Ink formulation and electrolytes affect electrochemical oxygen reduction into H₂O₂: a kinetic study

Area of Science:

• Electrochemistry
• Materials Science
• Green Chemistry

Background:

• The electrocatalytic production of hydrogen peroxide (H2O2) via the 2-electron oxygen reduction reaction (2e ORR) is a promising alternative to traditional methods.
• Carbon materials are key catalysts for 2e ORR, but their performance is highly sensitive to preparation and reaction conditions.
• Understanding the influence of ink formulations and electrolytes is vital for advancing H2O2 synthesis.

Purpose of the Study:

• To investigate the impact of ink formulations, catalyst loading, and electrolytes on the efficiency and selectivity of 2e ORR for H2O2 production.
• To identify optimal conditions for carbon-based catalysts in H2O2 electrogeneration.
• To provide fundamental insights into carbon-based electrode preparation for electrochemical H2O2 synthesis.

Main Methods:

• Utilized carbon black as a model catalyst for 2e ORR studies.
• Systematically varied ink formulations (Nafion and alcohol content) and electrolyte concentrations (KOH).
• Evaluated electrochemical activity and selectivity using gas diffusion electrodes, measuring current density and electron transfer numbers.

Main Results:

• An optimal ink formulation (10 μL Nafion, 1000 μL alcohol) demonstrated superior H2O2 generation efficiency.
• Optimal H2O2 production was achieved at a catalyst loading of 0.1 mg cm-2, with a current density of 0.8 mA cm-2 and an electron transfer number of 2.
• A linear correlation between electron transfer numbers and electrolyte concentration was observed, with 0.98 mol L-1 KOH yielding ideal 2e ORR.

Conclusions:

• Ink formulation and electrolyte concentration significantly affect the performance of carbon catalysts in 2e ORR for H2O2 synthesis.
• Established optimal parameters for efficient electrochemical H2O2 generation using carbon black.
• The findings offer essential guidance for the rational design of carbon-based electrodes and optimization of electrochemical H2O2 production processes.