H2 Production during Zn/ZnO nanoparticle synthesis
The tow-step water-splitting thermochemical cycle of Zn/ZnO redox reactions consisting of a first endothermic step based on solar high temperature dissociation of the oxide and a second endothermic hydrolysis step synthesizing H2 and ZnO can be used for production of H2 from renewable energy sources (solar).
A novel process for this second step encompasses formation of Zn nanoparticles by steam-quenching a Zn(g) flow followed by in situ hydrolysis. The process is experimentally demonstrated at the laboratory scale using a tubular aerosol flow reactor featuring a Zn-evaporation, a mixing and a reaction zone. In the reaction zone, operated at and just below the Zn(g) saturation temperature, Zn particles with an average crystallite size of 69 nm were formed and hydrolyzed with chemical conversion of up to 70%. The onset of H2 formation is traced to ZnO formation by surface growth along the reactor axis using X-ray diffraction and microscopic analyses of Zn and ZnO particles collected on the reactor walls and effluents.
Recent, relevant references:
- Wegner, K., H. C. Ly, R. J. Weiss, S. E. Pratsinis, and A. Steinfeld, “In situ formation and hydrolysis of Zn nanoparticles for H2 production by the 2-step ZnO/Zn water-splitting thermochemical cycle,” Int. J. Hydrogen Energ., 31 (1), 55-61 (2006).
- Weiss, R. J., H. C. Ly, K. Wegner, S. E. Pratsinis, and A. Steinfeld, “H2 Production by Zn Hydrolysis in a Hot-Wall Aerosol Reactor,” AIChE J., 51 (7), 1966-1970 (2005).