Top-Down Fabricated Atomic Layer Deposited Oxides Passivated InGaN/GaN Nanostructured Photocatalysts for Artificial Photosynthesis
Bibliographic record
Abstract
Photocatalytic water splitting is regarded as a promising technology to convert solar energy into hydrogen. However, most of the photocatalysts exihibit limited efficiency because of their wide bandgap, inappropriate band edge positions for redox reactions, lower active sites, and poor charge carrier separation. In contrast to planar structures, nanowires (NWs) photocatalysts have large surface-to-volume ratios, shortened diffusion lengths, efficient charge carrier separation and transport, and enhanced optical absorption [1]. III-nitride nanostructured semiconductors, such as InGaN is a potential candidate as photocatalysts due to their bandgap engineering, suitable band edge to straddle the redox potentials. The band gap of InGaN can be controllably tuned by varying In compositions to harvest large portion of the visible solar spectrum [2]. First, we investigated photoelectrochemical (PEC) properties of planar InGaN/GaN multiple quantum wells (MQWs) with varying indium contents (~15%, ~22%, and ~27%), and identified In~22% as optimal for overall water splitting. Subsequently, we fabricated InGaN/GaN nanowires (NWs) heterostructures (In~22%) photocatalysts using a scalable silica nanosphere lithography technique. Additionally, the sidewalls of the NWs were passivated with an ultrathin layer of Al2O3 using atomic layer deposition (ALD) technique. A systematic comparison of photocurrent density with small bias potential versus reversible hydrogen electrode (VRHE) was conducted for planar, NW, and Al2O3-coated NWs of In0.22Ga0.78N/GaN heterostructures under simulated AM 1.5G solar irradiation (100 mW/cm²). The NW photoanodes showed a higher photocurrent density (1.9 mA/cm2) than their planar counterparts. On the other hand, a significant rise in photocurrent density (80%) at 1.5 VRHE was observed after deposition of a thin layer Al2O3 on NWs. More importantly, the onset potential undergoes a cathodic shift to −0.47 VRHE, indicating a reduction in the overpotential required for self-driven water splitting. Furthermore, the Al2O3-passivated NWs generated higher photvoltage (0.87 VRHE). These findings highlight the role of surface passivation in enhancing the performance of nanostructured green light-emitting In0.22Ga0.78N/GaN MQWs photoanodes for PEC applications. The study will further explore the optimal Al2O3 passivation thickness on NWs in improving PEC activity and photostability. Acknowledgement This research was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) through Alliance Grant Programs. References Dong, Wan Jae, and Zetian Mi., Journal of Materials Chemistry A11 (2023): 5427-5459. Alqahtani, Mahdi, et al., ACS Applied Energy Materials11 (2018): 6417-6424. Figure 1
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".