An energy-saving pH-asymmetric electrolyzer for simultaneous methane conversion and hydrogen production

Area of Science:

• Electrochemistry
• Catalysis
• Sustainable Chemistry

Background:

• Waste acid/base neutralization energy (ENE) offers a sustainable route for chemical production and energy saving.
• Electrochemical methane oxidation (EOM) is a key process for converting methane into valuable chemicals.

Purpose of the Study:

• To develop a sustainable and energy-efficient method for electrocatalytic methane oxidation coupled with hydrogen production.
• To utilize waste acid/base neutralization energy (ENE) for powering the electrochemical process.

Main Methods:

• Utilized a pH-asymmetric electrolyzer with a bipolar membrane.
• Employed NiO-based electrocatalysts for methane oxidation and hydrogen production.
• Investigated catalytic mechanisms using in situ Raman spectroscopy and density functional theory (DFT) calculations.

Main Results:

• Achieved C1/C2 molecule production rates up to 2.6 mmol g_NiO^-1 h^-1 with simultaneous H₂ production at 1.4 V.
• Demonstrated sustained catalysis for over 24 h with a 700 mV lower operation voltage under auxiliary ENE supply, achieving 36.9% energy saving.
• Identified the Ni^III-O^∙-Ni^III-O^- active site as crucial for EOM.
• Showcased high durability with negligible degradation at 10 mA cm^-2.

Conclusions:

• The pH-asymmetric electrolyzer effectively converts waste acid/base into valuable chemicals and hydrogen, offering significant energy savings.
• The developed electrocatalyst and system demonstrate high efficiency, durability, and economic viability for industrial applications.
• This approach provides a pathway for resource recovery from waste acid/base streams and sustainable chemical production.