Related Experiment Video
Updated: May 17, 2026
10:21
Developing Photosensitizer-Cobaloxime Hybrids for Solar-Driven H2 Production in Aqueous Aerobic Conditions
Published on: October 5, 2019
Titania-based true heterogeneous photocatalysis
1IRCELYON (Institute of Research on Catalysis and Environment of Lyon); UMR n 5256, CNRS, Université Lyon1, 2 Avenue Albert Einstein, 69 626, Villeurbanne cedex, France. jean-marie.herrmann@ircelyon.univ-lyon1.fr
Environmental Science and Pollution Research International
|October 12, 2012
Summary
Heterogeneous photocatalysis is a subset of heterogeneous catalysis. True catalytic reactions require high turnover numbers (TON) and quantum yields (QY) for efficient pollutant degradation and air purification.
Area of Science:
- Chemistry
- Materials Science
- Environmental Science
Background:
- Heterogeneous photocatalysis historically originates from heterogeneous catalysis.
- True (photo-)catalytic reactions require specific criteria for accurate assessment.
- Photocatalytic activity is influenced by five key physical parameters: catalyst mass, wavelength, reactant concentrations, temperature, and radiant flux.
Purpose of the Study:
- To establish criteria for identifying true heterogeneous photocatalytic reactions.
- To define key performance metrics for photocatalytic processes.
- To provide recommendations for conducting reliable photocatalysis studies.
Main Methods:
- Recalling historical context and defining criteria for photocatalysis.
- Analyzing the influence of physical parameters on reaction rates.
- Characterizing reactions using quantum yield (QY), turnover number (TON), and turnover frequency (TOF).
Main Results:
- Photocatalytic activity is governed by catalyst mass, wavelength, reactant concentrations, temperature, and radiant flux.
- True catalytic reactions exhibit a turnover number (TON) significantly greater than 1 (orders of magnitude).
- Radicals are identified as primary reaction intermediates.
Conclusions:
- Rigorous characterization using QY, TON, and TOF is essential for true photocatalysis.
- A high TON is a definitive indicator of genuine catalytic behavior.
- Recommendations are provided for performing reliable photocatalytic reactions, including mass balance determination.
Related Concept Videos
01:22Heterogeneous Catalysis
Heterogeneous catalysis involves a catalyst in a different phase from the reactants. It is a process where the catalyst and the reactants are in distinct phases, typically solid and gas or liquid.Most heterogeneous catalysts are metals, metal oxides, or acids. The list includes transition metals like iron (Fe), cobalt (Co), nickel (Ni), palladium (Pd), platinum (Pt), chromium (Cr), manganese (Mn), tungsten (W), silver (Ag), and copper (Cu). These metals possess partially vacant d orbitals that...
02:50Catalysis
The presence of a catalyst affects the rate of a chemical reaction. A catalyst is a substance that can increase the reaction rate without being consumed during the process. A basic comprehension of a catalysts’ role during chemical reactions can be understood from the concept of reaction mechanisms and energy diagrams.
01:27Catalysis
Catalysis influences the rate of chemical reactions by providing an alternative reaction pathway with lower activation energy. A catalyst speeds up a reaction, but it is not consumed during the process. The fundamental principle of catalysis is the ability of a catalyst to alter the reaction mechanism, often introducing a more efficient pathway than the uncatalyzed process.In a catalyzed reaction, the catalyst participates directly in the reaction mechanism. It interacts with reactants to form...
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.