Hydrogen Production from Formaldehyde at Different pH Values by Popcorn-like Cu Microcrystals

Photocatalytic reforming of formaldehyde for hydrogen production over popcorn-like Cu microcrystals have been investigated and compared under different reaction conditions. In this work, we find that popcorn-like Cu microcrystals can catalyze hydrogen production from formaldehyde solution at various pH values rather than only in alkaline conditions as previously reported in the literature. Furthermore, the visible light irradiation efficiently enhances the hydrogen generation rate. A new plasmonic catalytic mechanism is proposed on the basis of the facts that the popcorn-like Cu microcrystals are photoexcited by the visible light due to plasmon resonance and the unpaired electrons immigrate to the surface of formaldehyde to induce the redox reaction. The alkaline condition is determined to be the appropriate condition for the reaction and the popcorn-like Cu microcrystals are very stable during the catalysis process. This study may provide a new insight that the reforming reaction of formaldehyde for hydrogen production not only occurs in alkaline solutions, but also in neutral and acidic conditions, with light irradiation further improving the efficiency.