An LED photoreactor is a device that utilizes light-emitting diodes (LEDs) as the light source and combines it with chemical reactor design to achieve processes such as photocatalysis, photosynthesis, or photodegradation. Its working principle is based on the interaction between light and matter, optimizing the efficiency of the target reaction by precisely controlling light parameters (wavelength, intensity, irradiation mode, etc.) and reaction conditions (temperature, pressure, concentration, etc.). Here is a detailed analysis of its core working principles:

1. Characteristics of LED Light Sources

• Monochromaticity: LEDs can emit light of specific wavelengths (such as ultraviolet, visible, or near-infrared), matching the absorption spectrum of the reactants and reducing energy waste.

• High Efficiency and Energy Saving: Compared with traditional light sources (such as mercury lamps and xenon lamps), LEDs have high electro-optical conversion efficiency, generate less heat, and have a long lifespan (up to tens of thousands of hours).

• Fast Response: They can be instantly turned on or off or have their brightness adjusted, enabling pulsed or dynamic light control to meet different reaction requirements.

• Compact Design: LEDs are small in size and easy to integrate into the reactor, achieving a high light intensity density distribution.

2. Core Components of the Photoreactor

• LED Array: Arranged according to reaction requirements (such as planar, circular, or point light sources) to provide uniform or gradient illumination.

• Reaction Chamber: Made of transparent materials (such as quartz or glass) to allow light penetration and accommodate the reactants.

• Photocatalyst Carrier (Optional): For example, a titanium dioxide (TiO₂) coating is used for photocatalytic reactions (such as the decomposition of organic substances).

• Temperature Control System: Maintains a stable reaction temperature through cooling water or semiconductor cooling chips (to prevent overheating of the LEDs or uncontrolled reaction heat).

• Stirring/Flow System: Ensures uniform mixing of the reactants and improves light contact efficiency.

3. Working Principle Process

(1) Light Absorption and Excitation

• Light Matching: The photon energy (E = hν = λhc) emitted by the LEDs needs to match the bandgap of the reactants or catalysts to trigger electron transitions.
  For example, the TiO₂ photocatalyst absorbs ultraviolet light (λ < 388 nm) to generate electron-hole pairs.

• Direct Excitation: Light energy directly drives the absorption of photons by reactant molecules (such as photolytic water splitting to produce hydrogen) or sensitizers (such as dye molecules).

(2) Occurrence of Photochemical Reactions

• Photocatalytic Reactions:
  After the separation of electron-hole pairs, they participate in reduction (such as the reduction of H⁺ to H₂) and oxidation (such as the oxidation of organic substances to CO₂) reactions, respectively.
  Example: TiO₂ photocatalytically degrades formaldehyde (HCHO → CO₂ + H₂O).

• Photosynthetic Reactions:
  Simulating natural photosynthesis, light energy is used to fix CO₂ and generate organic substances (such as artificial chloroplast systems).

• Photodegradation Reactions:
  High-energy photons directly destroy the molecular structure of pollutants (such as ultraviolet light degrading pesticide residues).