Hydrogen Impurities in ZnO: Shallow Donors in ZnO Semiconductors and Active Sites for Hydrogenation of Carbon Species

ZnO, as a low-cost yet significant semiconductor, has been widely used in solar energy conversion and optoelectronic devices. In addition, Cu/ZnO-based catalysts can convert syngas (H2, CO, and CO2) into methanol. However, the main concern about the intrinsic connection between the physical and chemical properties and the structure of ZnO still remains. In this work, efforts are made to decipher the physical and chemical information encoded into the structure. Through using NMR-IR techniques, we, for the first time, report a new ZnO model with three H+ cations incorporated into one Zn vacancy. 1H magic-angle spinning NMR and IR spectra demonstrate that Ga3+ cations are introduced into the Zn vacancies of the ZnO lattice, which replace the H+ cation, and thus further confirm the feasibility of our proposed model. The exchange between the H+ cation in Zn vacancies and the D2 gas phase shows that ZnO can activate H2 because of the quantized three H+ cations in the defect site.