Sonochemical Hydrogen Production as a Potential Interference in Light-Driven Hydrogen Evolution Catalysis

The use of sonication to dissolve or disperse solids in solvents is a common practice in catalytic studies. However, the frequency and power of commercial ultrasonic baths are within the right range to trigger unwanted sonochemical reactions that can be a source of interference. Based on our own experience, we have noted that sonication used to disperse heterogeneous photocatalysts in water-alcohol mixtures as the first step in light-driven hydrogen evolution can lead to hydrogen evolution, which is not related to any photochemical or photocatalytic process. Furthermore, "dark" hydrogen evolution continues even when sonication is stopped, which can cause significant problems for time-dependent studies. To the best of our knowledge, this phenomenon has not been described as a potential issue for light-driven hydrogen evolution studies, and it should, therefore, be brought to the attention of the energy conversion research community to avoid errors in ongoing and future hydrogen evolution studies.