Near Ambient Pressure XPS at Sandia (NAP-XPS)

Category: Characterization Tools

Complete understanding of hydrogenation and dehydrogenation requires knowledge of the dynamic composition and chemical state of the surface while the reactions are taking place. The surface/gas reaction rate, believed to be a rate-limiting factor for storage materials, is controlled by the chemical and physical state of the surface and near-surface regions. Traditional XPS can only be used in ultra-high vacuum conditions, allowing only ex-situ hydrogenation experiments and subsequent XPS measurements in vacuum. But the chemical reactivity and surface species can vary greatly with and without gas pressure. Near ambient pressure x-ray photoelectron spectroscopy (NAP-XPS) provides this information. In-situ studies with NAP-XPS can reveal the complex coupling between transport, surface reaction rates, and oxidation state changes when hydrogen storage materials (hydrides, sorbents) operate.1-9

System specifications:

Pressure range: UHV to 25mbar

Sample temperature: Liquid N2 to >1000 °C

Energy resolution: < 2.5 meV Kinetic energy range: 5 - 3500 eV Detector: fast delay-line detector with 190 ps time resolution. Status: To be available for use in collaboration with HyMARC in late 2017.

Near-ambient pressure XPS electron energy analyzer SPECS PHOIBOS150.

Near-ambient pressure XPS electron energy analyzer SPECS PHOIBOS150.

References

1    El Gabaly, F. et al. Measuring individual overpotentials in an operating solid-oxide electrochemical cell. Phys Chem Chem Phys 12, 12138-12145, (2010).

2    Whaley, J. A. et al. Note: Fixture for characterizing electrochemical devices in-operando in traditional vacuum systems. Rev Sci Instrum 81, (2010).

3    Zhang, C. J. et al. Measuring fundamental properties in operating solid oxide electrochemical cells by using in situ X-ray photoelectron spectroscopy. Nat Mater 9, 944-949, (2010).

4    Chueh, W. C. et al. Highly Enhanced Concentration and Stability of Reactive Ce3+ on Doped CeO2 Surface Revealed In Operando. Chem Mater 24, 1876-1882, (2012).

5    El Gabaly, F. et al. Electrochemical intermediate species and reaction pathway in H-2 oxidation on solid electrolytes. Chem Commun 48, 8338-8340, (2012).

6    Chen, Q. L. et al. Observation of Oxygen Vacancy Filling under Water Vapor in Ceramic Proton Conductors in Situ with Ambient Pressure XPS. Chem Mater 25, 4690-4696, (2013).

7    Chueh, W. C. et al. Intercalation Pathway in Many-Particle LiFePO4 Electrode Revealed by Nanoscale State-of-Charge Mapping. Nano Lett 13, 866-872, (2013).

8    Feng, Z. L. A., El Gabaly, F., Ye, X. F., Shen, Z. X. & Chueh, W. C. Fast vacancy-mediated oxygen ion incorporation across the ceria-gas electrochemical interface. Nat Commun 5, (2014).

9    Gopal, C. B., El Gabaly, F., McDaniel, A. H. & Chueh, W. C. Origin and Tunability of Unusually Large Surface Capacitance in Doped Cerium Oxide Studied by Ambient-Pressure X-Ray Photoelectron Spectroscopy. Adv Mater 28, 4692-4697, (2016).