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. Meanwhile, Cu/ZnO based catalysts can convert syngas (H2, CO, 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+ incorporated into one Zn vacancy. 1H MAS NMR and IR spectra demonstrate that Ga3+ cations are introduced into the Zn vacancies of ZnO lattice, which replaces H+ and thus further confirms the feasibility of our proposed model. The exchange between the H+ in Zn vacancies and D2 gas phase shows that ZnO can active H2 due to the quantized three H+ in the defect site.