Ternary Synergy in Layered Double Hydroxides for Efficient and Stable Nitrate Reduction

Nitrate pollution from agricultural runoff and industrial discharge poses severe environmental and health risks, necessitating sustainable remediation. Electrocatalytic nitrate reduction reaction (NO₃RR) offers a promising solution by converting nitrate to ammonia, where catalysts with high activity and selectivity are needed. Here, it is reported that layered double hydroxides (LDHs) can achieve highly efficient NO₃RR performance through composition engineering and in situ reconstruction. It is shown that a ternary CuZnFe LDH catalyst can leverage synergistic effects and controlled surface reconstruction for highly efficient and stable reduction of nitrate to ammonia. During NO₃RR, copper compound is reduced to a metallic state for enhanced activity, reconstructed iron oxide stabilizes the structure and improves the activity, and zinc is selectively leached to expose active sites. In situ ATR-FTIR spectroscopy reveals that metallic copper initiates nitrate-to-nitrite conversion, while iron oxide drives ammonia formation. As a result, the catalyst achieves a Faraday efficiency of 95% for ammonia, an ammonia yield of 51 mg h⁻¹ cm⁻², a current density of 0.64 A cm⁻² at −0.9 V vs. RHE, and high stability. The findings provide an insightful understanding on the NO₃RR mechanism, novel strategies for the design of tandem catalysts through in situ reconstruction and composition engineering for advanced nitrate remediation.