PT - JOURNAL ARTICLE AU - Xia, Chuan AU - Xia, Yang AU - Zhu, Peng AU - Fan, Lei AU - Wang, Haotian TI - Direct electrosynthesis of pure aqueous H<sub>2</sub>O<sub>2</sub> solutions up to 20% by weight using a solid electrolyte AID - 10.1126/science.aay1844 DP - 2019 Oct 11 TA - Science PG - 226--231 VI - 366 IP - 6462 4099 - http://science.sciencemag.org/content/366/6462/226.short 4100 - http://science.sciencemag.org/content/366/6462/226.full SO - Science2019 Oct 11; 366 AB - Despite the widespread use of hydrogen peroxide as an oxidant and disinfectant, its commercial synthesis still requires inefficient concentration and purification steps. Xia et al. now report an electrochemical approach to synthesizing pure peroxide solutions straight from hydrogen and oxygen. Using a solid-state electrolyte, they avoid contamination of the product solution by extraneous ions. Varying the flow rate of water through the electrochemical cell tunes the final concentration over a range from 0.3% to 20% by weight.Science, this issue p. 226Hydrogen peroxide (H2O2) synthesis generally requires substantial postreaction purification. Here, we report a direct electrosynthesis strategy that delivers separate hydrogen (H2) and oxygen (O2) streams to an anode and cathode separated by a porous solid electrolyte, wherein the electrochemically generated H+ and HO2– recombine to form pure aqueous H2O2 solutions. By optimizing a functionalized carbon black catalyst for two-electron oxygen reduction, we achieved &gt;90% selectivity for pure H2O2 at current densities up to 200 milliamperes per square centimeter, which represents an H2O2 productivity of 3.4 millimoles per square centimeter per hour (3660 moles per kilogram of catalyst per hour). A wide range of concentrations of pure H2O2 solutions up to 20 weight % could be obtained by tuning the water flow rate through the solid electrolyte, and the catalyst retained activity and selectivity for 100 hours.