Durable Natural Urine Electrolysis Enabled by Lewis Acid-Tailored Interfacial Microenvironment

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis
• Renewable Energy

Background:

• Electrochemical urea oxidation (UOR) is a viable alternative to oxygen evolution reaction (OER) for hydrogen production.
• Using natural urine for urine oxidation reaction (U_rOR) offers a cost-free feedstock but faces challenges like catalyst degradation and chloride corrosion.
• Existing catalysts lack stability in complex urine matrices, hindering practical applications.

Purpose of the Study:

• To develop a stable and efficient catalyst for urine oxidation reaction (U_rOR) using natural urine.
• To address catalyst acidification and chloride-induced corrosion issues in U_rOR.
• To demonstrate the feasibility of large-scale hydrogen production from urine electrolysis.

Main Methods:

• Modification of Ni₂P catalyst with hard Lewis acids (LA) to create an interfacial microenvironment.
• Synthesis of V₂O_5-δ-Ni₂P hybrid catalyst.
• Electrochemical testing in natural urine, mechanistic analysis, and verification in a near-kilowatt-scale flow electrolyzer.

Main Results:

• The optimal V₂O_5-δ-Ni₂P hybrid catalyst achieved high U_rOR activity (1.62 V at 3 A cm^-2) and long-term durability (1000 h).
• The Lewis acid component enriched interfacial OH^-, suppressing impurity adsorption (especially Cl^-) and N-chlorourea formation.
• A near-kilowatt-scale flow electrolyzer (18 cells) produced 115.84 L h^-1 H₂ with 97.41% urine purification and recovered NH₄Cl/KCl fertilizers.
• The electrolyzer demonstrated broad applicability across various urea and chloride concentrations, including challenging wastewater effluents.

Conclusions:

• Interfacial microenvironment regulation via Lewis acid modification is an effective strategy for enhancing U_rOR catalyst stability and activity.
• The developed catalyst and system enable efficient, stable hydrogen production from natural urine, coupled with wastewater purification and fertilizer recovery.
• This work validates large-scale urine electrolysis and highlights its potential for sustainable hydrogen generation and resource recovery.