# Photoelectrochemical Degradation of Organic Compounds Coupled with Molecular Hydrogen Generation Using Electrochromic TiONanotube Arrays.
> 電気クロミックTiO₂ナノチューブアレイを用いた有機物分解と水素生成の同時実現


## Abstract

Vertically aligned TiO₂ nanotube arrays (TNTs) fabricated by electrochemical anodization were subjected to cathodic polarization, producing blue-colored Blue-TNTs with partial surface reduction of Ti⁴⁺ to Ti³⁺. This modification substantially increased donor density and electrical conductivity by several orders of magnitude. Under photoelectrochemical (PEC) conditions with a 1.64 V bias and wavelengths above 320 nm, Blue-TNTs showed markedly superior degradation of 4-chlorophenol, humic acid, and fulvic acid compared with unmodified TNTs, while photocatalytic performance without bias was comparable between the two. Hydroxyl radical probe and scavenger experiments identified surface hydroxyl radicals as the primary oxidizing species. Concurrent H₂ generation was observed exclusively under PEC conditions, with Blue-TNTs achieving more than double the H₂ production rate of intact TNTs. This enhancement was attributed to improved electrical conductivity combined with favorable band bending in the PEC configuration.

### Mechanism

Partial reduction of Ti⁴⁺ to Ti³⁺ on Blue-TNT surfaces elevates donor density and electrical conductivity; combined with band bending under PEC bias, this synergistically enhances surface hydroxyl radical generation for organic oxidation and proton reduction for H₂ evolution.

## Bibliographic

- **Authors**: Koo MS, Cho K, Yoon J, Choi W
- **Journal**: Environ Sci Technol
- **Year**: 2017 (2017-06-06)
- **PMID**: [28445067](https://pubmed.ncbi.nlm.nih.gov/28445067/)
- **DOI**: [10.1021/acs.est.7b00774](https://doi.org/10.1021/acs.est.7b00774)
- **Study type**: other
- **Delivery route**: in vitro
- **Effect reported**: not assessed

## Delivery context

This is basic research at the cellular or molecular level. For human application, inhalation is the most promising delivery route, but inhalation carries explosion risk and concentration matters (empirical LFL of 10%; high-concentration devices are not recommended).

## Safety notes

This is basic research at the cellular or molecular level. For human application, inhalation is the most promising delivery route, but inhalation carries explosion risk and concentration matters (empirical LFL of 10%; high-concentration devices are not recommended).

See also:
- [Inhalation concentration and LFL / UFL](https://h2-papers.org/en/safety-notes/inhalation-concentration)
- [Consumer Affairs Agency accident cases](https://h2-papers.org/en/safety-notes/accident-cases)
- [Inhalation safety threshold lineage](https://h2-papers.org/en/safety-notes/lineage)

---

> **Cite as**: H2 Papers — PMID 28445067. https://h2-papers.org/en/papers/28445067
> **Source**: PubMed PMID [28445067](https://pubmed.ncbi.nlm.nih.gov/28445067/)