An important low-carbon technology is the hydrogen fuel cell, which can be used in vehicles, backup power systems and other applications. Fuel cells convert hydrogen into electricity, producing only water as a by-product. A key process inside the cell is the oxygen reduction reaction, in which oxygen from the air is reduced at the cathode. This reaction is relatively slow and is one of the main factors limiting fuel-cell performance.

To speed up this step, platinum catalysts are used. While highly effective, platinum is expensive and gradually degrades during operation. Much research therefore focuses on reducing the amount of platinum required while improving performance and catalyst lifetime. One approach is to use platinum alloys, where a cheaper metal is mixed with platinum to improve efficiency. However, these alloying metals can gradually leach out, causing the catalyst to lose activity over time.

In this work, the researchers aimed to address the trade off between catalytic activity and long-term durability by investigating two alloy catalysts, platinum-copper (PtCu) and platinum-iron (PtFe). These were attached to a two-dimensional material, similar to graphene, called a MXene, which can improve performance while helping to hold the nanoparticles in place and enhance their stability. PtCu/MXene showed the highest catalytic activity, as copper modifies the platinum surface to improve oxygen reduction and accelerate the reaction. PtFe/MXene was less active but more durable, with strong Fe-O-MXene interactions helping to stabilise the catalyst during long-term operation.

By using in-situ X-ray spectroscopy, the researchers were able to observe the catalysts during operation and identify the structural and electronic changes responsible for their performance. This revealed how alloy composition and catalyst supports influence activity and durability, the study provides a roadmap for developing improved catalysts for future fuel cells.

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Catalyst designing strategies for electrochemical CO2 reduction: a perspective by Shreya Sarkar and Sebastian C Peter (2022)