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Anodic H2O2 Production via CO3 2-/HCO3 --Mediated Spillover Effect in Three-Phase Electrochemical System
Mengdi Sun1, Jiating Chen1, Yang Peng1
1School of Environmental Science and Engineering, Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou, China.
Abstract:
Two-electron water oxidation reaction (2e- WOR) mediated by (bi)carbonate (CO3 2-/HCO3 -) is promising for anodic H2O2 production. However, previous H2O2 yields are usually unsatisfactory due to low local CO3 2-/HCO3 - concentration at the solid/liquid interface. These sluggish reaction rates mainly result from the restricted ion diffusion, and the obstacle of by-product O2 bubbles. To resolve this puzzle, a three-phase WOR system based on CO2 (g)/dual-catalyst composite (s)/KOH (l) is adopted. At the three-phase interface, a high local concentration of CO3 2-/HCO3 - can form in the CO2 adsorption unit and transfer to the WOR catalyst unit via the CO3 2-/HCO3 --mediated spillover effect. As a result, the largest H2O2 yield of 51.62 mM at 50 mA cm-2 was realized, superior to that of the conventional two-phase system. Density functional theory (DFT) calculations, electrochemical and CO2 adsorption tests, and in situ Fourier transform infrared spectra (FTIR) results jointly confirmed the larger adsorption amount of CO3 2-/HCO3 - ions, the spillover of CO3 2-/HCO3 - and their transformation to HCO4 -, and the whole reaction processes from CO2 adsorption to final H2O2 production at the three-phase interface. This is the first application of the three-phase design in WOR, which can provide guidance for efficient H2O2 synthesis in 2e- WORs and can also be applied in other electrochemical WORs.
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