Fabrication of a Novel Cu Based Conjugated Coordination Polymer for Effective Electroreduction of Nitrate to Ammonia and Zn–Nitrate Batteries

Abstract

Nitrate electroreduction to ammonia (NRA) offers a sustainable pathway to convert widespread nitrate pollutants into high-value NH3 under ambient conditions. However, the complex electron/proton transfer process in NRA is often hindered by competing hydrogen evolution reactions, leading to low ammonia selectivity and faradic efficiency. Conjugated coordination polymers (CCPs), characterized by high electronic conductivity, abundant metal active sites, and tunable structures, emerge as promising catalysts for energy-related applications. Herein, the synthesis of two CCPs, Cu3(HITP)2/CF (Cu–N4) and Cu3(HHTP)2/CF (Cu–O4), is reported featuring a unique “pine-like” morphology grown on copper foam substrates. This design maximizes active site exposure, while Cu–N4 coordination optimizes the Cu d-band center, enhances NO3− adsorption, and lowers the energy barrier for the rate-determining step in NRA. As a result, Cu3(HITP)2/CF achieves a remarkable ammonia yield of 19.9 mg h−1 cm−2 with a faradic efficiency of 87.87%, outperforming Cu3(HHTP)2/CF. Furthermore, a Zn–NO3− battery using Cu3(HITP)2/CF delivers a power density of 7.18 mW cm−2 and excellent cycling stability over 110 cycles. This work underscores the potential of tuning CCPs coordination environments and morphologies to enhance NRA performance.