Transient-Promoter-Stabilized NiFe Oxyhydroxide Enables Durable kW-Scale Water Splitting Under Fluctuating Power

Area of Science:

• Electrochemistry
• Materials Science
• Renewable Energy

Background:

• Renewable energy integration for hydrogen production via water electrolysis is crucial for decarbonization.
• Current systems rely on stable grid electricity, limiting direct use of fluctuating renewable power.
• Durable catalysts and devices are needed to withstand dynamic operating conditions in renewable-powered electrolyzers.

Purpose of the Study:

• To develop a transient-promoter strategy for nickel-iron (NiFe) oxyhydroxide oxygen evolution reaction (OER) catalysts.
• To enable kilowatt-scale anion exchange membrane water electrolyzers (AEMWEs) for direct renewable power integration.
• To enhance catalyst stability and performance under dynamic operational loads.

Main Methods:

• Synthesis of NiFe oxyhydroxide catalysts using a Ni3Fe1.2Cr0.8Ox precursor with a transient-promoter strategy.
• Characterization using ex situ and operando spectroscopy to understand chromium's role.
• Testing of lab-scale AEMWE devices and scaling up to an 8-cell, 512 cm2 stack.
• Evaluation of performance under constant and fluctuating loads, including simulated solar cycles.

Main Results:

• Chromium (Cr) acts as a transient promoter, modulating Ni/Fe oxidation states, inducing porosity, and sacrificially leaching to protect active sites.
• Lab-scale AEMWE achieved 1 A cm-2 at 1.68 V, maintaining operation for over 30 days under dynamic loads.
• A 2.5 kW stack demonstrated 1 A cm-2 at 1.78 V per cell and resilience over 50 hours of simulated solar cycles.

Conclusions:

• The transient-promoter strategy significantly enhances the durability and performance of NiFe oxyhydroxide OER catalysts in AEMWEs.
• This approach facilitates the direct integration of fluctuating renewable electricity sources for efficient hydrogen production.
• The developed system shows strong feasibility for large-scale, carbon-neutral hydrogen generation.