Anomalous Photocatalytic Activity of Nanocrystalline γ-Phase Ga<sub>2</sub>O<sub>3</sub> Enabled by Long-Lived Defect Trap States
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Bibliographic record
Abstract
Semiconductor photocatalysis has emerged as an efficient and sustainable advanced oxidation process for wastewater treatment and other environmental remediation and forms the basis for water splitting and solar-to-fuel conversion. Nanocrystalline metal oxides are particularly promising photocatalysts because of their efficiency, stability, and low toxicity. However, the influence of the crystal structure and defects on the photocatalytic activity of these polymorphic materials is still poorly understood. In this work we investigated the structural dependence of the photocatalytic activity of nanocrystalline Ga 2 O 3 . We demonstrate that metastable cubic-phase γ-Ga 2 O 3 prepared from colloidal nanocrystals exhibits an anomalously high photocatalytic activity, which rapidly decreases upon thermally induced transformation to monoclinic β-Ga 2 O 3 . Using steady-state and time-resolved photoluminescence measurements we showed that the reduction in photocatalytic activity upon annealing is accompanied by a decrease in native defect (i.e., oxygen vacancy) concentration and interactions. Trapping charge carriers in defect-induced states in γ-Ga 2 O 3 nanocrystals results in a reduced rate of charge recombination and enhanced interfacial charge transfer, which has been unambiguously confirmed by comparative measurements using In 3+ -doped Ga 2 O 3 . These phenomena are enabled by the unique character of defect states in γ-Ga 2 O 3 nanocrystals which have much longer lifetime than typical metal oxide surface states. Using various scavengers, we demonstrated that reactive radicals (OH • and O 2 •– ) formed by photogenerated charge carriers play a key role in the mechanism of photocatalytic degradation by Ga 2 O 3 . The results of this work demonstrate how manipulation of the location and electronic structure of defect sites in nanostructured metal oxides can be effectively used to control charge carrier separation and enhance photocatalytic activity, without a detriment to high surface-to-volume ratio.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it