Anion exchange membranes for fuel cells

Innovations in catalyst Engineering enhance the Efficacy of Anion-Exchange Membrane Fuel Cells

Fuel Cells as Energy-Conversion Devices

Fuel Cells serve as energy-conversion devices, producing electricity through electrochemical reactions without combustion, thereby avoiding air pollution. They have the potential to power technologies such as electric vehicles, portable chargers, and industrial machinery.

Challenges with Current Fuel Cell Designs

Although fuel cells offer numerous benefits, many current designs depend on costly materials and precious metal catalysts, hindering their broad adoption. Anion-Exchange-Membrane fuel cells (AEMFCs) present a solution by utilizing Earth-abundant, inexpensive catalysts, potentially making them more accessible.

Recent Advances in AEMFC Research

In recent years, numerous research teams globally have focused on developing and testing new AEMFCs. Although some devices have shown promising outcomes, most non-precious metal catalysts are susceptible to self-oxidation, leading to irreversible cell failure.

Innovative Strategy for Improved Catalysis

A team of researchers form Chongqing University and Loughborough University has recently developed a strategy to prevent the oxidation of metallic nickel electrocatalysts in AEMFCs. This innovative approach, detailed in a Nature Energy paper, involves a quantum well-like catalytic structure (QWCS) composed of quantum-confined metallic nickel nanoparticles.

Quantum Well-Like Catalytic Structures (QWCS)

In their paper, Yuanyuan Zhou, Wei Yuan, and their team discuss how non-precious metals in AEMFCs for hydrogen oxidation are prone to self-oxidation, resulting in irreversible failure. They introduce a quantum well-like catalytic structure (QWCS), incorporating atomically confined nickel nanoparticles within a carbon-doped-MoOₓ/MoOₓ heterojunction (C-MoOₓ/MoOₓ), which selectively transfers external electrons from the hydrogen oxidation reaction while retaining metallic properties.

Features of the Novel QWCS

Quantum well-like catalytic structures (QWCSs) are nanostructures with quantum well characteristics that boost catalytic efficiency. The researchers' novel QWCS features nickel nanoparticles confined within a heterojunction of crystallized carbon-doped MoOₓ (C-MoOₓ) as the low-energy region and amorphous MoOₓ as the high-energy barrier.

Performance of the Ni@C-MoOₓ Catalyst

After 100 hours of rigorous testing, the Ni@C-MoOₓ catalyst showed remarkable stability in HOR and was applied to fabricate an anode-catalyzed alkaline fuel cell. This cell demonstrated a high specific power density of 486 mW mgNi⁻¹ and preserved its performance without degradation following numerous shutdown-start cycles.

Barrier and Performance Metrics

Zhou, Yuan, and their research group noted that the QWCS imparts a 1.11 eV barrier to Ni nanoparticles, maintaining their stability up to 1.2 V vs. VRHE. The QWCS facilitates electron transfer from hydrogen oxidation reactions across this barrier. The QWCS-enhanced AEMFC demonstrated a high power density of 486 mW mgNi⁻¹ and endured hydrogen starvation during shutdown-start cycles, in contrast to the non-QWCS AEMFC, which failed.

Future Implications

The innovative catalytic structure developed by this research team holds promise for advancing cost-effective and durable AEMFCs. Its design strategy, centered around quantum confinement, may also pave the way for other catalysts that effectively mitigate electro-oxidation of non-precious metals.

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