In photocatalysis experiments, is the quantum yield you calculate really the AQY (Absolute Quantum Yield)?

There are times when you might find yourself in a situation where you need to calculate quantum yields for photocatalysis experiments. After consulting the literature, you come across various terms like "quantum yield QY," "quantum efficiency QE," "apparent quantum yield AQY," and "apparent quantum efficiency AQE."

This leads to a series of questions: What do these quantum yield terms mean? Which quantum yield should you use to address your research questions? How are these quantum yield values calculated?

Let's take a systematic look at the calculation methods and distinctions for quantum yields, quantum efficiencies, apparent quantum yields AQY, and STH in photocatalysis experiments.

Is the quantum yield (QY) you calculate in photocatalysis experiments really the Absolute Quantum Yield (AQY)?

Quantum Yields and Quantum Efficiencies in Photochemistry

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

qp: Photon flux;

Photon flux qp^[2]: The number of photons radiated by the light source per unit time interval. It's a function of wavelength λ.

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

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

: Incident photon flux.

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

Is the quantum yield (QY) you calculate in photocatalysis experiments really the Absolute Quantum Yield (AQY)?

Photon efficiency and photon yield emphasize the concept of "number of incident photons in the reaction system," which can be directly calculated. Moreover, photon yield and photon efficiency particularly emphasize the "measurement within a specified time interval (typically initial conditions)." 

From the definitions and formulas of quantum efficiency and photon efficiency, it can be seen that "efficiency" emphasizes incident light within a specific wavelength range, which is a continuous spectrum. During the calculation, integration over wavelength λ is required.

From the definitions and formulas of quantum yield and photon yield, "yield" emphasizes monochromatic light as the incident light.

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

Ne: Total number of transferred electrons;

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 view the "Quantum Yield (AQY) Calculation Guide," you deserve to have it!

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

The above content describes the parameters related to the photo-electrochemical energy conversion efficiency in photocatalysis. If you want to learn more about quantum yields in photoelectrochemical experiments, please click on the article "Quantum Yields and Quantum Efficiencies in Photoelectrochemical Catalysis Experiments."

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