(23c) Electrocatalytic Generation of H2O2: Carbon Based Material Synthesis and Device Design for Portable Low Cost Water Purification
Through DFT calculation, we have predicted that different types of nitrogen-doped (N-doped) carbon or carbon with defects are able to selectively catalyze a 2-electron transfer oxygen reduction. We synthesized different types of carbon based materials and tested them along with some commercially available mesoporous carbons. Our results suggest that carbon defect sites without heteroatom doping could serve as the active center. The best catalyst by far is able to catalyse the reaction with no over-potential under alkaline condition with over 90% selectivity.
In this study, prototype devices, both fuel-cell and electrolyzer setups have also been designed and tested. Early results in a fuel-cell setup shows that H2O2 has higher affinity towards the aqueous phase as compared to the gas phase. Also H2O2 can be easily decomposed in contact with transition metals cations and reductive organic compounds. Considering the fact that electrocatalytic H2O2production will have the largest impact in the developing world, itâ??s desirable to have a simple material manufacturing process and low material cost. All these considerations lead to the current electrolyzer design using plastic with no Nafion membrane and precious metal catalysts involved.
In our electrolyzer design, the produced H2O2 is up-concentrated in the electrolyte. At the current stage, the electrolyzer cell is able to operate with 50 mA overall current at pH 13 with an applied cell potential 1.7 V and faradaic efficiency close to 100%. The device can also be connected to a PV system as the energy supply. A ten-minute operation will able to accumulate 10ml solution with the concentration around 500mg/L.
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