# Energetics and efficiency analysis of a cobaloxime-modified semiconductor under simulated air mass 1.5 illumination.
> コバロキシム修飾半導体における水素生成の熱力学的特性と変換効率の解析


## Abstract

A p-type gallium phosphide (GaP) semiconductor was functionalized with cobaloxime-class molecular catalysts through polymer grafting, and its photoelectrochemical hydrogen evolution performance was characterized under simulated AM1.5 solar illumination. At the equilibrium potential for the hydrogen half-reaction, the modified photocathode produced a current density of 0.92 mA cm⁻². The open-circuit photovoltage reached 0.72 V versus a reversible hydrogen electrode, and the fill factor was 0.33, representing a 258% improvement over polymer-only electrodes lacking cobaloxime. External quantum efficiency peaked at 67% under 310 nm illumination with a +0.17 V reverse bias. Head-space gas analysis established a Faradaic efficiency lower bound of 88%. The near-linear dependence of photocurrent on illumination intensity suggests that photocarrier transport to the semiconductor–catalyst interface is a performance-limiting factor, offering guidance for future photocatalytic system design.

### Mechanism

Cobaloxime catalysts anchored to the GaP surface accept photogenerated carriers and drive proton reduction to yield molecular hydrogen. Photocarrier transport to the semiconductor–catalyst interface is identified as the rate-limiting step governing overall performance.

## Bibliographic

- **Authors**: Krawicz A, Cedeno D, Moore GF
- **Journal**: Phys Chem Chem Phys
- **Year**: 2014 (2014-08-14)
- **PMID**: [24619031](https://pubmed.ncbi.nlm.nih.gov/24619031/)
- **DOI**: [10.1039/c4cp00495g](https://doi.org/10.1039/c4cp00495g)
- **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)

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> **Cite as**: H2 Papers — PMID 24619031. https://h2-papers.org/en/papers/24619031
> **Source**: PubMed PMID [24619031](https://pubmed.ncbi.nlm.nih.gov/24619031/)