Core–Shell Structured Cocatalysts for Enhancing Redox-Mediated Z-Scheme Photocatalytic Water Splitting and Producing H<sub>2</sub> and O<sub>2</sub> Separately
Bibliographic record
Abstract
The Z-scheme water splitting system with a redox couple (oxidant/reductant) that transfers electrons from an oxygen-evolving photocatalyst (OEP) to a hydrogen-evolving photocatalyst (HEP) is promising for achieving high solar-to-hydrogen conversion efficiency by harvesting a wide range of visible light and for enabling separate production of H 2 and O 2 . However, a preference for backward electron transfer often hampers the demonstration of aforementioned advantages of the Z-scheme system. Here, we show that the loading of CrO x / M cocatalysts (CrO x represents Cr 2 O 3 · n H 2 O, M = Pt, Rh, and Ni)─where nanoparticulate M metal core species are coated with a thin CrO x shell─can effectively enhance H 2 evolution on HEPs, such as SrTiO 3 and Rh-doped SrTiO 3 (SrTiO 3:Rh), with the redox couple IO 3 – /I –, by suppressing IO 3 – rereduction on the M metal surface. Electrochemical measurements using CrO x -coated and uncoated metal wires strongly support the function of CrO x shells, which are permeable to H + (or water) and H 2 molecules, but not IO 3 –, affording selective H 2 evolution on the CrO x / M cocatalysts. The impact of the CrO x shell on suppressing backward electron transfer becomes more prominent for reactions in a two-component cell with a membrane filter, wherein the accumulation of a relatively high concentration of IO 3 – is indispensable for the transfer of IO 3 – anions from the H 2 cell to the O 2 cell containing an OEP. The use of CrO x /Rh/SrTiO 3 and CrO x /Pt/SrTiO 3:Rh coupled with appropriate OEPs affords almost stoichiometric and separate production of H 2 and O 2 under UV- or visible-light irradiation, respectively, from an aqueous solution containing I – and IO 3 – . The effectiveness of the CrO x coating for enhancing H 2 evolution on the SrTiO 3:Rh HEP was confirmed for various redox species [Fe(CN) 6 ] 3–/4–, [Co(bpy) 3 ] 3+/2+, and [SiVW 11 O 40 ] 5–/6– that are operating under nearly neutral conditions, whereas CrO x dissolution under acidic conditions with Fe 3+/2+ and VO 2 + /VO 2+ redox was detrimental. The use of CrO x -based core–shell cocatalysts was proven to enhance the efficiency of visible-light-driven Z-scheme water splitting not only with IO 3 – /I – but also with other redox couples such as [SiVW 11 O 40 ] 5–/6– .
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How this classification was reachedexpand
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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".