Electrocatalytic Urea Oxidation for Hydrogen Generation

Electrocatalytic urea oxidation leverages the lower thermodynamic potential of urea electrochemical oxidation relative to oxygen evolution to drive hydrogen production with reduced energy input. Urea, abundant in wastewater and industrial effluents, undergoes a six-electron oxidation to yield nitrogen-containing species and protons at the anode, while the cathode facilitates hydrogen evolution. The process not only produces green hydrogen but simultaneously treats urea-containing waste streams. Key challenges include sluggish kinetics of the six-electron transfer, competition from the oxygen evolution reaction, catalyst stability under alkaline conditions and mass transport of reactants and products. Advances in catalyst design—such as alloying, heterostructuring, doping and surface engineering—have been critical in boosting activity, selectivity and long-term durability. Recent efforts have integrated in situ characterisation and theoretical modelling to unravel mechanistic pathways, optimise active site structures and suppress parasitic reactions. The global significance spans decentralised hydrogen generation, wastewater remediation, renewable energy storage and the circular economy.

Research from Nature Portfolio

Recent studies have developed oxyanion-engineered nickel electrocatalysts that inhibit competing oxygen evolution, achieving ultrahigh current densities (>320 mA cm−2) at 1.65 V with >99% selectivity towards urea oxidation and enhanced stability under alkaline conditions. In parallel, composite electrodes comprising nickel phosphide nanocrystals embedded within nickel metal–organic-framework nanosheets on nickel foam have been introduced, requiring only 1.41 V to sustain 100 mA cm−2 for urea oxidation and exhibiting exceptional bifunctional performance for hydrogen evolution at minimal overpotential. These architectures combine self-supporting frameworks and well-exposed active sites, enabling full-cell electrolyser operation at 100 mA cm−2 with a cell voltage of 1.65 V while maintaining stability over extended durations.

Electrocatalytic Urea Oxidation for Hydrogen Generation publication trend

The graph below shows the total number of articles in electrocatalytic urea oxidation for hydrogen generation across all publications each year (not limited to Nature Index journals).

Technical terms

Urea oxidation reaction (UOR): Electrochemical oxidation of urea to nitrogen-containing products, releasing electrons and protons at the anode.

Hydrogen evolution reaction (HER): Electrochemical reduction of protons to molecular hydrogen at the cathode.

Overpotential: Additional voltage beyond the thermodynamic potential required to drive an electrochemical reaction at a desired rate.

Current density: Electric current per unit electrode area, indicating reaction rate and catalyst activity.

Faradaic efficiency: Fraction of total charge that contributes to the intended electrochemical reaction rather than side processes.

Electrocatalyst: Material that lowers the activation energy for electrochemical reactions, enhancing reaction rates and selectivity.

References

1. Strong electronic coupling of CoNi and N‐doped‐carbon for efficient urea‐assisted H2 production at a large current density. Carbon Energy (2023).
2. Identification and manipulation of dynamic active site deficiency-induced competing reactions in electrocatalytic oxidation processes. Energy & Environmental Science (2022).
3. Boosting urea electrooxidation on oxyanion-engineered nickel sites via inhibited water oxidation. Nature Communications (2023).
4. Directed Urea‐to‐Nitrite Electrooxidation via Tuning Intermediate Adsorption on Co, Ge Co‐Doped Ni Sites. Advanced Functional Materials (2023).
5. Ni2P nanocrystals embedded Ni-MOF nanosheets supported on nickel foam as bifunctional electrocatalyst for urea electrolysis. Scientific Reports (2021).