High-Yield Electrocatalytic Nitrate Reduction via Tandem Fe-Ru Catalysts

These results were observed under controlled laboratory conditions, so real-world performance may differ.

2336.43 μg of ammonia per hour per milligram of catalyst. That is the yield achieved by a new integrated cascade catalytic system, maintaining a massive 96.03% Faradaic efficiency at a low potential of 0 V vs RHE. Most current methods fail to reach these metrics due to inefficient electron transfers.

Optimising Electrocatalytic Nitrate Reduction

**Electrocatalytic nitrate reduction** (NO₃^-RR) powered by renewables is a primary candidate for green ammonia synthesis. However, the process is notoriously difficult. Sluggish proton-coupled electron transfer often plagues the reaction, leading to unwanted byproducts rather than pure ammonia (NH₃). This study confronts these physical limitations directly by constructing a representative catalyst composed of atomically dispersed Iron (Fe) sites anchored on a Nitrogen-doped carbon matrix, encapsulating Ruthenium (Ru) nanoparticles. Why this matters is simple: Ammonia production currently accounts for significant global carbon emissions. Simultaneously, nitrate runoff pollutes water systems. Converting one problem into the solution for the other requires extreme chemical precision. The study indicates that this specific Fe-Ru configuration lowers the energy barrier significantly compared to single-metal counterparts.

Mechanistic Insights via Spectroscopy

The team utilised operando SR-FTIR spectroscopy and DFT calculations to observe the reaction dynamics. The data reveals a distinct electron transfer from the Fe atom to the Ru particle. This shift is functional, not merely structural. It enhances the affinity of Fe sites for nitrogen oxide species, effectively trapping the pollutant. Simultaneously, it enriches hydrogen coverage on the Ru sites. This creates a highly efficient hydrogenation environment. The Ru acts as a dedicated hydrogen reservoir, accelerating the steps required to turn nitrate into ammonia. This sustains a steady generation-consumption cycle of active hydrogen (*H). These findings provide fundamental insights for designing durable, energy-efficient systems for wastewater treatment and electrosynthesis. The high selectivity suggests that tandem structures are the correct path forward for industrial scaling.