Currently Pt/Ni alloy ^[1] and de-alloyed ^[2] Pt/Ni nanoparticles, and the 3M nanostructured thin film catalyst of de-alloyed Pt/Ni films on whiskers ^[3] are some of the few to have met the DoE 2020 mass activity target of 0.44 A/mg Pt at 0.9 VIR free. The origin of the extraordinary activity shown by the Ni/Pt system is attributed to a delicate balance between a thin Pt shell and the sub-surface Ni content ^[1]. One approach to the preparation of highly active Ni/Pt electrocatalysts is by galvanic displacement of Ni from nanofibres with platinum ^[4]. We have recently found that is possible to reduce significantly the reaction time for Pt-Ni galvanic displacement by using a microwave-assisted procedure on Ni nanofibres, which leads to high mass activity catalysts (>0.5 A/mg Pt) in only 2 minutes. The shell thickness and density are controlled by extent of Ni/Pt displacement (Pt loading), itself controlled by the concentration of Pt ions in solution. By tuning the Pt content, Pt/Ni core/shell electrocatalysts were prepared that do not require electrochemical etching of surface Ni or de-alloying before utilisation. In addition the nickel core can be leached leaving chemically stable Pt₄Ni thin tubular structure.

References:

[1] V. R. Stamenkovic, B. Fowler, B. S. Mun, G. Wang, P. N. Ross, C. A. Lucas and N. M. Marković, Science 315 493–497 (2007).

[2] P. Strasser and S. Kühl, Nano Energy 26 1–12 (2016).

[3] M. K. Debe, R. T. Atanasoski and A. J. Steinbach, ECS Trans. 41 937–954 (2011).

[4] S. M. Alia, Y. S. Yan and B. S. Pivovar, Catal. Sci. Technol. 4 3589–3600 (2014).

Acknowledgement: This project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement No 700127 INSPIRE. This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation programme.