How Size and Strain Effect Synergistically Improve Electrocatalytic Activity: A Systematic Investigation Based on PtCoCu Alloy Nanocrystals

To reveal how the size effect and strain effect synergistically regulate the mass activity (MA) and specific activity (SA) of Pt alloy nanocrystal catalysts in oxygen reduction reaction (ORR), remains to be difficult due to the highly entangled factors. In this work, six ternary PtCoCu catalysts with sequentially changed composition, size, and compression strain are prepared. It is found that the smaller the alloy particles, the higher the electrochemical active surface area (ECSA) and MA values, that is, the particle size plays a decisive role in the size of the ECSA and MA. While, along alloy size decrease, the intrinsic activity SA first increases, then remains unchanged, and finally rapidly increases again. This detailed analysis shows that for the alloys above 4 nm, it is the surface coordination number that decides the SA, while for those below 4 nm, it is the well-regulated compression strain that determines the SA. Particularly, Pt47Co26Cu27 demonstrates the MA of 1.19 A mg(Pt)(-1) and SA of 1.48 mA cm(-2), being 7.9 and 6.4 times those of commercial Pt/C respectively, representing an especially superior ORR catalyst.

Automated summary

The article discusses the regulation of the mass activity and specific activity of Pt alloy nanocrystal catalysts in the oxygen reduction reaction (ORR) by the size effect and strain effect. The particle size plays a decisive role in the electrochemical active surface area (ECSA) and mass activity (MA), while the surface coordination number and compression strain determine the specific activity (SA). Pt47Co26Cu27 is identified as a superior ORR catalyst with high MA and SA values.