Integrated Three-in-one to Boost Nitrate Electroreduction to Ammonia Utilizing a 1D Mesoporous Carbon Cascade Nanoreactor

The electrochemical reduction of nitrate (NO 3 – ) offers a promising waste-to-value strategy for synthesizing ammonia (NH 3 ), yet it involves a complex multi-interface system with several stages such as mass transport, species enrichment, and interfacial transformation. This complexity necessitates catalysts with diverse structural characteristics across multiple temporal and spatial scales. Herein, a three-in-one nanoreactor system is designed with 1D geometry, open mesochannels, and synergistic active sites for optimized NH 3 synthesis. Guided by finite element simulations, a 1D mesoporous carbon carrier is engineered to create a distinctive microenvironment that enhances NO 3 – transfer and adsorption while confining reaction intermediates. Meanwhile, iron single atomic sites (Fe–N 4 SAs) and iron nanoclusters (Fe 4 NCs) are embedded in situ into the carbon carrier, yielding an efficient cascade nanoreactor. This design demonstrates large Faraday efficiencies, rapid NO 3 – removal rates, and impressive NH 3 yield rates under both neutral and alkaline conditions. Detailed in situ experimental results and theoretical analysis reveal that Fe–N 4 SAs and Fe 4 NCs can adapt their electronic structures in tandem, allowing the Fe–N 4 SAs to effectively reduce NO 3 – and Fe 4 NCs to oxidize H 2 O. As a demonstration, the assembled Zn–NO 3 – battery achieves a power density of 20.12 mW cm –2 coupled with excellent rechargeability.