Is the quantum yield you calculate in photocatalytic experiments really AQY?

I'm sure you've had moments like this - you're conducting photocatalytic experiments and need to calculate quantum yields, but when you refer to the literature, you come across various terms like 'quantum yield QY,' 'quantum efficiency QE,' 'apparent quantum yield AQY,' and 'apparent quantum efficiency AQE.'

So, the questions start piling up: What do all these quantum yields mean? Which one should I use to explain the issues in my research? How are these quantum yield values calculated?

Next, let's systematically understand the calculation methods and differences of parameters such as quantum yield, quantum efficiency, apparent quantum yield AQY, and STH mentioned in the literature.

Is the quantum yield you calculate in photocatalytic experiments really AQY?  

Quantum Yield and Quantum Efficiency in Photochemistry 

1. Quantum Efficiency (QE)^[1]: The ratio of the rate of photochemical reaction to the photon flux absorbed within a specific wavelength range. The calculation formula is as follows:

qp: Photon flux;

Photon flux qp^[2]: The number of photons radiated by a light source in a unit time interval, which is a function of wavelength λ.

2. Quantum Yield (QY)^[1]: The ratio of the number of molecules generated or consumed in the reaction system under monochromatic light excitation to the number of photons absorbed. The calculation formula is as follows:

3. Photonic Efficiency^[2]: The ratio of the measured rate of light reaction within a specified time interval (usually under initial conditions) to the photon flux of incident light within a specific wavelength range. The calculation formula is as follows:

: Incident photon flux.

4. Photonic Yield^[2]: The ratio of the measured rate of light reaction within a specified time interval (usually under initial conditions) to the photon flux of monochromatic incident light. The calculation formula is as follows:

Is the quantum yield you calculate in photocatalytic experiments really AQY?  

Both photonic efficiency and photonic yield emphasize the concept of "incident photon number in the reaction system," and they can be directly calculated. Furthermore, photonic yield and photonic efficiency especially emphasize "measuring within a specified time interval (usually under initial conditions)." 

By looking at the definitions and formulas for quantum efficiency and photonic efficiency, you can see that "efficiency" emphasizes the incident light within a specific wavelength range, which is a continuous spectrum, and in the calculation process, you need to integrate over the wavelength λ. 

By looking at the definitions and formulas for quantum yield and photonic yield, you can see that "yield" emphasizes monochromatic incident light. 

5. Apparent Quantum Yield (AQY)^[3]: The ratio of the number of electrons transferred in the reaction at a specific monochromatic wavelength to the number of incident photons.

Ne: Total number of electrons transferred; 

Np: Number of incident photons.

Number of Incident Photons N_p^[4]: The time integral of photon flux within a specified time interval Δt, dimensionless.

I: Light power density (W·m^-2);

A: Incident light area (m²); 

λ: Incident light wavelength (nm); 

t: Time (s); 

h: Planck's constant (6.62×10^-34 J·s); 

c: Speed of light (3.0×10⁸ m·s^-1).

Click to see the "Quantum Yield (AQY) Calculation Tutorial - You Deserve It!."

6. STH Energy Conversion Efficiency: The efficiency of converting input solar energy into hydrogen energy. For details, see "How to Measure 'STH Energy Conversion Efficiency' in 3 Minutes."

The above sections describe parameters related to the photo-electric energy conversion efficiency in photocatalysis. To learn more about quantum yields in photocatalytic experiments, please read the article "About Quantum Yield and Quantum Efficiency in Photocatalytic Experiments."

[1] Qureshi Muhammad, Takanabe Kazuhiro *, Insights on measuring and reporting heterogeneous photocatalysis: efficiency definitions and setup examples[J]. Chemistry of Materials, 2017, 29, 158.

[2] Braslavsky Silvia E., Braun André M., Serpone Nick*, et. al., Glossary of terms used in photocatalysis and radiation catalysis (IUPAC Recommendations 2011)[J]. Pure and Applied Chemistry, 2011, 83, 931.

 [3] Lin Huiwen, Chang Kun*, Ye Jinhua* et. al., Ultrafine nano 1T-MoS₂ monolayers with NiOx as dual co-catalysts over TiO₂ photoharvester for efficient photocatalytic hydrogen evolution[J]. Applied Catalysis B: Environmental, 2020, 279, 119387. 

[4] Zhong Tao, Yu Zebin*, Zou Binsuo*, et. al., Surface-activated Ti3C2Tx MXene cocatalyst assembled with CdZnS-formed 0D/2D CdZnS/Ti₃C₂-A40 Schottky heterojunction for enhanced photocatalytic hydrogen evolution [J]. Solar RRL, 2100863. DOI: 10.1002/solr.202100863.