Reactive Ionic Liquid Enables the Construction of 3D Rh Particles with Nanowire Subunits for Electrocatalytic Nitrogen Reduction

Abstract

Until now, the synthesis of Rh particles with unusual three‐dimensional (3D) nanostructures is still challenging. A 3D nanostructure enables fast ion/molecule transport and possesses plenty of exposed active surface, and therefore it is of great interest to construct 3D Rh particles catalysts for the N2 reduction reaction (NRR). Herein, we proposed a reactive ionic liquid strategy for fabricating unusual 3D Rh particles with nanowires as the subunits. The ionic liquid n‐octylammonium formate simultaneously worked as reaction medium, reductant and template for the successful construction of 3D Rh particles. The as‐prepared 3D Rh particles demonstrated excellent activity for electrocatalytic N2 fixation in 0.1 M KOH electrolyte under ambient conditions with a high NH3 yield of 35.58 μg h−1 mgcat.−1 at −0.2 V versus reversible hydrogen electrode (RHE), surpassing most of the state‐of‐the‐art noble metal catalysts. Our reactive ionic liquid strategy thus holds great promise for the rational construction of high‐performance electrocatalysts toward NRR.

Electrocatalytic Reduction of Nitrogen to Ammonia in Ionic Liquids

“…In the study, they also selected the IL OAF as the solvent, reductant, and template, and the formic anion of IL first reduced Rh 3+ and then the template function of IL fabricated the final 3D Rh nanostructure with nanowires subunits. 40 Note that the performances of the electrocatalytic NRR were improved effectively in both studies.…”

“…In 2020, the authors once again adopted an ILs strategy to synthesize 3D Rh particles with nanowire subunits which possess more active sites and provide more transfers channels for ions or electrons (as shown in Figure ). In the study, they also selected the IL OAF as the solvent, reductant, and template, and the formic anion of IL first reduced Rh 3+ and then the template function of IL fabricated the final 3D Rh nanostructure with nanowires subunits . Note that the performances of the electrocatalytic NRR were improved effectively in both studies.…”

“…At present, the main strategies to improve the reaction activity and FE include two aspects: (1) NRR catalysts design, which mainly includes the structure optimization, − heteroatomic doping, , defect engineering, − surface/interface engineering, − and synergistic effects and (2) catalytic system integration, mainly including the modification of the electrolytes. Often the specific ions are introduced into the electrolyte or add ionic liquids (ILs) to electrolytes, and even the pure ILs are used as electrolytes to improve the solubility of N 2 or suppress the competition reaction of HER − as well as the improvement of NH 3 yields. There are several review papers summarizing the NRR process; ,− however, the combination of electrocatalytic NRR process and ILs are somehow few.…”

An Overview on Noble Metal (Group VIII)‐based Heterogeneous Electrocatalysts for Nitrogen Reduction Reaction

“…Thus, it is important to establish 3D Rh particulate catalysts that also act in this way for NRR. Recently, 3D Rh particles were prepared in a one‐step method using the ionic liquid, [29a] which acted as reductants, structural‐guiding agents, and reaction media for the growth of the 3D Rh particles. The as‐grown 3D Rh particulate catalysts proved long time of stability and good selectivity for NRR.…”

Mn-Doped Bi2O3 Nanosheets from a Deep Eutectic Solvent toward Enhanced Electrocatalytic N2 Reduction

“…NH 3 synthesis based on the electrochemical nitrogen reduction reaction (NRR) has recently been considered as a valuable strategy, which can be operated under ambient conditions without disastrous pollution. − However, the electrochemical NRR is severely restricted by the sluggish reaction kinetics of breaking the ultrastable NN bond and the competitive HER, resulting in a poor NH 3 yield rate and low faradaic efficiency (FE). , Consequently, it is extremely urgent to design advanced catalysts for achieving admirable NRR performance. Until now, a diversity of metallic and nonmetallic catalysts have been considered to be promising candidates toward the electrochemical NRR. − Among others, Bi-based materials are attractive catalysts for the electrochemical NRR. Particularly, Bi-based catalysts are conducive to adsorbing and activating N 2 owing to the strong interaction between Bi 6p orbitals and N 2p orbitals, which can effectively suppress the competitive HER. − As a typical Bi-based catalyst, Bi 2 O 3 demonstrates promising electroactivity for the NRR, , but the large overpotential leads to an unsatisfactory FE.…”