However, the mechanism remains unclear. Both on nanoparticle catalysts and singlecrystal electrodes, cyclic voltammetry has shown that organic modification reduces the amount of OH* formed similarly to alloying. However, it is not yet clear whether this reduction in OH* is simply due to an increase in inactive sites where the surface is covered by organic molecules, preventing the adsorption of oxygen and hydroxides, or whether the organic molecules alter the properties of nearby active sites. Even if organic molecules do change the properties of surrounding active sites, the mechanism remains unknown. Sung's group argued that the adsorption of organic molecules changes the d-band structure of neighboring surface Pt atoms, destabilizing OH and enhancing activity. On the other hand, Daimon, Wada, and Hoshi proposed that the presence of organic molecules disrupts the hydrogen bond network, leading to OH destabilization. One of the reasons that eluci- Figure : Experimental and simulated volcano-plot of ORR at the electrode potential of 0.9 V vs. SHE on the Pt(111) (black), Pt(111) with melamine (red), Pt 1-x Cu x (111) (orange), other Pt alloys (purple) and transition metals (gray) calculated in this study (open dots and solid black line) and experimental data taken from previous studies (closed dots). Here, the relative change in ORR current density j compared to that on Pt(111) is plotted as a function of the redox potential of the reaction (5) relative to Pt(111), U OH -U Pt OH . Parameters k 0 2 and k 0 5 in the kinetic model were set to 0.1 and 1.0, respectively, and α 2 and α 5 were set to 1.0 following the empirical adjustment done by Rossmeisl et al. See details of the model in Methods. dating the mechanism is difficult is that the surface sites modified by organic molecules are heterogeneous, making it challenging to experimentally determine whether OH* on the active site is destabilized or not. Likewise, experimentally capturing the electronic structure of such atomically heterogeneous interfaces is not straightforward. Furthermore, the difficulty of applying FP calculations, which greatly contributed to the understanding of alloy effects, also hampers elucidation of the phenomena. On surfaces with adsorbed organic molecules, it is difficult to model interfacial water in the same way as with the ice-like bilayer model on alloys. Moreover, quasi-stable structures at 0 K using the ice-like model cannot evaluate the disruption of the hydrogen bond network, which is considered one of the effects of organic molecules. To evaluate the solvent structure, finite-temperature FP molecular dynamics (MD) would be preferable, but running the nanosecond-scale simulations required to sufficiently sample the reorientation of interfacial water demands an enormous computational cost.