To restore the natural nitrogen cycle (N-cycle), artificial N-cycle electrocatalysis with flexibility, sustainability, and compatibility can convert intermittent renewable energy (e.g., wind) to harmful or value-added chemicals with minimal carbon emissions. The background of such N-cycles, such as nitrogen fixation, ammonia oxidation, and nitrate reduction, is briefly introduced here. The discussion of emerging nanostructures in various conversion reactions is focused on the architecture/compositional design, electrochemical performances, reaction mechanisms, and instructive tests. Energy device advancements for achieving more functions as well as <i>in situ</i>/<i>operando</i> characterizations toward understanding key steps are also highlighted. Furthermore, some recently proposed reactions as well as less discussed C–N coupling reactions are also summarized. We classify inorganic nitrogen sources that convert to each other under an applied voltage into three types, namely, abundant nitrogen, toxic nitrate (nitrite), and nitrogen oxides, and useful compounds such as ammonia, hydrazine, and hydroxylamine, with the goal of providing more critical insights into strategies to facilitate the development of our circular nitrogen economy. 

https://www.sciopen.com/article_pdf/1531201054523838466.pdf

Recent advances in nanostructured heterogeneous catalysts for N-cycle electrocatalysis

Electrochemical N2 fixation represents a promising strategy toward sustainable NH3 synthesis, whereas the rational design of high-performance catalysts for the nitrogen reduction reaction (NRR) is urgently required but remains challenging. Herein, a novel hexagonal BN quantum dots (BNQDs) decorated Nb2 CTx -MXene (BNQDs@Nb2 CTx ) is explored as an efficient NRR catalyst. BNQDs@Nb2 CTx presents the optimum NRR activity with an NH3 yield rate of 66.3 µg h-1 mg-1 (-0.4 V) and a Faradaic efficiency of 16.7% (-0.3 V), outperforming most of the state-of-the-art NRR catalysts, together with an excellent stability. Theoretical calculations revealed that the synergistic interplay of BNQDs and Nb2 CTx enabled the creation of unique interfacial B sites serving as NRR catalytic centers capable of enhancing the N2 activation, lowering the reaction energy barrier and impeding the H2 evolution.

Synergistic Enhancement of Electrocatalytic Nitrogen Reduction Over Boron Nitride Quantum Dots Decorated Nb2CTx-MXene

Electrochemical N2 fixation through nitrogen reduction reaction (NRR) is a promising way for sustainable NH3 synthesis, while exploring high-performing NRR catalysts lies at the heart of attaining high-efficiency NRR electrocatalysis....

Amorphization engineered VSe2-x nanosheets with abundant Se-vacancies for enhanced N2 electroreduction

Electrocatalytic dinitrogen fixation holds great promise as a sustainable technology for future NH3 synthesis, and developing electrocatalysts for the nitrogen reduction reaction (NRR) with high activity and selectivity is highly desirable yet challenging. Herein, we reported that interface electronically coupled Sb/Nb2CTx could be a highly efficient NRR catalyst which delivered an NH3 yield of 49.8 μg h−1 mg−1 with faradaic efficiencies as high as 27.3%, representing the highest NRR selectivity achieved in MXene-based catalysts. Density functional theory calculations revealed that the coupling of Sb and Nb2CTx could generate an electron-rich interface enabling the downshift of the p-band center of interfacial Sb atoms, which served as main active sites to promote the N2 activation and hydrogenation while restricting the competing hydrogen evolution.

Constructing an electron-rich interface over an Sb/Nb2CTx–MXene heterojunction for enhanced electrocatalytic nitrogen reduction

Electrocatalytic nitrogen reduction reaction (NRR) is a promising approach for renewable NH3 production, while developing the NRR electrocatalysis systems with both high activity and selectivity remains a significant challenge. Herein, we combine catalyst and electrolyte engineering to achieve a high-efficiency NRR enabled by a Se-vacancy-rich WSe2-x catalyst in water-in-salt electrolyte (WISE). Extensive characterizations, theoretical calculations, and in situ X-ray photoelectron/Raman spectroscopy reveal that WISE ensures suppressed H2 evolution, improved N2 affinity on the catalyst surface, as well as an enhanced π-back-donation ability of active sites, thereby promoting both activity and selectivity for the NRR. As a result, an excellent faradaic efficiency of 62.5% and NH3 yield of 181.3 μg h-1 mg-1 is achieved with WSe2-x in 12 m LiClO4, which is among the highest NRR performances reported to date.

Yaojing Luo

Papers

Amorphization engineered VSe2-x nanosheets with abundant Se-vacancies for enhanced N2 electroreduction

Constructing an electron-rich interface over an Sb/Nb2CTx–MXene heterojunction for enhanced electrocatalytic nitrogen reduction

High-Efficiency N2 Electroreduction Enabled by Se-Vacancy-Rich WSe2-x in Water-in-Salt Electrolytes.

Sulfur-deficient Bi2S3−x synergistically coupling Ti3C2Tx-MXene for boosting electrocatalytic N2 reduction

B-doped MoS2 for nitrate electroreduction to ammonia.