Blue-Pigment Iron Catalyst Reaches 902 mW/cm² Peak in AEMFC Cathode

Researchers from Tohoku University Advanced Institute for Materials Research, Technion – Israel Institute of Technology, Hokkaido University and AZUL Energy have demonstrated a platinum-free cathode catalyst that achieved a peak power density of 902 milliwatts per square centimeter in a laboratory anion-exchange membrane fuel cell, according to Tohoku University and published in ACS Catalysis. That result is the highest reported value for a cathode based on metal phthalocyanine molecules under the tested conditions.

Key Results

The collaboration evaluated two carbon-supported iron tetra-azaphthalocyanine catalysts at an operating cell temperature of 80 °C, and the study reports:

• AZ-FO-30 reached a peak power density of 902 mW/cm² and sustained operation for 35 hours at 400 mA/cm², with an average voltage decay rate of 2.4 mV per hour, according to Tohoku University.
• AZ-FT-30 achieved a peak power density of 744 mW/cm² under identical hydrogen–oxygen testing conditions, the researchers state.

Background

Fuel-cell cathodes have historically depended on platinum-group metals for the oxygen reduction reaction, but platinum is costly and supply is geographically concentrated, according to the US Department of Energy. Anion-exchange membrane fuel cells provide an alkaline environment that can accommodate non-precious catalysts. Still, many promising materials show high half-cell activity yet fall short when installed in full cells, as peer-reviewed reviews have found.

Around 2018, a platinum-free anion-exchange cell using palladium-based catalysts demonstrated nearly 1 W/cm² under optimised laboratory conditions, according to published literature. Subsequent work emphasized durability challenges, citing membrane degradation, carbon corrosion and radical-induced active-site loss as key hurdles.

Institutional Collaboration

The multi-institutional effort was coordinated across four organizations. Professor Hiroshi Yabu at Tohoku University’s Advanced Institute for Materials Research led catalyst synthesis and device integration, drawing on his biomimetics and nanostructured materials expertise. He also serves on the board of AZUL Energy, the Tohoku spin-out founded in 2019 to scale up rare-metal-free catalysts.

At Technion – Israel Institute of Technology, Professor Dario R. Dekel oversaw hydrogen–oxygen fuel cell testing in the Electrochemical Energy based on Membranes Laboratory, while Professor Maytal Caspary Toroker led computational density functional theory analyses. Hokkaido University contributed experimental validation of carbon-supported iron phthalocyanine electrodes under the guidance of Professor Yasutaka Matsuo, confirming the collaborative results reported in ACS Catalysis.

Technical Details

The two catalysts, termed AZ-FT-30 and AZ-FO-30, consist of iron tetra-azaphthalocyanine molecules supported on conductive Ketjen Black carbon. AZ-FT-30 uses a four-nitrogen macrocycle (FeAzPc-4N) and AZ-FO-30 a more nitrogen-rich eight-nitrogen variant (FeAzPc-8N8Me). Catalysts were ink-sprayed onto gas-diffusion layers to form cathodes in an anion-exchange membrane fuel cell running at 80 °C, with pure hydrogen fed to the anode and pure oxygen to the cathode.

According to the researchers, AZ-FT-30 exhibited an electrochemical surface area of about 155.8 m² per gram, while the nitrogen-rich AZ-FO-30 displayed higher intrinsic activity. Density functional theory calculations, incorporating explicit water molecules, indicate that AZ-FO-30’s ligand structure shortens the computed iron–oxygen bond distance for adsorbed hydroxyl intermediates, strengthening catalytic binding.

The Ketjen Black carbon network ensures uniform dispersion of the pigment molecules and provides a highly conductive matrix for electron transport, critical to achieving the reported high current densities. The complete membrane–electrode assembly employed standard anion-exchange membranes and alkaline ionomers, and the balance-of-plant—including bipolar plates and gaskets—was held constant to attribute performance differences solely to the catalyst layer. Test protocols followed widely accepted fuel cell technology benchmarks, facilitating comparability with existing literature on non-precious-metal cathodes.

Strategic Implications

By replacing platinum with iron-containing pigments, these blue catalysts target a significant reduction in material costs and strategic metal dependencies, AZUL Energy indicates. The US Department of Energy classifies platinum-group metals as critical materials with supply-chain vulnerabilities, and broader adoption of non-precious catalysts could diversify sources and mitigate price volatility. In addition, anion-exchange membrane fuel cells can employ less expensive cell hardware—such as stainless steel bipolar plates—instead of costly corrosion-resistant alloys used in acidic proton-exchange systems, peer-reviewed reviews note.

Reaching over 0.9 W/cm² in a platinum-free cathode demonstrates that coordinated molecular design and electrode engineering can meet performance thresholds relevant to automotive and stationary power applications. Lower cost per kilowatt is essential for economic viability in hydrogen infrastructure, and these findings may inform cost models that project system-level savings. However, no lifecycle assessment for the pigment-based catalysts has been disclosed, underscoring the need for comprehensive environmental and economic analyses before commercial deployment.

AZUL Energy envisions extending the pigment platform to metal-air batteries and hydrogen electrolysis technologies, where similar oxygen evolution and reduction chemistry applies. The broader aim is to establish a catalyst portfolio that can support multiple clean hydrogen pathways, aligning with industrial decarbonization and zero-emission technology targets.

Next Steps and Challenges

The reported tests employed pure oxygen at the cathode, whereas practical fuel cells run on ambient air containing nitrogen and trace impurities; mass-transport limitations and nitrogen dilution can reduce effective current density, the study cautions. Carbonate formation from CO₂ in air can foul anion-exchange membranes, and radical species generated at high potentials may degrade both the molecular catalyst and carbon support, industry reviews highlight.

Demonstrating sustained performance under realistic air feeds, frequent start–stop cycling and tolerance to fuel impurities will be critical next steps. Scaling up the synthesis of iron tetra-azaphthalocyanine pigments while maintaining uniform dispersion on conductive supports poses a manufacturing challenge. Researchers also plan to investigate long-duration operation—over hundreds of hours—and assess compatibility with green hydrogen produced by electrolysis, which may contain residual oxygenates or electrolytes.

Comprehensive cost modelling, stack-level engineering and compatibility tests with commercial membranes and balance-of-plant components will be needed to gauge the feasibility of transitioning from lab-scale proofs of concept to pilot-scale stack demonstrations.

Outlook

This collaboration marks a new performance benchmark for metal-phthalocyanine cathodes in anion-exchange membrane fuel cells, according to the authors. While the laboratory demonstration of a platinum-free cathode catalyst reaching 902 mW/cm² is a major step forward, verifying long-term durability, air-fed operation and scalable manufacturing will be decisive for real-world adoption. As hydrogen energy markets expand, sustained research efforts and industry partnerships will determine whether blue-pigment iron catalysts can help lower costs and accelerate the deployment of zero-emission vehicles and stationary power systems within the broader hydrogen infrastructure.