Isolation of hydrogen from water and/or artificial seawater by sonophotocatalysis using alternating irradiation method

Sonophotocatalysis means photocatalysis with ultrasonic irradiation. Hydrogen and oxygen were obtained from water under argon atmosphere by sonophotocatalysis and each product was isolated using alternating irradiation method. This method involves irradiation in turn with ultrasound and light. Hydrogen was also isolated from sodium chloride solution, like seawater, using a similar technique. However, the ratio of products from NaCl solution was different from the ideal value. Chloride ions (Cl−) in the solution were activated to ·Cl radicals by ·OH radicals, which were produced from water by sonolysis. In other words, hydroxyl radicals (·OH) were scavenged by Cl− ions in the solution. When chloride ions (Cl−) are in the solution, it is thought that not only the amount of hydroxyl radicals (·OH) but also hydrogen peroxide decreases. Due to decreasing H2O2 and/or ·OH radicals, O2 evolution rate would be expected to decrease.