Adsorption of Aspartic Acid on Ni{100}: A Combined Experimental and Theoretical Study

Understanding the interaction of amino acids with metal surfaces is essential for the rational design of chiral modifiers able to confer enantioselectivity to metal catalysts. Here, we present an investigation of the adsorption of aspartic acid (Asp) on the Ni{100} surface, using a combination of synchrotron X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure, and density functional theory simulations. Based on the combined analysis of the experimental and simulated data, we can identify the dominant mode of adsorption as a pentadentate configuration with three O atoms at the bridge sites of the surfaces, and the remaining oxygen atom and the amino nitrogen are located on atop sites. From temperature-programmed XPS measurements, it was found that Asp starts decomposing above 400 K, which is significantly higher than typical decomposition temperatures of smaller organic molecules on Ni surfaces. Our results offer valuable insights into understanding the role of Asp as a chiral modifier of nickel catalyst surfaces in enantioselective hydrogenation reactions.