Electrosynthesis of >20 g/L H₂O₂ from Air

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 H 2 O 2 using gas diffusion electrodes (GDEs) fed by air is especially attractive. However, many studies indicate that the air–GDE combination could not produce concentrated H 2 O 2 , as the [H 2 O 2 ] 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 H 2 O 2 . 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 H 2 O 2 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 H 2 O 2 .

Removal and Inactivation of Nonenveloped and Enveloped Virus Surrogates by Conventional Coagulation and Electrocoagulation Using Aluminum and Iron

“…Electrolysis during our iron electrocoagulation experiments generated 0.18 mM Fe­(II) along with 19 μM H 2 O 2 attributed to the cathodic reduction of dissolved oxygen (accompanied by dissolved oxygen depleting from 265 to 225 μM). The simultaneous presence of Fe­(II) and H 2 O 2 (and dissolved oxygen) strongly implies the initiation of electro-Fenton reactions that generate reactive oxygen species like • OH and oxoiron (IV), , which are capable of inactivating viruses. , This phenomenon can also be exploited to mitigate bacteria and oxidize recalcitrant contaminants , via iron electrocoagulation, notwithstanding electrode passivation …”

Catalysis for e-Chemistry: Need and Gaps for a Future De-Fossilized Chemical Production, with Focus on the Role of Complex (Direct) Syntheses by Electrocatalysis

“…By using a superhydrophobic natural air diffusion electrode (NADE) to improve the oxygen diffusion coefficient at the cathode as compared to the normal gas diffusion electrode (GDE) system, Zhang et al showed that it is possible to largely increase the H 2 O 2 production rate and oxygen utilization efficiency. These examples show how a deep understanding of the engineering aspects at the electrode nanoscale is a crucial factor in determining the behavior, and not only the nature, of the electrode itself . Quite similar aspects also strongly determine the behavior in NRR .…”

“…These examples show how the deep understanding of the engineering aspects at the electrode nanoscale is the crucial factor in determining the behaviour, and not only the nature, of the electrode itself. 115 Quite similar aspects are also strongly determining the behaviour in NRR. 116 Produce H2O2 rather than O2 in water splitting or other electrocatalytic reduction reactions (CO2RR and NRR) has thus the advantages of making a 2erather than a 4eprocess (with advantages in terms of rate and reduced overpotential), and obtain a higher value product.…”

Metal-Compound-Based Electrocatalysts for Hydrogen Peroxide Electrosynthesis and the Electro-Fenton Process

“…Additionally, electrode preparation methods should be carefully described, as the catalyst microstructure can affect the diffusion of O 2 and H 2 O 2 into and out of the electrode, , which can further impact the ability for H 2 O 2 to accumulate and the Faradaic efficiency. Some factors to consider include the catalyst ink compositions (solvents, ionomers, catalyst concentrations), , the properties of the electrode substrates (hydrophobicity, porosity), , and the methods of depositing the catalyst onto the electrodes (drop-casting, spray-coating, − or direct growth − ). Because many factors at the device, electrode, and catalyst levels can impact the overall electrosynthesis performance, comparing the apparent H 2 O 2 electrosynthesis performances under different cell conditions can further obfuscate atomic-level insights into the structural design of metal-compound-based 2e – ORR catalysts.…”