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Direct electrosynthesis of pure aqueous H2O2 solutions up to 20% by weight using a solid electrolyte

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Science  11 Oct 2019:
Vol. 366, Issue 6462, pp. 226-231
DOI: 10.1126/science.aay1844
  • Fig. 1 Schematic illustration of the two different H2O2 synthesis methods using H2 and O2.

    (A) Synthesis of H2O2 using diluted H2 and O2 under high pressure. Methanol used to improve the solubility of the reacting gases in the medium (44) must then be removed downstream. Other studies that avoid alcohols have been performed in acidic solutions of either HCl or H2SO4, with NaBr or NaCl as promotors (44). (B) Electrosynthesis of H2O2 using pure H2 and O2 streams separately introduced to the anode and cathode, respectively. SE represents a solid electrolyte, which consisted in this study of either functionalized styrene–divinylbenzene copolymer microspheres or inorganic CsxH3-xPW12O40 (see materials and methods). Electrochemically generated cations (H+) and anions (HO2), driven by the electric field, cross in the porous SE layer and recombine to form H2O2. DI water flowing through the porous SE layer then dissolves the H2O2 with no impurities.

  • Fig. 2 Direct electrosynthesis of pure H2O2 using H2 and O2 with porous solid electrolyte.

    (A) I-V curve of CB-10%//SE//Pt-C cell with an H+-conducting porous solid electrolyte. We define the cell voltage as negative when the cell can output energy during the production of H2O2. The positive cell voltage therefore indicates that energy input is required for the reactor. The cell voltages were iR (current × resistance)compensated (see materials and methods). (B) Corresponding FEs and production rates of H2O2 under different cell voltages. (C) Dependence of H2O2 concentration on the DI water flow rate at an overall current density of 200 mA cm−2. Up to 20 wt % pure H2O2 solutions could be continuously generated for immediate use. The data points in (A) to (C) each represent the mean of two independent measurements. (D) Removal of TOC in Houston rainwater using the H2O2 solution generated at a fixed current density of 200 mA cm−2 and a fixed DI water flow rate of 27 ml hour−1 in our 4-cm2 electrode device. A high rainwater treatment rate of 0.88 liters hour−1 (0.22 liters cm−2electrode hour−1 or 2200 liters m2electrode hour−1) was achieved to meet the drinking water standards (TOC < 2 ppm according to the Texas Commission on Environmental Quality). (E and F) Stability tests for continuous generation of pure H2O2 solutions with concentrations >1000 and 10,000 ppm, respectively. No degradation of cell voltage or H2O2 concentration was observed over the 100-hour continuous operation. The cell currents and DI flow rates were (E) 60 mA and 27 ml hour−1 and (F) 120 mA and 5.4 ml hour−1, respectively.

  • Fig. 3 Electrosynthesis of pure H2O2 solutions by 2e-ORR and water oxidation.

    (A) I-V curve for an O2//SE//H2O cell in which H2O is oxidized at the anode side to form protons and O2. A 0.5 M aqueous H2SO4 solution was used to improve ionic conductivity on the anode side and was not consumed during electrosynthesis. (B) Corresponding FEs of the O2//SE//H2O cell. (C) I-V curve and FEs for an air//SE//H2O cell generating pure H2O2 solutions. Pure H2O2 solutions were generated at a high production rate of 2.3 mmol cm−2 hour−1 (2490 mol kgcat−1 hour−1) using only air and water as cathode and anode feedstock, respectively. (D) I-V curve of the scaled-up unit cell module (80 cm2 electrode, no iR compensation), and (E) the corresponding H2O2 FEs. (F) Dependence of H2O2 concentration (up to ~20 wt %) on the DI water flow rate at a constant overall current of 8 A. The data points in (A) to (E) each represent the mean of two independent measurements.

  • Table 1 Performance metrics of different H2O2 generation methods

    PurityProductivity
    (mol kgcat−1 hour−1)
    Productivity
    (mmol cm−2 hour−1)
    Selectivity (%)StabilityMax. concentration (ppm)
    Our methodPure36603.490 ~ 95>100 hours200,000
    Direct synthesisMixture
    (8, 9, 4547)
    60.8 ~ 180N/A80.7 ~ 96Up to 4 cycles or 4 hours5300
    Electrochemical
    synthesis
    Mixture
    (4853)
    N/A0.05 ~ 1.247 ~ 93.52 ~ 6 hours3400 ~ 60,000
    Pure
    (1921)
    N/A0.16 ~ 0.28926.5 ~ 306 ~ 72 hours1400 ~ 80,000

Supplementary Materials

  • Direct electrosynthesis of pure aqueous H2O2 solutions up to 20% by weight using a solid electrolyte

    Chuan Xia, Yang Xia, Peng Zhu, Lei Fan, Haotian Wang

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods 
    • Figs. S1 to S15
    • Supplementary Text
    • Table S1
    • References 

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