Trapezohedral platinum nanocrystals with high-index facets for high-performance hydrazine electrooxidation

Direct hydrazine fuel cell is a promising portable energy conversion device due to its high energy density and free of carbon emissions. To realize the practical applications, the design of highly efficient electrocatalysts for hydrazine oxidation reaction (HzOR) is crucial. Metal nanocrystals with high-index facets have abundant step sites with reactivity. In this study, we prepared trapezohedral Pt nanocrystals (TPH Pt NCs) enclosed by {311} high-index facets and investigated the catalytic performance for hydrazine oxidation. TPH Pt NCs possess a specific activity of 39.1 mA·cm-2 at 0.20 V, much higher than {111}-faceted octahedral (13.9 mA·cm-2) and {100}-faceted cubic Pt NCs (9.11 mA·cm-2). Meanwhile, TPH Pt NCs also show superior stability. Density functional theory (DFT) calculation indicates that Pt(311) facilitates the deprotonation of N2H4* to N2H3* (the rate-determining step) and improves the HzOR activity. This study is helpful for the design of advanced electrocatalysts for HzOR, especially high-index faceted Pt nanocatalysts.