Effects of additives on H(2)o(2) formation rate and yield were studied to prevent H(2)o(2) decomposition and it was found that high yield and the formation rate of H2O2 can be obtained by using NaBr-H3PO4 additives in spite of much smaller amount compared to NaCl-H2SO4 system,. Since Br-adsorbed strongly on Pd-Au nano colloid surface, relatively high formation rate of H2O2 was attained at 298 K. Therefore, from industrial point of view, addition of NaBr (2 mM) and H3PO4 (0.5 mM) to reaction media for H2O2 direct synthesis, was highly beneficial. However, the H2O2 accumulation experiment, it was found that the H2O2 became negligibly small after 20 h and the decomposition of formed H2O2 became dominant reaction after 40 h. Deactivation of catalyst seems to be related with the decrease in Br- concentration, surface segregation of Pd and particle size growth. After 25 h, H2O2 concentration was reached a value of 5.8 wt% at 298K. (C) 2014 Elsevier B.V. All rights reserved.