Co Reconstruction by H Exposure

The interaction of hydrogen with cobalt metal is of much interest, as it frequently plays a large role in materials science, heterogeneous catalysis, electrochemistry, and energy storage. It is well understood that when a gaseous species adsorbs onto a solid surface, that surface will be altered. This alteration can be electronic, chemical, or physical, and the degree of alteration can be insignificant to substantial. In addition to hydrogen on the surface of a solid, the ability of hydrogen atoms to diffuse through surfaces makes the interaction of a solid with subsurface hydrogen of much importance. Surface as well as subsurface hydrogen can cause changes to the surface of a solid. For any given process, these changes to the surface can be beneficial or detrimental in a small or large way. Understanding the effect an adsorbate as well as subsurface species have on a surface is crucial for understanding and making improvements to important processes.

Of particular interest is the interaction of hydrogen and cobalt metal in the Fischer-Tropsch Synthesis (FTS) process. I looked to investigate the interaction between hydrogen and cobalt metal which is used as a catalyst for FTS in the form of nanoparticles. Specifically, we investigated the hydrogen and its evolution to subsurface hydrogen as atomic hydrogen has a low barrier to diffusion below the surface of transition metals. Using the STM to monitor the surface of a model polycrystalline cobalt surface, hydrogen exposures including excited atomic hydrogen were conducted. We are looking to answer questions on the effect of coverage, temperature, and species on the devleopment of hydrogen through the evolution of the cobalt surface.