Enantiomeric oxidation at the surface of solid crystal surfaces is a typical homogenous reaction process. Thus, the differences in oxidation selectivity should be reflected in the adsorption energies. To answer this question, we investigated the adsorption behaviors of DOPA enantiomers at the (111) crystal surface by taking the PdGa-A crystal as a model. The three-dimensional structures of L-DOPA and D-DOPA are displayed in Fig. . Under acidic conditions, both enantiomers have a hydrophobic catechol group, a positively charged amine group, NH3 + , and a negatively charged carboxyl group, COO -. In the presence of a solid surface, the preferred adsorption sites are the highly charged cationic metals due to the cation-π interactions according to previous studies. This is further confirmed by the optimized adsorption geometry of the PdGa-A (111)-DOPA pairs using density functional theory (DFT) in this work. Both L-DOPA and D-DOPA are firmly adsorbed onto the Pd sites via the O atoms from the carboxyl group (Fig. , Fig. ). Such an adsorption geometry is consistent with the surface electronic structure of PdGa (111), where the Pd site is positively charged with higher valence states than Pd metal. The bonding lengths of Pd-O are 2.24 and 2.29 Å for L-DOPA and D-DOPA, A (111). The energy difference is 48 meV, which is higher than the thermal energy at room-temperature (~25 meV). f. Charge transfer analysis at the interface of PdGa-A/DOPA pairs. Electrons are transferred from PdGa to DOPA, which is 0.137 𝑒 -for L-DOPA and 0.006 𝑒 -for D-DOPA. respectively, which fall in the range of hydrogen bonding, but much longer than the bonds between metals and oxygen intermediates in other catalysis reactions such as oxygen evolution. To give another perspective on the bonding strength of Pd-O, the binding energies between PdGa and DOPA are calculated (Fig. ). As expected, the binding energy between the PdGa-A/L-DOPA pair is 0.063 eV, which is higher than that for the PdGa-A/L-DOPA pair (0.112 eV). The adsorption energy difference between the two DOPA enantiomers is 48 mV, which is well above thermal energy at room-temperature (~25 meV). Furthermore, we found more electrons are transferred from PdGa to L-DOPA (0.137𝑒 -) than to D-DOPA (0.006𝑒 -) (Fig. ). These quantitative calculation results undoubtedly confirmed that the adsorption of L-DOPA enantiomer is more favorable than the D-DOPA at the surface of PdGa-A crystal, which leading to the observed higher oxidation current of L-DOPA. Now we try to answer the question of why the bond formation is more favorable for L-DOPA at the PdGa-A surface. One of the promising answers is that the spin polarization of the electrons from PdGa may differ from the one from the adsorbates, which will induce differences in electron transfer efficiencies and bonding energies. With this in mind, we calculated band dispersion and extracted the spin polarization ( 𝑆𝑧 ) of the spin-angular momentum from the phase-dependent atomic-orbital projection of the Bloch wavefunction for both PdGa-A and PdGa-B (Fig. ). We found six spinspitted non-degenerate bands along the symmetry line Γ-R around the Fermi level, merging into three two-fold degenerate bands at the time-reversal invariant point Γ. Although the spin-resolved data confirm an opposite sign of 𝑆𝑧 at +𝑘 𝑦 and -𝑘 𝑦 for the sub-spin splitting bands, all components of spin polarization vanish when summed up, thus vanishing the spin angular polarization along the [111] direction. Therefore, the role of spin polarization and spin-selected electron transfers can be neglected in our case.