Carbon dioxide and nitrate co-electroreduction to urea on CuOxZnOy

Urea is a commonly used nitrogen fertiliser synthesised from ammonia and carbon dioxide using thermal catalysis. This process results in high carbon dioxide emissions associated with the required amounts of ammonia. Electrocatalysis provides an alternative method to urea production with reduced carbon emissions while utilising waste products like nitrate. This manuscript reports on urea synthesis from the electroreduction of nitrate and carbon dioxide using CuO x ZnO y electrodes under mild conditions. Catalysts with different ratios of CuO and ZnO, synthesised via flame spray pyrolysis, were explored for the reaction. The results revealed that all the CuO x ZnO y electrocatalyst compositions produce urea, but the efficiency strongly depends on the metal ratio composition of the catalysts. The CuO 50 ZnO 50 composition had the best performance in terms of selectivity (41% at −0.8 V vs RHE) and activity (0.27 mA/cm 2 at −0.8 V vs RHE) towards urea production. Thus, this material is one of the most efficient electrocatalysts for urea production reported so far. This study systematically evaluates bimetallic catalysts with varying compositions for urea synthesis from carbon dioxide and nitrate. The simultaneous electroreduction of carbon dioxide and nitrate is a promising and environmentally benign route to urea production, but achieving high selectivity for urea electrosynthesis via this route remains challenging. Here, CuO x ZnO y electrodes are shown to enable the efficient and selective production of urea under mild conditions, with the efficiency found to strongly depend on the metal ratio within the catalyst composition.