Dynamic Decoupling of Pt─H Intermediates Formation From Water Dissociation for Efficient Alkaline Hydrogen Evolution

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• The alkaline hydrogen evolution reaction (HER) is crucial for clean energy, but its efficiency is limited by the slow, energy-intensive water dissociation step.
• Formation of metal-hydrogen intermediates (M─H*) is essential for HER, yet hindered by kinetic barriers.

Purpose of the Study:

• To investigate a new pathway for generating M─H* intermediates that circumvents water dissociation.
• To develop a highly active and stable catalyst for alkaline HER using a metal hydride support.

Main Methods:

• Operando differential electrochemical mass spectrometry (DEMS) and in situ Raman spectroscopy were employed to study the reaction mechanism.
• Fabrication and testing of platinum nanoparticles supported on TiH_1.924 (Pt/TiH_1.924) as a model catalyst.
• Evaluation of the catalyst's performance in an anion exchange membrane water electrolyzer.

Main Results:

• A distinct pathway was identified where lattice hydrogen from TiH_1.924 directly forms Pt─H* intermediates, bypassing water dissociation.
• The Pt/TiH_1.924 catalyst exhibited a 35.6-fold higher mass activity compared to Pt/C at 100 mV overpotential.
• An electrolyzer using Pt/TiH_1.924 achieved a low cell voltage of 1.76 V at 1 A cm^-2 and stable operation for over 1000 hours.

Conclusions:

• A lattice hydrogen-mediated mechanism significantly enhances alkaline HER by decoupling M─H* formation from water dissociation.
• Metal hydride supports offer a promising strategy to overcome kinetic limitations in HER and other electrochemical processes.
• The Pt/TiH_1.924 catalyst demonstrates potential for efficient and durable hydrogen production in alkaline media.