Rigorous Assessment of Cl- -Based Anolytes on Electrochemical Ammonia Synthesis

Preventing Nitrite Desorption via Switching Hydrogenation Position: A Dual-Site Approach for Selective Nitrate Reduction to Ammonia

The electrochemical nitrate reduction reaction (NO3RR), which converts harmful nitrates into valuable ammonia (NH3) with zero carbon emission, is one of the most promising alternatives to the Haber-Bosch process. However, the NO3RR process is complex and involves multiple proton-coupled electron transfers that generate intermediates or byproducts, such as NO2 -, resulting in low ammonia yields and faradaic efficiency (FE). Herein, by constructing a FeCu bimetallic catalyst (FeCu-NC), the hydrogenation position of *NO3 is switched at the FeCu dual-atom site, preventing the desorption of *NO2 intermediate. Furthermore, electron transfer from Cu to Fe sites mimics the electron flow direction in natural nitrite reductase enzymes and accelerates the reduction of *NO2 to NH3, achieving efficient conversion of NO3 - to NH3. A 24-hour electrocatalytic experiment with FeCu-NC demonstrates negligible NO2 - formation throughout the NO3RR process, with an ammonia production rate of 6.13 mg h-1 mgcat -1 and an impressive FE of 95%, which are remarkably superior in comparison to most of the NO3RR electrocatalysts. This work opens new avenues for the fundamental understanding of catalytic mechanisms and the development of next-generation catalysts for sustainable ammonia production.

NH3 Electrosynthesis from N2 Molecules: Progresses, Challenges, and Future Perspectives

Green ammonia (NH3), made by using renewable electricity to split nearly limitless nitrogen (N2) molecules, is a vital platform molecule and an ideal fuel to drive the sustainable development of human society without carbon dioxide emission. The NH3 electrosynthesis field currently faces the dilemma of low yield rate and efficiency; however, decoupling the overlapping issues of this area and providing guidelines for its development directions are not trivial because it involves complex reaction process and multidisciplinary entries (for example, electrochemistry, catalysis, interfaces, processes, etc.). In this Perspective, we introduce a classification scheme for NH3 electrosynthesis based on the reaction process, namely, direct (N2 reduction reaction) and indirect electrosynthesis (Li-mediated/plasma-enabled NH3 electrosynthesis). This categorization allows us to finely decouple the complicated reaction pathways and identify the specific rate-determining steps/bottleneck issues for each synthesis approach such as N2 activation, H2 evolution side reaction, solid-electrolyte interphase engineering, plasma process, etc. We then present a detailed overview of the latest progresses on solving these core issues in terms of the whole electrochemical system covering the electrocatalysts, electrodes, electrolytes, electrolyzers, etc. Finally, we discuss the research focuses and the promising strategies for the development of NH3 electrosynthesis in the future with a multiscale perspective of atomistic mechanisms, nanoscale electrocatalysts, microscale electrodes/interfaces, and macroscale electrolyzers/processes. It is expected that this Perspective will provide the readers with an in-depth understanding of the bottleneck issues and insightful guidance on designing the efficient NH3 electrosynthesis systems.

Refining the Spectroscopic Detection Technique: A Pivot in the Electrochemical Ammonia Synthesis

Ammonia has been recognized as the future fuel because of its immense advantages over liquid hydrogen. The research trend nowadays is mostly inclined toward the electrochemical ammonia synthesis since it offers a sustainable method of green ammonia production. The indophenol blue method is one of the largely used colorimetric techniques to detect ammonia spectroscopically but lacks a proper experimental protocol. The unresolved speculations related to this method concerning stability of dye, sequence of mixing of reagents, importance of pH in the dye formation, or sensitivity of the method to interferants need vigorous experimental verification and a legitimate protocol has to be set up for a reliable and reproducible data. This work thus aims to unveil the artefacts of this method and explore the mechanisms involved such that it becomes easy for a newcomer as well as existing researchers in the field to understand the requirement of rigorous optimizations in this technique.