Bowen Li, Yinlong Zhu*, Wanlin Guo. 

Inorganic Chemistry Frontiers(2023)

Abstract: 

World ammonia production is reaching 235 million tons in 2019, and roughly 88% of NH₃ produced goes into agriculture section as fertilizers. Industrial ammonia production relies on the Haber-Bosch process, which is highly energy demanding and results in high CO₂ emission. More than 1% of global energy generation was required to power this Haber-Bosch process. While sustainable development has become a general consensus across the globe, there have been enormous research interests toward possible modification or replacement of the Haber-Bosch process, aiming to reduce the environmental impact of NH₃ production. With the successful commercialization of various renewable source powered electricity generation techniques, electrochemical reduction of nitrogen containing chemicals (including N₂, NO₃^-, NO₂^- and NO) to produce NH₃ under ambient conditions has emerged as a potential green alternative to the Haber-Bosch process. This technique utilizes renewable electricity to achieve small-scale, on-site and on-demand ammonia production, serving as a critical contribution to overall carbon neutral economy. Design and synthesis of novel catalysts with high NH₃ production rate and selectivity is the key challenge in determining the economic feasibility of this electrochemical NH₃ production. In view of the rapid and fruitful development of metal oxides as promising electrocatalysts toward NH₃ formation, this review summarizes different types of metal oxides used for electrochemical N₂ reduction reaction and electrochemical NO_x reduction reaction, together with design strategies to enhance their catalytic performance. As a concluding remark, our thoughts are given on the critical challenges in this field, suggesting possible future research directions to accomplish industrialization for electrosynthesis of NH₃.

Link: https://pubs.rsc.org/en/content/articlelanding/2023/QI/D3QI01448G