Breaking Linear Scaling Relation Limitations on a Dual-driven Single-atom Copper/Tungsten Oxide Catalyst for Ammonia Synthesis.

Electrocatalytic reduction of nitrate (NO3-, NO3RR) on single-atom copper catalysts (Cu-SACs) offers a sustainable approach to ammonia (NH3) synthesis using NO3- pollutants as feedstocks. Nevertheless, this process suffers from inferior NO3RR kinetics and nitrite accumulation owing to the linear scaling relation limitations for SACs. To break these limitations, a single-atom Cu-bearing tungsten oxide catalyst (Cu1/WO3) was developed, which mediated a unique dual-driven NO3RR process. Specifically, WO3 dissociated water molecules and supplied the Cu1 site with ample protons, while the Cu1 site in an electron-deficient state converted NO3- to NH3 efficiently. The Cu1/WO3 delivered an impressive NH3 production rate of 1274.4 mgN h-1 gCu-1, a NH3 selectivity of 99.2%, and a Faradaic efficiency of 93.7% at -0.60 V, surpassing most reported catalysts. Furthermore, an integrated continuous-flow system consisting of NO3RR cell and vacuum-driven membrane separator was developed for NH3 synthesis from nitrate-contaminated water. Fed with the Yangtze River water containing ~22.5 mg L-1 of NO3--N, this system realized an NH3 production rate of 325.9 mgN h-1 gCu-1 and a collection efficiency of 98.3% at energy consumption of 17.11 kwh gN-1. This study provides a new dual-driven concept for catalyst design and establishes a foundation for sustainable NH3 synthesis from waste.