Enhancing Ni/Co Activity by Neighboring Pt Atoms in NiCoP/MXene Electrocatalyst for Alkaline Hydrogen Evolution

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Platinum (Pt) is known to enhance the activity of nickel cobalt phosphide (NiCoP) for the hydrogen evolution reaction (HER).
• Integrating Pt with NiCoP presents a significant synthetic challenge.
• Curved, bowl-like structures can facilitate the interface between Pt and NiCoP.

Purpose of the Study:

• To construct a Pt/NiCoP interface using a minimal amount of Pt (1‰ molar ratio) within a bowl-like structure.
• To investigate the enhanced catalytic activity and stability of the novel Pt/NiCoP material for HER.
• To elucidate the underlying mechanism of enhanced HER performance through experimental and theoretical analyses.

Main Methods:

• Synthesis of Pt/NiCoP catalyst with a focus on creating a specific interface.
• Electrochemical characterization including overpotential measurements at specific current densities and long-term stability tests.
• Spectroscopic techniques (XPS, sXAS, XAFS) and theoretical calculations (DFT) to analyze electronic structure and reaction pathways.
• In situ electrochemical impedance spectroscopy (EIS) and scanning electrochemical microscopy (SECM) to probe interfacial properties.

Main Results:

• The Pt/NiCoP catalyst achieved low overpotentials of 26.5 mV (10 mA cm⁻²) and 181.6 mV (500 mA cm⁻²) in 1 M KOH.
• A significant decrease (~43%) in water dissociation energy barrier (Ea) was observed compared to NiCoP.
• Exceptional stability was demonstrated with a degradation rate of 10.6 μV h⁻¹ at 500 mA cm⁻² and 50°C over 3000 hours.
• Interface electron transfer lowered the valence state of Co/Ni, activating the catalyst.
• DFT calculations confirmed a shift in the catalytic step from Heyrovsky (2.71 eV) to Tafel (0.51 eV) near Pt, consistent with improved H ads.

Conclusions:

• The introduction of a minimal Pt amount onto a curved NiCoP structure effectively creates an active interface for HER.
• The Pt/NiCoP catalyst exhibits superior activity, efficiency, and durability for hydrogen production.
• The enhanced performance is attributed to interfacial electron transfer and modified reaction pathways, as confirmed by experimental and theoretical studies.