A comprehensive review on electrochemical green ammonia synthesis: From conventional to distinctive strategies for efficient nitrogen fixation

Abstract

Ammonia (NH3) is an excellent transition fuel of green hydrogen and a future contender in the energy market. However, industrial NH3 production currently depends on the unsustainable and energy-intensive Haber–Bosch process. Hence, developing a viable and efficient method to produce NH3 economically has become a new challenge for researchers as its demand surges with each passing decade. Ammonia production from renewable energy sources can power the globe without emitting carbon. The electrochemical method of NH3 has emerged as an appealing strategy for sustainable NH3 production under mild conditions. However, this approach presents several challenges related to activating the highly stable N≡N bond, choice of electrolytes, proton source, etc. This study explores electrochemical methods with distinctive approaches that have been reported, which include redox-mediated processes, lithium cycling electrification, integrated plasma technology, phosphonium proton shuttling, and more. A comprehensive analysis of the underlying principles, experimental parameters, challenges, and potential applications are discussed for each method. It also assesses the recent electrocatalyst advancements employed for effective N2 fixation and their corresponding electrocatalytic performance. Finally, it emphasises the ongoing research efforts to overcome barriers and enable the widespread adoption of renewable grid energy systems for powering N2 gas electrolysis in green NH3 production.