Low-Coordination Rhodium Catalysts for an Efficient Electrochemical Nitrate Reduction to Ammonia

Abstract

Ammonia is an essential bulk chemical and the main component of fertilizers. In addition, the use of ammonia (NH3) as an energy carrier and hydrogen storage material has continuously surged. Electrochemical nitrate reduction is a low-carbon, environment-friendly, and efficient method of ammonia synthesis, which has attracted extensive attention in recent years; however, the overpotential needed to produce NH3 with most catalysts is still too large. In this work, we rationally designed rhodium nanoflowers (Rh NFs) composed of ultrathin nanosheets and explored their performance for the electrocatalytic nitrate reduction to ammonia (NITRR). With a high faradic efficiency of 95% at 0.2 V vs reversible hydrogen electrode (RHE) for ammonia production, the overpotential required for the NH3 formation on an Rh NF catalyst is much lower than on most previously reported catalysts. X-ray absorption spectroscopy (XAS) analysis shows that there are low-coordination atoms in the Rh NF catalyst, which can promote the adsorption of NO3 – ions and stabilize intermediates as revealed by the density functional theory (DFT) calculation, resulting in efficient NITRR performance.

Electrochemical Co-Production of Ammonia and Biodegradable Polymer Monomer Glycolic Acid via the Co-Electrolysis of Nitrate Wastewater and Waste Plastic

“…Specifically, K 15 NO 3 as a reactant was electrolyzed for 2 h at −0.25 V vs RHE, and the collected electrolyte was analyzed by 1 H NMR. As shown in Figure 4c, the double peak of 15 NH 4 + is observable in the 1 H NMR spectrum of K 15 NO 3 as a reactant, which is different from the triple peak of . Further, the converted 15 NH 3 −N concentration is quantitatively calculated by the calibration curve (maleic acid as an external standard, Figure S9a, b).…”

“…For the waste upcycling coupled electrolysis system, the construction of efficient cathode and anode electrocatalysts is essential. In recent years, various metals, metal alloys, and metal compounds (such as Fe, Fe-V 2 O 5 , Co, Cu/Cu 2 O, RuO 2 , Cu, Rh, PdBi, CuCoSP, CuPd) have been developed as electrocatalysts for NO 3 RR. ,,− Among these materials, Co-based materials have become a competitive catalyst due to their high NH 3 selectivity. For example, ultrathin CoO x nanosheets are developed and applied in the NO 3 RR process, demonstrating high ammonia yield (82.4 ± 4.8 mg h –1 mg cat –1 ) and Faradic efficiency (FE, 93.4 ± 3.8%) .…”

Sustainable Production and In-place Utilization of a Liquid Nitrogenous Fertilizer

“…6,22 The process of the electrochemical nitrate reduction reaction (NO 3 RR) can be summarized as the deoxidation and hydrogenation of nitrogencontaining intermediates, involving the transfer of eight electrons and nine protons. 28,30,31 There are many stable intermediates with various valence states, including NO 2 , NO, N 2 O, N 2 and NH 2 OH, which can escape from the catalyst surface as products. Although the thermodynamic equilibrium potential of each intermediate varies considerably, many intermediates may coexist in the actual catalytic process due to the speci c kinetic processes and the differences in their adsorption energy.…”

“…Noble metal-based catalysts with empty d-orbitals have been considered state-of-the-art electrocatalysts for the NO 3 RR due to the role of d-orbital electrons in enhancing charge injection of the lowest vacancy molecular orbital of nitrate. Luo et al30 designed rhodium nano owers as NO 3 RR electrocatalysts, in which the low-coordination Rh atoms facilitated the adsorption of nitrate ions and stabilized the…”

A strong metal–support interaction strategy for enhanced binder-free electrocatalytic nitrate reduction

“…[12][13][14][15] Based on previous research studies, bimetallic-based catalysts containing noble metals (e.g., Pt-Ru, Pd-Cu, Pd-Sn) are considered to be excellent catalysts for the electrocatalytic NO 3 RR. [16][17][18][19][20] However, in order to reduce the cost and enhance the properties, numerous non-precious metal catalysts have been studied. [21][22][23][24][25] Fe-based electrocatalysts have stood out in replacing traditional noble metals due to their low cost, high reduction capacity, easy availability and recyclability.…”