3D Metal-Oxide Nanoparticle Photocatalysis: Surface Redox Reactor

Light Source

Wavelength λ 350 nm

Photon energy 3.54 eV

Photon flux 70%

Pollutant molecules 22

Live Readouts

Band gap

3.20 eV

Cutoff λ

387 nm

e⁻/h⁺ pairs

Recombined

•OH generated

Quantum yield

Pollutant left

Mineralized

How it works

This is the same photocatalytic redox chemistry as the 2D band-diagram version, viewed spatially instead: photons of a chosen wavelength arrive at the TiO₂ nanoparticle from random directions in 3D, and only those at or above the 3.2 eV band gap (λ ≤ 387 nm) are absorbed. Each absorption nucleates an electron and a hole inside the crystal that random-walk in three dimensions toward the surface — first to arrive there reacts; if they collide with each other first, they recombine and are lost as heat, capping the real quantum yield.

E_photon = 1240 / λ(nm)  eV
absorbed ⇔ E_photon ≥ 3.20 eV
h⁺(surface) + OH⁻ → •OH
e⁻(surface) + O₂  → O₂•⁻
•OH + pollutant → CO₂ + H₂O

Wavelength — crossing 387 nm shuts the whole reaction off; watch the photon streaks stop nucleating carriers.
Photon flux — how many photons per second are fired at the particle.
Pollutant molecules — orbit the reactor in the surrounding solution shell; a hydroxyl radical that reaches one mineralizes it into CO₂ + H₂O fragments that drift away.
Quantum yield — fraction of absorbed photons whose hole actually produced a radical rather than being lost to recombination, exactly the efficiency metric used to rate real photocatalysts.

Drag to orbit the reactor; scroll to zoom.

TiO₂ nanoparticle electron e⁻ hole h⁺ •OH radical pollutant

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