Open research questions in Ammonia Synthesis and Nitrogen Reduction

The lack of highly efficient ammonia production methods through electrocatalytic nitrate reduction reaction. The limited understanding of the electronic structures and reaction trends of unconventional face-centered cubic and hexagonal close-packed/face-centered cubic RuMo alloy nanoflowers.

The accumulation of NO2− on the surface of Cu-based catalysts. The need for a new electrocatalyst with enhanced NO3 RR activity and long-term durability.

Abstract Inspired by enzymatic proton-coupled electron transfer (PCET) control, introducing proton relays into catalysts' second coordination sphere accelerates proton-transfer reactions, yet this strategy remains underexplored for the catalysis of ammonia oxidation reaction (AOR).

Electrochemical N 2 -to-NH 3 conversion is attracting intense interest, yet catalysts that combine high activity, selectivity, and stability remain scarce.

However, the efficiency of e -NO 3 RR is limited by the sluggish reaction kinetics due to the high activation energy barriers, poor mass transport, and the weaker adsorption affinity of the catalyst surface.

While metal–nitrogen–carbon (M–N–C) single-atom catalysts have emerged as promising candidates for the NO 3 RR, the structure–activity relations underlying their catalytic behavior remain to be elucidated.

However, its efficiency is often limited by the slow conversion of intermediates due to spin-forbidden processes.

However, a molecular-level understanding is still lacking for the design of more efficient MOP electrocatalysts.

This review aims to invigorate research in the emerging yet underexplored field of NRR, contributing meaningfully toward sustainable development and environmental stewardship.

While 2D MXenes hold great promise as electrocatalysts for NO 3 RR, their application for ammonia production remains underexplored.

Most current efforts have focused on NO 3 RR under alkaline/neutral media with the low nitrate concentration range, while the investigation of NO 3 RR under acidic conditions in highly concentrated electrolyte is rarely reported, which ignores the strongly acidic environments in most industrial nitrate‐containing wastewaters and contradicts with the demands of actual large‐scale production.

Unlike conventional catalytic descriptors, topological surface states (TSSs) represent an orthogonal avenue for tailoring catalytic properties, while its role in NO 3 − RR remains unknown.

Investigations into the component configuration at the atomic level are still lacking.

Electrocatalytic urea synthesis is significantly limited by the low efficiency of C–N bond coupling between CO 2 and nitrite.

Unfortunately, key mechanistic insights into the heterogeneous reduction of nitrogen and its intermediates are lacking.

Although the NO 2 RR involves the transfer of multiple protons competing with the hydrogen evolution reaction (HER), the effect of the proton donor has not been investigated in heterogeneous electrocatalysis.

However, the active site requirements and reaction mechanisms of Li-assisted catalysts remain controversial.

However, NOR efficiency is fundamentally limited by the competing four-electron oxygen evolution reaction (OER) that dominates at the electrode–electrolyte interface.

15, 871, 2024), yet the microscopic origin of this promotional effect is not fully understood.

While most studies to date have focused on plasma ammonia synthesis under ambient pressure, the potential benefits of elevated pressure, such as improved thermodynamic favorability and enhanced compatibility with downstream ammonia separation technologies, remain underexplored.

Transitioning to low-carbon ammonia is vital for China’s carbon-neutrality target; however, the economic viability of deployment remains uncertain.

However, NO 3 RR is still limited by the competition from hydrogen evolution reaction (HER) and the high energy barrier in the hydrogenation step of nitrogen-containing intermediates.

However, as is the case with early-stage technologies, its full potential in decarbonization and substituting conventional infrastructure at higher manufacturing readiness levels remains unknown.

However, this conversion process remains limited by a low Faradaic efficiency (FE) and NH3 yield.

Ammonia splitting to hydrogen is a decisive route for hydrogen economy but is seriously limited by the complex device and low efficiency.