Sonochemical conversion of alcohols to hydrogen without CO₂ emission as a complementary path for solar-to-hydrogen energy conversion

Abstract Today, hydrogen attracts attention as a clean energy source that does not emit carbon dioxide during combustion. Recently, hydrogen production via sonochemical processing of a water/alcohol mixture became a hot topic as the aqueous-phase reforming approach, which is an electrically controlled process. By viewing the aqueous-phase reforming as a complementary path for solar-to-hydrogen energy conversion, this report describes an attempt to enhance the efficiency for sonochemical production of hydrogen from alcohols under a weak range of ultrasonic waves (23 and 43 kHz) at low concentration (1%–3%, w/v) of alcohols (methanol and ethanol). The rate of hydrogen production was highly elevated (over 50-fold) by replacing the air in the sonochemical chamber with nitrogen gas. In the presence of calcium carbonate, the sonochemical production of carbon dioxide from ethanol was completely blocked while hydrogen production was maintained, thus allowing a CO 2 emission-free, greener process.