Highly Efficient H₂O₂ Electrogeneration Enabled by Controlling the Wettability of Gas Diffusion Electrodes and the Reaction Pathway in Divided Cells

Abstract

Efficient electrochemical synthesis of H 2 O 2 via a two-electron oxygen reduction reaction (2e − -ORR) has been intensively pursued in the past few years, yet its potential application is still challenging due to the slow transportation of gaseous reactants and numerous competitive reactions in the electrolytic cell. Herein, we report that efficient electrochemical production of H 2 O 2 can be achieved via tuning the wettability of the gas diffusion electrode (GDE) to the Wenzel−Cassie coexistence state (WCS) and controlling the electrochemical reaction pathway using a proton exchange membrane (PEM) divided cell. By tuning the wettability, the electrogeneration of H 2 O 2 reached to 1326 mM with 59% current efficiency after 120 min. It is revealed that the reaction pathway for 2e − -ORR can be controlled by manipulating the crossover or diffusion of the ions or intermediate reactants via different membranes, and the electrogeneration of H 2 O 2 is about 10 times higher in the PEM-divided cell compared to that in the undivided cell. These findings highlight the importance of GDE surface wettability and the reaction pathway for electrochemical synthesis of H 2 O 2 , paving an alternative way to develop efficient electrochemical synthesis systems.

Recent Progress of Transition Metal Selenides for Electrochemical Oxygen Reduction to Hydrogen Peroxide: From Catalyst Design to Electrolyzers Application

“…alleviate or even lift the gas diffusion limitation. Wang et al [119] reported an economical commercial CB-based GDE with efficient H 2 O 2 production by tuning the wettability of the GDE. A quasicontinuous gas layer forms over the textured surface of the electrode due to the high hydrophobicity of the catalyst layer, which improves gas transmission (Figure 9a).…”

“…It turns out that when supporting on GDE (Figure 9c), Ni 3 (HITP) 2 exhibits ORR activity and H 2 O 2 electrosynthesis rates >100-fold higher and >740-fold higher, respectively, than in an H-cell. [119] Copyright 2023, American Chemical Society. b) Possible reaction process on AC@Ti-F GDE cathode for boosting H 2 O 2 .…”

Bubble Engineering on Micro-/Nanostructured Electrodes for Water Splitting

“…25,26 For instance, micro-/ nanostructured electrodes can be used in gas evolution reactions owing to the significantly depressed bubble adhesion, while superaerophilic electrodes are used for gas consumption reactions due to their ideal gas affinity, both attracting considerable interest. 4,26,27 Typically, the bubble evolution process on the electrode experiences nucleation, growth, and detachment, commonly accompanied by bubble transportation and/or coalescence. 28,29 Bubbles commonly nucleate in cavities or defects of electrodes with nanometer size (it might nucleate at the boundaries if the defect is too big) 30 and grow up by absorbing surrounding supersaturated gas molecules until the buoyancy is large enough to overcome the adhesive force to accomplish the detachment.…”

“…With the development of synthesis and manufacturing techniques in recent decades, micro-/nanostructured electrodes, with combined distinctive structures and the intrinsic materials properties, has been gaining tremendous attention. − With tunable wettability and multifunctionality, micro-/nanostructured electrodes have exhibited enormous application potential in many fields. Specifically, the concept of gas superwetting (superaerophilic/superaerophobic) electrodes based on micro-/nanostructures has been widely recognized, which triggered substantial revolutions in gas involving electrochemical reactions. , For instance, micro-/nanostructured electrodes can be used in gas evolution reactions owing to the significantly depressed bubble adhesion, while superaerophilic electrodes are used for gas consumption reactions due to their ideal gas affinity, both attracting considerable interest. ,, Typically, the bubble evolution process on the electrode experiences nucleation, growth, and detachment, commonly accompanied by bubble transportation and/or coalescence. , …”

Ultraefficient Heterogeneous Electro–Fenton Process Integrated a Natural Dual-Interface Air-Diffusion Cathode for Water Decontamination

“…However, the traditional gas diffusion cathodes (GDE) still need O 2 /air supplement with additional aeration to generate H 2 O 2 , which increases the auxiliary energy input (∼15.6 g kWh –1 , ∼10 times of electrical synthesis energy) . The three interfaces (liquid–gas–solid, Wenzel–Cassie coexistence state) of natural air-diffusion structures (NAD) could provide high oxygen content (∼284 mg L –1 ) and diffusion property (diffusion coefficient: 2.0 × 10 –1 cm 2 s –1 ) in the air, which are designed to obtain excellent faradic efficiency for H 2 O 2 production. − Based on various porous carbon materials (i.e., carbon felt, carbon cloth, and carbon paper), the above-mentioned operation mode can significantly reduce electrical energy without an aeration device. Therefore, a highly efficient heterogeneous EF process should integrate the natural air-diffusion cathode for deep investigation.…”