Dual atom Cu–Fe ensemble sites for enhanced efficiency of green ammonia production from the tandem electrochemical nitrate reduction process

Abstract

The electrochemical nitrate reduction reaction (NO₃RR) is a promising strategy for sustainable ammonia production and nitrate remediation in aqueous systems. Designing efficient electrocatalysts for NO₃RR has attracted significant attention, with single-atom catalysts (SACs) offering advantages like high atomic utilization and well-defined active sites. However, single-atom catalysts (SACs) suffer from limited functionality for multi-step transformations. Herein, we report a Cu–Fe dual-atom catalyst anchored on nitrogen-doped carbon (Cu–Fe DAC/NC), designed to enable bifunctional catalysis for efficient NO₃RR. Comprehensive characterization studies confirm atomically dispersed Cu and Fe ensemble sites with strong N coordination, promoting electronic interaction and structural stability. Electrochemical tests reveal that the Cu–Fe DAC/NC showed a high faradaic efficiency of 94.3% and an NH₃ production rate of 6.0 mg cm⁻² h⁻¹ at −0.53 V (vs. RHE), outperforming individual SACs. Mechanistic insights obtained via nitrate/nitrite control experiments and DFT calculations revealed a tandem mechanism: Cu sites initiate NO₃⁻ activation, while Fe sites facilitate NO₂⁻ hydrogenation. This tandem mechanistic process enables high selectivity and activity across the full reaction pathway. Our work highlights the potential of dual-atom site engineering to enable cooperative catalysis beyond the limitations of SACs, offering new design strategies for electrocatalysts in multi-electron transformations of nitrogen-containing compounds.