The effectiveness of Cs-exchanged phosphotungstic acid as a recoverable solid acid additive for the direct synthesis of hydrogen peroxide (H2O2) using an Au Pd/TiO2 catalyst is investigated and compared to the promotion effect of common oxides and nonhalo acids. A clear improvement in catalytic activity toward H2O2 synthesis is reported when utilizing Cs containing heteropolyacids in addition to a standard H2O2 synthesizing catalyst. The effect of Cs content on the promotion of H2O2 formation is investigated, and the feasibility of a reusable heterogeneous additive has been explored revealing that the presence of the acid additive not only stabilizes the H2O2 that is produced but also increases the H2O2 synthesis rate.