Engineering Ni(OH)₂ with Pd for Efficient Electrochemical Urea Oxidation

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Urea-assisted water electrolysis offers an energy-efficient alternative to traditional water splitting, with a lower thermodynamic potential.
• Nickel hydroxide (Ni(OH)2) is an effective catalyst, but suffers from active site poisoning by strongly adsorbed CO2, limiting its long-term stability.

Purpose of the Study:

• To investigate the effect of palladium (Pd) incorporation into Ni(OH)2 for urea-assisted water electrolysis.
• To enhance the catalytic efficiency and long-term stability of Ni(OH)2-based electrocatalysts.

Main Methods:

• Synthesis and characterization of Pd-incorporated Ni(OH)2 (Pd/Ni(OH)2) electrocatalysts.
• Electrochemical measurements including overpotential, Tafel slope, and charge transfer resistance.
• X-ray absorption spectroscopy (XAS) to determine metal species.
• Density Functional Theory (DFT) calculations for mechanism exploration.
• Operando Raman and IR spectroscopy to study active sites and intermediates.

Main Results:

• Pd/Ni(OH)2 demonstrated a 40 mV decrease in overpotential at 10 mA cm−2 compared to Ni(OH)2.
• Improved reaction kinetics were indicated by reduced Tafel slope and charge transfer resistance, leading to higher current density (380 mA cm−2 at 1.5 V for Pd/Ni(OH)2 vs. 180 mA cm−2 for Ni(OH)2).
• XAS revealed metallic Pd in the bulk and oxide phase on the surface; DFT and operando spectroscopy elucidated the mechanism and Pd's role in preventing CO2 adsorption.
• Pd incorporation significantly improved catalyst stability to 300 hours.

Conclusions:

• Palladium incorporation effectively enhances the electrocatalytic performance and stability of Ni(OH)2 for urea-assisted water electrolysis.
• The improved performance is attributed to the modified electronic structure and the prevention of CO2 adsorption at active sites by Pd.
• This study presents a promising strategy for developing robust and efficient electrocatalysts for energy conversion applications.