A photocatalyst molecule absorbs a photon (falling dot) and jumps to an
excited state that is both a stronger oxidant and reductant than its ground
state. In that brief window it transfers a single electron to a nearby
substrate, converting it (turns orange) while relaxing back to the ground
state β ready to absorb another photon and repeat the cycle.
PC + hΞ½ β PC*
PC* + Substrate β PCβΊ/β» + Substrateβ’
PCβΊ/β» + co-reductant β PC (cycle closes)
rate β Ξ¦_light Γ [PC] Γ (1 β e^(βΡ·[PC]Β·l))
- Light intensity β photon flux hitting the reactor from the lamp bar above.
- Catalyst loading β concentration of yellow photocatalyst dots.
- Substrate reactivity β how readily an excited catalyst hands off its electron before decaying uselessly.
- Wavelength β must match the catalyst's absorption band; off-band light wastes photons.