Ni-Zr alloys: relationship between surface characteristics and electrocatalytic behavior

Area of Science:

• Materials Science
• Electrochemistry
• Surface Science

Background:

• The hydrogen evolution reaction (HER) is crucial for sustainable energy technologies.
• Understanding the relationship between electrode surface composition and HER activity is vital for catalyst development.
• Nickel-Zirconium (Ni-Zr) alloys present potential as electrocatalysts, but their surface properties require detailed investigation.

Purpose of the Study:

• To establish a correlation between the surface composition of Ni-Zr crystalline and amorphous alloys and their electrocatalytic activity for the HER.
• To investigate the effects of surface activation treatments on the morphology and composition of Ni-Zr alloys.
• To elucidate the mechanisms behind enhanced electrocatalytic performance.

Main Methods:

• Secondary ion mass spectrometry (SIMS) for surface composition analysis.
• Cathodic polarization in 1 M KOH at 25°C to measure electrocatalytic activity (exchange current density).
• Differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM) to study surface changes after chemical etching in hydrofluoric acid (HF) solutions.

Main Results:

• Chemical etching in HF solutions consistently increased the electrocatalytic activity for HER across all Ni-Zr alloy samples.
• The alloy with the highest nickel content exhibited the most significant improvement in HER activity post-etching.
• SIMS and other surface analysis techniques revealed that etching dissolved the zirconium oxide layer and promoted the formation of nanocrystalline nickel on the surface.

Conclusions:

• The surface composition, particularly the presence of nickel and the absence of zirconium oxides, is a key factor in determining HER electrocatalytic efficiency for Ni-Zr alloys.
• Chemical etching is an effective surface activation strategy for Ni-Zr alloys, enhancing their HER performance.
• The formation of a nanocrystalline nickel surface is responsible for the improved electrocatalytic activity observed after etching.