Nitrogen-Doped Zinc Oxide for Photo-Driven Molecular Hydrogen Production

Due to its thermal stability, conductivity, high exciton binding energy and high electron mobility, zinc oxide is one of the most studied semiconductors in the field of photocatalysis. However, the wide bandgap requires the use of UV photons to harness its potential. A convenient way to appease such a limitation is the doping of the lattice with foreign atoms which, in turn, introduce localized states (defects) within the bandgap. Such localized states make the material optically active in the visible range and reduce the energy required to initiate photo-driven charge separation events. In this work, we employed a green synthetic procedure to achieve a high level of doping and have demonstrated how the thermal treatment during synthesis is crucial to select specific the microscopic (molecular) nature of the defect and, ultimately, the type of chemistry (reduction versus oxidation) that the material is able to perform. We found that low-temperature treatments produce material with higher efficiency in the water photosplitting reaction. This constitutes a further step in the establishment of N-doped ZnO as a photocatalyst for artificial photosynthesis.

Automated summary

Due to its thermal stability, conductivity, high exciton binding energy and high electron mobility, zinc oxide is one of the most studied semiconductors in the field of photocatalysis. Doping the lattice with foreign atoms can introduce defects within the bandgap, making zinc oxide optically active in the visible range and reducing the energy required for photo-driven charge separation. This study demonstrates a green synthetic procedure for achieving high-level doping and highlights the importance of thermal treatment in selecting the nature of the defect and the material's capability for specific chemistry. The low-temperature treatments were found to produce material with higher efficiency in the water photosplitting reaction.