catalyst hydrogen storage media d ~ nm Pt nanoparticles Pt NPs electrodes for fuel cells molecular size chemisorbed molecules 195 Pt NMR of Pt NPs depends on Electron states of Pt atoms on the surface of Pt NPs are remarkable ! Point-by-point plots of the peak area of the spin echoes on variable-field Solid-state 195 Pt NMR commercial Pt NPs B 0 / 0 kG/MHz) a few MHz The spins excited by conventional /2 pulses a few hundred kHz, at most Peak positions of Pt compounds B 0 / 0 kG/MHz) [PtF 6 ] 2- bulk Pt H 2 PtCl 6 H 2 PtI 6 (standard) chemical shift Knight shift Pt complex Instruments in Kyoto University) variable-field cryogen-free magnet OPENCORE NMR spectrometer[2][3] a home-built probe amplifier PC controller K1K1 K0K0 K2K2 K bulk B 0 / 0 kG/MHz) 195 Pt NMR of Pt NPs cubo-octahedral Pt NPs sub-subsurface n = 2 surface (n = 0) subsurface (n = 1) 195 Pt NMR of Pt NPs bulk Pt (n = ) K bulk : the Knight shift on bulk Pt metal K 0 : the Knight shift on the surface Pt atoms K n : the Knight shift on the nth Pt layer n: layer number m: healing factor The NMR layer model for Pt NPs healing length m0.23 nm phenomenological NMR layer model[4][5] bulk moiety n0.23 nm the thickness of each Pt layer 0.23 nm core polarization by 5d conduction electron surface the additional effect of hybridization of 5d and 6s band electron configuration of Pt atom: 6s 2 5d 8 high 5d electron DOS at Fermi energy low 5d electron DOS at Fermi energy 195 Pt NMR of Pt NPs protected by n-alkylthiols (1) B 0 / 0 kG/MHz) C6 C10 all d 2-3 nm Pt complex ? Pt-complex (H 2 Pt(OH) 6 ) ? surface B 0 / 0 kG/MHz) C12 Pt-complex ? B 0 / 0 kG/MHz) Pt NMR of Pt NPs protected by n-alkylthiols (2) Pt complex ? C18 B 0 / 0 kG/MHz) surface