Research team develops new platinum-nickel core-shell catalyst to improve fuel cell efficiency

Electrocatalysis is a key technology in the field of sustainable energy, so understanding how catalysts work is important to improving their performance. Part of the challenge of using platinum (Pt) as a catalyst for the oxygen reduction reaction (ORR) in fuel cells is that the reaction is too slow and not efficient enough. A promising solution is to tune the catalyst surface to increase its activity.

(Image source: Tohoku University, Japan)

"We can improve performance by tuning the surface structure of platinum, helping it to react more efficiently," said Di Zhang, assistant professor at the Advanced Materials Research Institute (WPI-AIMR) at Tohoku University in Japan. This surface tuning, called surface strain, occurs when the arrangement of atoms at the surface of a material is compressed or expanded. An example is the Pt-Ni system, in which platinum is paired with nickel to improve performance.

Zhang said that while studies have shown that Pt-Ni performs well, “many studies have not fully explored which parts of the material are actually responsible for the reaction process. Also, none of these models take into account how pH affects the reaction, which is a critical factor in practical applications.”

To solve this problem, Zhang and an international team of researchers created a new model that takes into account the real conditions of electrochemical reactions. The model was used to design a new Pt-Ni catalyst with a core-shell structure, called Pt1Ni1@Pt/C.

The results showed that the new catalyst had significantly improved activity compared to traditional platinum catalysts. "We found that the mass activity of Pt1Ni1@Pt/C was 1.424±0.019 A/mgPt and the specific activity was 1.554±0.027 mA/cmPt²," said Hao Li, assistant professor at WPI-AIMR.

The new catalyst proved to be very durable, retaining 98.4% of its activity even after 70,000 cycles. In addition, the researchers anchored tiny Pt-Ni nanoparticles (about 2.6 nm) to the carbon matrix using a special method, forming a bond that prevents the particles from moving or clumping together.

They then created a Pt-rich shell around the Pt-Ni core, which applied compressive strain to help improve the catalyst's ability to adsorb oxygen, making the reaction more efficient. This core-shell design (along with the improved surface strain) contributes to the catalyst's superior performance and durability.

"This study shows that by combining new models, innovative material design and advanced synthesis techniques, Pt-Ni catalysts can be made more efficient and stable for use in energy technologies," said researcher Li. Ultimately, this research will open the door to developing more durable catalysts that could play an important role in future renewable energy applications.