Most catalysts are metal‐based, and metal‐free catalysts with high nitrate‐to‐ammonia conversion activity are rarely reported.

The gap

Consensus across the literature

Supporting evidence — 3 representative gaps

• Direct Synthesis of Ammonia from Nitrate on Amorphous Graphene with Near 100% Efficiency (2023) · doi

  Most catalysts are metal‐based, and metal‐free catalysts with high nitrate‐to‐ammonia conversion activity are rarely reported.

  Keywords: catalysts metal based free high nitrate ammonia conversion activity rarely reported
• Insights into Electrocatalytic Nitrate Reduction to Ammonia via Cu-Based Bimetallic Catalysts (2023) · doi

  However, few studies have focused on horizontal comparison of CuNi, CuCo, and CuFe (abbreviated as CuM) bimetallic catalysts in electrocatalytic NO 3 – RR for ammonia synthesis.

  Keywords: focused horizontal comparison cuni cuco cufe abbreviated bimetallic catalysts electrocatalytic ammonia synthesis
• Cu-based catalysts for electrocatalytic nitrate reduction to ammonia: fundamentals and recent advances (2024) · doi

  Electrocatalytic ammonia production from nitrate (NO3RR) is promising and highly attractive due to its ambient reaction condition, low energy consumption, and zero CO2 emission. This review summarized the recent progress in elucidating the mechanism of NO3RR, state-of-the-art Cu-based catalysts for NO3RR, corresponding analysis methods for product detection, practical applications and economic analysis conducted to date. In recent years, significant attempts have been made by researchers to design and develop efficient and low-cost cata- lysts for this reaction. Cu-based catalysts certainly show out- standing kinetics along with selectivity towards ammonia synthesis. Most current research works mainly focus on higher FE and smaller overpotentials, aiming to improve ammonia yield and ammonia selectivity. Among them, nanomaterials with finite structures expose more active sites through a larger specific surface area, which greatly enhances the activity of the material. Also, great achievements have been made in revealing the in-depth mechanisms of NO3RR recently. On one hand, theoretical calculations give insights into the reaction pathways and rationalize a series of experimental observations. More- over, the activity and selectivity trends of different catalysts can be simulated and summarized, providing guidance for screen- ing and designing efficient catalysts. On the other hand, the in situ characterization methods widespread utilization of enables direct experimental observation during real-time reac- tions, providing a powerful means for unveiling the reaction intermediates and active species of the electrode surface. Although the great potential for electrochemical ammonia production via nitrate reduction has been proven, it is still far from the real-environment application and has some chal- lenges that need to be explored and solved. First, as a signifi- cant concern in the industry, the long-term stability of Cu- based catalysts during NO3RR should be considerably improved. Although many reported Cu-based catalysts could reach a high FE of over 90%, the problems of corrosion and dissolution still exist especially in acidic environments, leading to inferior stability. Thus, future research and development efforts should focus on optimizing the stability of copper-based catalysts. This could be achieved through various strategies, such as the use of support materials to prevent the sintering of copper particles, the incorporation of stabilizing agents to inhibit the leaching of copper ions, and the modification of the catalyst preparation method to control the oxidation state of copper. For example, it has been reported that the single-atom Cu catalysts are more likely to present appreciable stability due to the strong interactions between Cu atoms and corresponding coordination atoms.104 Second, the conventional electrode fabrication method using polymeric binders (mostly Nafion) to fix the catalyst on the electrode surface would result i

  Keywords: catalysts ammonia based reaction stability copper selectivity surface electrode production nitrate summarized recent state corresponding