Double Hydroxide Nanocatalysts for Urea Electrooxidation Engineered toward Environmentally Benign Products

Area of Science:

• Electrochemistry
• Materials Science
• Environmental Chemistry

Background:

• Electrochemical urea oxidation (UOR) is crucial for wastewater remediation and energy recovery.
• Controlling UOR products to avoid environmentally harmful byproducts remains a challenge due to limited structure-selectivity understanding.
• Nickel (Ni) and copper (Cu) double hydroxides exhibit distinct reactivity and selectivity in UOR.

Purpose of the Study:

• To evaluate the UOR performance of Ni and Cu double hydroxides.
• To elucidate the structure-selectivity relationships governing UOR product formation.
• To identify catalyst design principles for achieving innocuous UOR products.

Main Methods:

• Electrochemical performance testing of CuCo and NiCo hydroxides.
• In-situ spectroscopy and scattering experiments to probe active sites and reaction mechanisms.
• Analysis of reaction products to determine selectivity.

Main Results:

• CuCo hydroxides predominantly produce nitrogen (N₂) with high current density at a lower potential compared to NiCo hydroxides.
• NiCo hydroxides generate nitrogen oxides, attributed to high-valence Ni species and hydroxyl ion accumulation.
• In-situ generated Cu^(2-x)+-OO^-• active sites in CuCo facilitate N-N coupling for N₂ formation.

Conclusions:

• Catalyst composition and structural engineering are critical for directing UOR towards benign products like N₂.
• Understanding in-situ active sites is key to designing selective electrocatalysts for urea oxidation.
• CuCo hydroxides offer a promising pathway for efficient and selective electrochemical urea oxidation.