Semimetal-induced covalency achieves high-efficiency electrocatalysis for platinum intermetallic compounds

Compared with other types of batteries, proton exchange membrane fuel cells have the advantages of high discharge power and no pollution, which is also an important carrier for hydrogen energy conversion and utilization. Platinum intermetallic compounds play an important role as electrocatalysts in a series of energy and environmental technologies such as proton exchange membrane fuel cells.

However, the process for synthesis of platinum intermetallic compounds needs to be reorganized into ordered Pt–M metal bonds driven by high temperature (~600°C), which usually has great side effects on the structure of the catalyst, such as the uneven distribution of size, morphology, composition and structure, which further affects the performance of the catalyst and batteries.

In response to this challenge, Professor Changzheng Wu’s group at the University of Science and Technology of China introduced semimetal atoms, such as Ge, Sb, Te into the synthesis process of platinum-based intermetallic compounds. The research is published in the journal National Science Review.

The chemical bonds formed between semimetal elements and platinum atoms (Pt–Ge, Pt–Sb, Pt–Te) have both characteristics of metallic and covalent bonds, thus breaking the limitation of the synthesis temperature for platinum intermetallic compounds. It is also beneficial to the electrocatalytic reaction of proton exchange membrane fuel cells.

Due to the partial filling of p orbitals in the metallization elements, the d-p π feedback bond is formed between platinum and semimetal atoms as a strong covalent interaction. This force can be used as a driving force to promote the ordering arrangement in the high-temperature synthesis process of intermetallic compounds, thus breaking the temperature limit for the synthesis of platinum intermetallic compounds.

In addition, the characteristics of both metallic bonds and covalent bonds can further promote the electron transfer and orbital filling of platinum active sites in the fuel cells, so as to achieve the improvement of catalytic activity and anti-toxic ability.

The semimetal-platinum intermetallic compounds can be synthesized at only 300°C, and they show extremely high oxygen reduction activity under CO toxicity in fuel cell electrochemical tests (mass activity of 0.794 A mg⁻¹ at 0.9 V voltage, attenuation of 5.1% under CO toxicity), which is 11 times that of commercial Pt/C catalysts.

This study realizes bonding and orbital optimization in fuel cell catalyst synthesis and working conditions by introducing semimetals, and provides new insights for rational design of advanced electrocatalysts for fuel cells.

More information:
Han Cheng et al, Semimetal-triggered covalent interaction in Pt-based intermetallics for fuel-cell electrocatalysis, National Science Review (2024). DOI: 10.1093/nsr/nwae233