and O, induced by phase transitions, effectively tune the band edge positions and carrier dynamics of Cu A AlO (A = Li, Na) heterostructural solid solutions. Therefore, 3R-Cu Li AlO with asymmetric nonlinear dumbbell O-Cu-O demonstrates the highest photocatalytic H production activity, 72.9 times greater than CuAlO . In contrast, α-Cu A AlO with a smaller CuO octahedral splitting energy exhibits increased band gaps, resulting in diminished photocatalytic activity. This research underscores that strain-driven phase transition provides an additional control factor and new mechanism for regulating the photo(electro)catalytic activity of Cu A AlO solid solutions.