Abstract
Titanium is an excellent getter material, catalyzes gas–solid reactions such as hydrogen absorption in lightweight metal hydrides and complex metal hydrides and has recently been shown as a potential ammonia synthesis catalyst. However, knowledge of the surface properties of this metal is limited when it absorbs large quantities of hydrogen at operation conditions. Both the conceptual description of such a surface as well as the experimental determination of surface hydrogen concentration on hydride-forming metals is challenging due to the dynamic bulk properties and the incompatibility of traditional surface science methods with the hydrogen pressure needed to form the metal hydride, respectively. In this paper, the surface pressure-composition isotherms of the titanium–hydrogen system are measured by operando reflecting electron energy loss spectroscopy (REELS). The titanium thin films were deposited on and hydrogenated through a palladium membrane, which provides an atomic hydrogen source under ultrahigh vacuum conditions. The measurements are supported by density functional theory calculations providing a complete picture of the hydrogen-deficient surface of TiH2 being the basis of its high catalytic activity.
Highlights
The widespread introduction of renewable hydrogen is still hampered by the difficulty of storing it efficiently at high volumetric and gravimetric density.[1]
The experimental setup enables the reproducible deposition of Ti onto a Pd membrane, which links the chemical potential of the thin film in ultrahigh vacuum (UHV) with the gas applied on the feed side (Figure 2).[26]
The membrane method employed in this study allows for the surface characterization of the contamination-free surfaces of highly reactive materials as titanium using surface science methods
Summary
The widespread introduction of renewable hydrogen is still hampered by the difficulty of storing it efficiently at high volumetric and gravimetric density.[1] The current technical solutions of storage as a gas under high pressure or as a liquid at very low temperatures are associated with limited storage density, efficiency, and/or safety issues.[2,3]. The catalytic conversion of H2 into energy-rich small molecules like CH4 or NH3 is a different strategy to store renewable energy. Storage is straightforward, and demand for research and development shifts to the efficient production of these fuels. TiH2 has been recognized as a potential catalyst for ammonia synthesis.[4] The subtle differences in the surface structure of the hydride compared to the metal depending on temperature and pressure have been proposed as the origin of this effect.[5]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
