CoWO nanoparticles with dual active sites for highly efficient ammonia synthesis.

The electrochemical reduction reaction of NO (NORR) represents a promising green technology for ammonia (NH) synthesis. Among various electrocatalysts, Co-based materials have demonstrated considerable potential for the NORR. However, the NH production efficiency of Co-based materials is still limited due to challenges in the competitive hydrogen evolution reaction (HER) and hydrogenating oxynitride intermediates (*NO). In this study, tungsten (W) and cobalt (Co) elements are co-incorporated to form cobalt tungstate (CoWO) nanoparticles with dual active sites of Co and W, which are applied to optimize the hydrogenation of NO and decrease the HER, thereby achieving a highly efficient NORR to NH. Theoretical calculations indicate that the Co sites in CoWO facilitate the adsorption and hydrogenation of *NO intermediates, while W sites suppress the competitive HER. These dual active sites work synergistically to enhance NH production from the NORR. Inspired by these calculations, CoWO nanoparticles are synthesized using a simple ion precipitation method, with sizes ranging from 10 to 30 nm. Electrochemical performance tests demonstrate that CoWO nanoparticles exhibit a high faradaic efficiency of 97.8 ± 1.5% and an NH yield of 13.2 mg h cm. Fourier transform infrared spectroscopy characterizes the enhanced adsorption and hydrogenation behaviors of *NO as well as a minimized HER on CoWO, which contributes to the high efficiency and selectivity to NH. This work introduces CoWO nanoparticles as an electrocatalytic material with dual active sites, contributing to the design of electrocatalysts for NH synthesis.