SummaryElectrochemical reduction of nitrite (NO2−) can satisfy the necessity for NO2−contaminant removal and deliver a sustainable pathway for ammonia (NH3) generation. Its practical application yet requires highly efficient electrocatalysts to boost NH3yield and Faradaic efficiency (FE). In this study, CoP nanoparticle-decorated TiO2nanoribbon array on Ti plate (CoP@TiO2/TP) is verified as a high-efficiency electrocatalyst for the selective reduction of NO2−to NH3. When measured in 0.1 M NaOH with NO2−, the freestanding CoP@TiO2/TP electrode delivers a large NH3yield of 849.57 μmol h−1cm−2and a high FE of 97.01% with good stability. Remarkably, the subsequently fabricated Zn–NO2−battery achieves a high power density of 1.24 mW cm−2while delivering a NH3yield of 714.40 μg h−1cm−2.