In this work, platinum-palladium alloy nanoparticles/large mesoporous carbon nanocomposites (Pt(x)Pd(y)/LMC) (X:Y indicates the different Pt, Pd atomic ratios) are prepared. Transmission electron microscopy, nitrogen adsorption-desorption, X-ray photoelectron spectra and X-ray diffraction were used to characterize the morphology and structure of LMC or its nanocomposites. Hydrogen peroxide and nitrite were employed as the probes to measure the electrochemical applications of Pt(x)Pd(y)/LMC. The introduction of Pt(x)Pd(y) alloy nanoparticles on LMC matrix facilitates hydrogen peroxide reduction and nitrite oxidation compared to Pt deposited on LMC matrix (Pt/LMC) and LMC. Amperometry was selected to evaluate the electrocatalytic activity of the Pt(1)Pd(1)/LMC nanocomposite modified glassy carbon electrode (Pt(1)Pd(1)/LMC/CCE). Results indicate that the Pt(1)Pd(1)/LMC/GCE shows higher electrocatalytic performance (wider linear range, lower detection limit and higher sensitivity) for hydrogen peroxide reduction and nitrite oxidation than many sensors reported before. The easy fabrication and excellent electrocatalytic capability of the Pt(1)Pd(1)/LMC/GCE can be expected to find practical applications to detect other compounds. (C) 2011 Elsevier B.V. All rights reserved.