High spin polarization ultrafine Rh nanoparticles on CNT for efficient electrochemical N2 fixation to ammonia.

[Display omitted] • High spin polarized ultrafine Rh nanoparticles/CNT is designed and synthesized. • Rh/CNT is efficient and stable nitrogen reduction reaction catalyst. • Electrolyte adjustment is used to optimize catalytic performances. • High spin electron state of Rh/CNT improves the activity for nitrogen reduction. The electroreduction of nitrogen (N 2) to ammonia (NH 3) is gravely restricted by its inherent kinetic complexity and energy-intensive multi-electron steps. Most literature has reported that the first step of N 2 adsorption and activation is the bottleneck of electrochemistry N 2 reduction reaction (NRR). However, it is a considerable challenge to understand the design rule of catalysts with perfect performances for NRR. Here, as a proof-of-concept experiment, we apply the theoretical calculations with the experimental studies to reveal the influence of the high spin related to the size effect and the charge density related to the substrate effect on the catalytic activity of NRR catalysts. The desired ultrafine Rh nanoparticles anchored on CNT exhibit excellent NRR performances, especially high NH 3 yield (26.91 μg h−1 mg cat. −1), Faradaic efficiency (23.48 %) and energy efficiency (20.50 %), outperforming most reported NRR electrocatalysts under ambient conditions, which can be attributed to excellent synergism of the high-spin polarization of Rh NPs and the charge exchange between Rh NPs and the substrate that can promote N 2 adsorption and activate its intrinsic N N triple bond. [ABSTRACT FROM AUTHOR]