Role of the Controlled Periodic Illumination (CPI) for Enhancing the Photonic Efficiency of a Photocatalytic System

Photonic efficiency measurements of the photoeffects at semiconductor surfaces for pollutant abatement and value-added product generation (e.g. H2 in the hydrogen evolution reaction, HER)are usually carried out under continuous irradiation of the catalyst. In the last decades Controlled Periodic Illumination (CPI) was proposed as a way to increase the photonic efficiency of irradiated semiconductor systems.. CPI consists in the modulation of the incident radiant power, alternating light and dark periods with given duty cycle, intensity and frequency. The rationale underlying the use of CPI to enhance photonic efficiency is the exploitation of dark periods to allow slow reactions proceed, to induce new reactions or to free up space on the surface of the catalyst. In this short review, we will highlight the strengths and weaknesses of some of the works published so far on the abatement of pollutants and the production of hydrogen using CPI.