Onion-like mesoporous carbon vesicle (MCV) with multilayer lamellar structure was synthesized by a simply aqueous emulsion co-assembly approach. Palladium (Pd) nanoparticles were deposited on the MCV matrix (Pd/MCV) by chemical reduction of H(2)PdCl(4) with NaBH(4) in aqueous media. Pd(X)/MCV (X wt.% indicates the Pd loading amount) nanocomposites with different Pd loading amount were obtained by adjusting the ratio of precursors. The particular structure of the MCV results in efficient mass transport and the onion-like layers of MCV allows for the obtainment of highly dispersed Pd nanoparticles. The introduction of Pd nanoparticles on the MCV matrix facilitates hydrazine oxidation at more negative potential and delivers higher oxidation current in comparison with MCV. A linear range from 2.0 x 10(-8) to 7.1 x 10(-5) M and a low detection limit of 14.9 nM for hydrazine are obtained at Pd(25)/MCV nanocomposite modified glassy carbon (GC) electrode. A nonenzymatic amperometric sensor for hydrogen peroxide based on the Pd(25)/MCV nanocomposite modified GC electrode is also developed. Compared with MCV modified GC electrode, the Pd(25)/MCV nanocomposite modified GC electrode displays enhanced amperometric responses towards hydrogen peroxide and gives a linear range from 1.0 x 10(-7) to 6.1 x 10(-3) M. The Pd(25)/MCV nanocomposite modified GC electrode achieves 95% of the steady-current for hydrogen peroxide within 1s. The combination of the unique properties of Pd nanoparticles and the porous mesostructure of MCV matrix guarantees the improved analytical performance for hydrazine and hydrogen peroxide.