Selecting a light source for photocatalysis is, at its core, about letting the catalyst absorb the photons it needs. Everything else, wattage, brand, price, is secondary. A repeatable selection workflow moves from the absorption spectrum to band selection, then to intensity calibration and finally to irradiation geometry.
Measure or look up the solid-state UV-Vis diffuse reflectance spectrum of the catalyst. The absorption edge defines the shortest usable wavelength. Any photon below the band gap is wasted energy that converts to heat, shifting the reaction away from pure photocatalysis.
For broadband response, a xenon or solar-simulated spectrum works well. For a sharp absorption peak, a monochromatic LED or a xenon lamp plus band-pass filter gives higher photon efficiency. When reporting results, always state the cutoff wavelength or filter parameters, otherwise the data cannot be compared across labs.
Measure irradiance at the reaction surface with a calibrated optical power meter, and record the wavelength correction factor of the detector. Report intensity in mW/cm² together with the measurement plane. An intensity figure without position information is meaningless, because irradiance decays rapidly with distance.
Decide top, side or immersion irradiation according to the reactor, and keep the light window, liquid depth and stirrer speed consistent between runs. Geometry variations are one of the largest hidden sources of irreproducibility.
Comparing catalysts under different spectra; calibrating at the lamp port instead of the reaction plane; ignoring filter aging; and forgetting that strong UV output heats the sample and masquerades as thermal catalysis.
Perfectlight's radiation light source portfolio covers xenon, LED, mercury and laser sources with matching filters, and the light source solutions page describes typical configurations for common photocatalysis experiments.
