Double-Heterostructured Nickel Phosphate-Phosphides as High-Activity Electrocatalyst for Ammonia Borane...

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Direct electrooxidation of ammonia borane (ABOR) is crucial for direct ammonia borane fuel cells (DABFCs).
• Electrocatalyst properties, including active sites and charge/mass transfer, critically influence ABOR kinetics and thermodynamics.
• Optimizing electrocatalysts is key to enhancing DABFC performance.

Purpose of the Study:

• To develop a novel double-heterostructured catalyst for improved ABOR.
• To investigate the structure-activity relationship of the new catalyst.
• To evaluate the electrocatalytic performance of the designed catalyst for DABFCs.

Main Methods:

• Synthesis of a double-heterostructured Ni₂P/Ni₂P₂O₇/Ni₁₂P₅ (d-NPO/NP) catalyst.
• Characterization of the catalyst's electronic structure and active sites.
• Electrochemical evaluation of the catalyst's activity towards ABOR.
• Density Functional Theory (DFT) computations to understand catalytic mechanisms.

Main Results:

• The d-NPO/NP-750 catalyst exhibited outstanding electrocatalytic activity for ABOR, with an onset potential of -0.329 V vs RHE.
• DFT calculations revealed that Ni₂P₂O₇/Ni₂P enhances activity via a high d-band center and low activation energy.
• Ni₂P₂O₇/Ni₁₂P₅ acts as a conductivity-enhancing heterostructure with high valence electron density.

Conclusions:

• The d-NPO/NP catalyst represents a significant advancement in electrocatalyst design for ABOR.
• The synergistic effects within the heterostructure optimize electron distribution and active site accessibility.
• This catalyst shows great promise for improving the efficiency of direct ammonia borane fuel cells.