Climbing the Hydrogen Evolution Volcano with a NiTi Shape Memory Alloy.

Area of Science:

• Electrochemistry
• Materials Science
• Sustainable Energy

Background:

• Alkaline water electrolysis offers a sustainable route to green hydrogen production using renewable energy.
• The hydrogen evolution reaction (HER) kinetics are significantly slower in alkaline media compared to acidic conditions.
• Non-precious metal catalysts are desirable for alkaline HER due to cost-effectiveness.

Purpose of the Study:

• To identify a facile method for enhancing the alkaline hydrogen evolution reaction (HER) performance.
• To investigate the potential of commercially available NiTi shape memory alloys as efficient HER electrocatalysts.

Main Methods:

• Utilized commercially available NiTi shape memory alloys, exploiting their phase transformation from martensite to austenite upon heating.
• Evaluated HER performance of austenitic NiTi compared to platinum (Pt) electrocatalysts.
• Employed density functional theory (DFT) calculations to analyze the surface structure and hydrogen binding energies of the austenite phase.

Main Results:

• Austenitic NiTi demonstrated significantly improved HER performance at 80 °C, outperforming state-of-the-art Pt catalysts by up to 50% in current density.
• Room-temperature performance of NiTi was modest, highlighting the temperature-dependent catalytic activity.
• DFT computations revealed that the austenite phase's surface ensembles exhibit optimal hydrogen binding energies for HER, weaker than metallic Ni or Ti alone.

Conclusions:

• NiTi shape memory alloys, particularly in their austenite phase, represent a promising non-precious metal catalyst for efficient alkaline HER.
• The facile phase transformation and superior performance at elevated temperatures make NiTi an attractive alternative to precious metal catalysts for green hydrogen production.