The electrochemical reduction reaction of NO3− (NO3RR) represents a promising green technology for ammonia (NH3) synthesis. Among various electrocatalysts, Co-based materials have demonstrated considerable potential for the NO3RR. However, the NH3 production efficiency of Co-based materials is still limited due to challenges in the competitive hydrogen evolution reaction (HER) and hydrogenating oxynitride intermediates (*NOx). In this study, tungsten (W) and cobalt (Co) elements are co-incorporated to form cobalt tungstate (CoWO4) nanoparticles with dual active sites of Co2+ and W6+, which are applied to optimize the hydrogenation of NOx and decrease the HER, thereby achieving a highly efficient NO3RR to NH3. Theoretical calculations indicate that the Co sites in CoWO4 facilitate the adsorption and hydrogenation of *NOx intermediates, while W sites suppress the competitive HER. These dual active sites work synergistically to enhance NH3 production from the NO3RR. Inspired by these calculations, CoWO4 nanoparticles are synthesized using a simple ion precipitation method, with sizes ranging from 10 to 30 nm. Electrochemical performance tests demonstrate that CoWO4 nanoparticles exhibit a high faradaic efficiency of 97.8 ± 1.5% and an NH3 yield of 13.2 mg h−1 cm−2. In situ Fourier transform infrared spectroscopy characterizes the enhanced adsorption and hydrogenation behaviors of *NOx as well as a minimized HER on CoWO4, which contributes to the high efficiency and selectivity to NH3. This work introduces CoWO4 nanoparticles as an electrocatalytic material with dual active sites, contributing to the design of electrocatalysts for NH3 synthesis.
