Constructing CoNi-LDH/Fe MOF/NF Heterostructure Catalyst for Energy-Efficient OER and UOR at High Current Density

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Sluggish oxygen evolution reaction (OER) kinetics necessitate high overpotentials, increasing energy consumption in water electrolysis for hydrogen production.
• Developing efficient electrocatalysts is crucial to overcome these limitations and enable cost-effective hydrogen generation.

Purpose of the Study:

• To design and synthesize a novel CoNi-LDH/Fe MOF/NF heterostructure catalyst with nanoneedle array morphology.
• To evaluate the electrocatalytic performance of the heterostructure for the oxygen evolution reaction (OER) and urea oxidation reaction (UOR).
• To investigate the potential of urea oxidation reaction (UOR) as a more energy-efficient alternative to OER in overall urea splitting (OUS).

Main Methods:

• Fabrication of a CoNi-LDH/Fe MOF/NF heterostructure catalyst on nickel foam (NF).
• Electrochemical characterization of the catalyst's performance in 1.0 M KOH solution for OER and UOR.
• Comparison of catalytic activities with single-component catalysts (CoNi-LDH/NF and Fe MOF/NF).
• Evaluation of overall urea splitting (OUS) and overall water splitting (OWS) in a two-electrode electrolytic cell.

Main Results:

• The CoNi-LDH/Fe MOF/NF heterostructure catalyst achieved low overpotentials of 275 mV and 305 mV at current densities of 500 and 1000 mA/cm², respectively, for OER.
• The heterostructure catalyst exhibited significantly higher activity than individual CoNi-LDH/NF and Fe MOF/NF catalysts, attributed to synergistic effects.
• Replacing OER with UOR reduced overpotentials by 80 mV and 40 mV at the same current densities.
• Overall urea splitting (OUS) required a cell voltage of 1.55 V at 100 mA/cm², which is 60 mV lower than that for overall water splitting (OWS).

Conclusions:

• The rational design of heterostructure catalysts, like CoNi-LDH/Fe MOF/NF, can significantly enhance electrocatalytic performance.
• Utilizing the urea oxidation reaction (UOR) instead of OER in water electrolysis can substantially decrease energy consumption.
• This study presents a promising strategy for efficient and low-cost hydrogen production through electrocatalysis.