Coherent hexagonal platinum skin on nickel nanocrystals for enhanced hydrogen evolution activity

Metastable noble metal nanocrystals may exhibit distinctive catalytic properties to address the sluggish kinetics of many important processes, including the hydrogen evolution reaction under alkaline conditions for water-electrolysis hydrogen production. However, the exploration of metastable noble metal nanocrystals is still in its infancy and suffers from a lack of sufficient synthesis and electronic engineering strategies to fully stimulate their potential in catalysis. In this paper, we report a synthesis of metastable hexagonal Pt nanostructures by coherent growth on 3d transition metal nanocrystals such as Ni without involving galvanic replacement reaction, which expands the frontier of the phase-replication synthesis. Unlike noble metal substrates, the 3d transition metal substrate owns more crystal phases and lower cost and endows the hexagonal Pt skin with substantial compressive strains and programmable charge density, making the electronic properties particularly preferred for the alkaline hydrogen evolution reaction. The energy barriers are greatly reduced, pushing the activity to 133 mA cm(geo)(-2) and 17.4 mA mu g(Pt)(-1) at -70 mV with 1.5 mu g of Pt in 1 M KOH. Our strategy paves the way for metastable noble metal catalysts with tailored electronic properties for highly efficient and cost-effective energy conversion. Synthesis and modulation of metastable noble metal nanocrystal catalysts is interesting yet challenging. Here the authors report synthesis of metastable hexagonal Pt skins on Ni nanocrystals with modulated electronic structures and enhanced hydrogen evolution activities.

Automated summary

This study reports a method for synthesizing metastable hexagonal Pt nanostructures on 3d transition metal nanocrystals without involving galvanic replacement reaction, expanding the frontier of phase-replication synthesis. Compared to noble metal substrates, the 3d transition metal substrate has more crystal phases and lower cost, providing the hexagonal Pt skin with compressive strains and programmable charge density, making it particularly suitable for the alkaline hydrogen evolution reaction. The energy barriers are greatly reduced, resulting in high activity for hydrogen evolution. This strategy paves the way for tailored electronic properties of metastable noble metal catalysts for efficient and cost-effective energy conversion.