Fuel cells are becoming increasingly popular as an energy-conversion solution due to their ability to generate electricity through electrochemical reactions without contributing to air pollution. These cells have the potential to power a wide range of technologies, from electric vehicles to industrial machines. However, one of the main challenges facing fuel cell technology is the reliance on expensive materials and precious metal catalysts, which hinders their widespread adoption.
Anion-exchange-membrane fuel cells (AEMFCs) offer a promising solution to this challenge by utilizing Earth-abundant, low-cost catalysts. Research groups around the world have been working on designing and testing new AEMFCs in recent years. While some devices have shown promising results, most non-precious metal catalysts have been found to be susceptible to self-oxidation, leading to irreversible failure of the cells.
Recently, researchers at Chongqing University and Loughborough University have developed a groundbreaking strategy to prevent the oxidation of metallic nickel electrocatalysts in AEMFCs. Their innovative approach involves the use of a quantum well-like catalytic structure (QWCS) made up of quantum-confined metallic nickel nanoparticles. This structure, as described in a paper in Nature Energy, allows for the selective transfer of external electrons from the hydrogen oxidation reaction while keeping the nickel catalyst metallic and preventing self-oxidation.
The researchers’ QWCS consists of nickel nanoparticles confined within a heterojunction composed of crystallized carbon-doped MoOx (C-MoOx) as the low energy valley and amorphous MoOx as the high energy barrier. The catalyst, known as Ni@C-MoOx, can efficiently transfer electrons produced during the hydrogen oxidation reaction without allowing electrons to flow from the nickel catalyst into the QWCS’ valley. This selective electron transfer ensures the catalyst’s stability against electro-oxidation, protecting fuel cells from degradation and failure.
The Ni@C-MoOx catalyst demonstrated excellent catalytic stability in the hydrogen oxidation reaction, maintaining its performance after 100 hours of continuous operation under harsh conditions. When used to create an anode-catalyzed alkaline fuel cell, the fuel cell exhibited a high specific power density of 486 mW mgNI-1, with no decline in performance following repeated shutdown-start cycles. The QWCS-catalyzed AEMFC outperformed a counterpart AEMFC without the QWCS, proving the effectiveness of the new catalytic structure.
The innovative design of the QWCS by the team of researchers opens up possibilities for developing cost-effective and reliable AEMFCs that do not degrade rapidly over time. The underlying design strategy could also be applied to create other catalysts that leverage quantum confinement to prevent the electro-oxidation of non-precious metals. This breakthrough in catalyst design marks a significant step forward in the development of efficient and sustainable fuel cell technology.