Electrosynthesis of >20 g/L H2O2 from Air.

Huihui Li,Shasha Yang,Yang Yang,Estefanny Quispe-Cardenas,Lifeng Yin

doi:10.1021/acsestengg.1c00366

Huihui Li, Shasha Yang + Show 3 more

Open Access

https://doi.org/10.1021/acsestengg.1c00366

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Abstract

Hydrogen peroxide (HP) production via electrochemical oxygen reduction reaction (ORR-HP) is a critical reaction for energy storage and environmental remediation. The onsite production of high-concentration H2O2 using gas diffusion electrodes (GDEs) fed by air is especially attractive. However, many studies indicate that the air–GDE combination could not produce concentrated H2O2, as the [H2O2] leveled off or even decreased with the increasing reaction time. This study proves that the limiting factors are not the oxygen concentration in the air but the anodic and cathodic depletion of the as-formed H2O2. We proved that the anodic depletion could be excluded by adopting a divided electrolytic cell. Furthermore, we demonstrated that applying poly(tetrafluoroethylene) (PTFE) as an overcoating rather than a catalyst binder could effectively mitigate the cathodic decomposition pathways. Beyond that, we further developed a composite electrospun PTFE (E-PTFE)/carbon black (CB)/GDE electrode featuring the electrospun PTFE (E-PTFE) nanofibrous overcoating. The E-PTFE coating provides abundant triphase active sites and excludes the cathodic depletion reaction, enabling the production of >20 g/L H2O2 at a current efficiency of 86.6%. Finally, we demonstrated the efficacy of the ORR-HP device in lake water remediation. Cyanobacteria and microcystin-LR were readily removed along with the onsite production of H2O2.

Highlights

Hydrogen peroxide (H2O2, HP) is an important chemical in various industries, including organic synthesis, pulp or textile bleaching, wastewater treatment, energy conversion, and other applications.[1]
The annual global production of H2O2 is about 4.5 million tons in 2020 and is projected to reach 5.7 million metric tons by the year 2027.2 It is mainly produced by an anthraquinone process,[3] which consists of sequential hydrogenation, oxidation, and distillation to produce concentrated H2O2.4 This method demands significant amounts of energy and generates considerable volumes of solvent wastes.[5]
Advanced from the conventional PTFE-carbon black (CB)/gas diffusion electrodes (GDEs), this study proposed a new configuration in which PTFE should be coated on, not blended with, the CB layer

Summary

Introduction

Hydrogen peroxide (H2O2, HP) is an important chemical in various industries, including organic synthesis, pulp or textile bleaching, wastewater treatment, energy conversion, and other applications.[1]. The electrochemical reactor for ORRHP must be selective to avoid the competitive four-electron reduction reaction to produce water (eq 2)

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