Exposed facet-controlled N ₂ electroreduction on distinct Pt ₃Fe nanostructures of nanocubes, nanorods and nanowires

Abstract

Understanding the correlation between exposed surfaces and performances of controlled nanocatalysts can aid effective strategies to enhance electrocatalysis, but this is as yet unexplored for the nitrogen reduction reaction (NRR). Here, we first report controlled synthesis of well-defined Pt ₃Fe nanocrystals with tunable morphologies (nanocube, nanorod and nanowire) as ideal model electrocatalysts for investigating the NRR on different exposed facets. The detailed electrocatalytic studies reveal that the Pt ₃Fe nanocrystals exhibit shape-dependent NRR electrocatalysis. The optimized Pt ₃Fe nanowires bounded with high-index facets exhibit excellent selectivity (no N ₂H ₄ is detected), high activity with NH ₃ yield of 18.3 μg h ⁻¹ mg ⁻¹ _cat (0.52 μg h ⁻¹ cm ⁻² _ECSA; ECSA: electrochemical active surface area) and Faraday efficiency of 7.3% at −0.05 V versus reversible hydrogen electrode, outperforming the {200} facet-enclosed Pt ₃Fe nanocubes and {111} facet-enclosed Pt ₃Fe nanorods. They also show good stability with negligible activity change after five cycles. Density functional theory calculations reveal that, with high-indexed facet engineering, the Fe-3d band is an efficient d-d coupling correlation center for boosting the Pt 5d-electronic exchange and transfer activities towards the NRR.

Abstract

We have reported facile synthesis of Pt ₃Fe nanocrystals with tunable morphologies (nanocubes, nanorods and nanowires) to evaluate the performance of N ₂ electroreduction on different exposed surface structures.