The adsorption of L-alanine on Ni{111} has been studied as a model of enantioselective heterogeneous catalysts. Synchrotron-based X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy were used to determine the chemical state, bond coordination, and out-of-plane orientation of the molecule on the surface. Alanine adsorbs in anionic and zwitterionic forms between 250 and ≈320 K. NEXAFS spectra exhibit a strong angular dependence of the π* resonance associated with the carboxylate group, which is compatible with two distinct orientations with respect to the surface corresponding to the bidentate and tridentate binding modes. Desorption and decomposition begin together at ≈300 K, with decomposition occurring in a multistep process up to ≈450 K. Comparison with previous studies of amino acid adsorption on metal surfaces shows that this is among the lowest decomposition temperatures found so far and lower than typical temperatures used for hydrogenation reactions where modified Ni catalysts are used. 65 With increasing coverage, alanine begins to bind as the zwitterion 66 in a bidentate mode, with surface saturation at 0.25 ML and both 67 forms of alanine coexisting on the surface. Desorption and 68 decomposition are seen to begin together at around 300 K, with 69 decomposition occurring in a multistep process below 450 K. 70 NEXAFS spectra exhibit strong angular dependence of the π* 71 resonances associated with the carboxylate group, allowing the 72 establishment of two distinct orientations with respect to the 73 surface, which are presumed to correspond to the bidentate and 74 tridentate binding modes.

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