Linking CO to Urea Production from CO2 and NO3 -/NO2 - Co-Electrolysis on Transition Metals

Abstract

Electrochemical reduction of CO2 (CO2ER) has the potential to advance carbon neutrality and renewable energy storage. Advanced CO2ER catalysts can selectively produce a wide array of products. Their importance is amplified when coreducing CO2 with nitrate/nitrite ions (NO3-/NO2-) to generate organic compounds containing C-N bonds, enhancing product diversity and value. Some transition metals effectively catalyze the coreduction of CO2 and NO3-/NO2- to yield urea. However, a disparity exists between the experimental observations that underscore the significance of CO production in urea synthesis and the theoretical perspectives that dismiss the role of CO in C-N bond creation. To reconcile this disparity, we utilized density functional theory combined with a constant electrode potential model to investigate four facile CO2 + *N-1 (the intermediates from NO3-/NO2- reduction to NH3) couplings & horbar;representing the primary C-N formation pathways on a range of transition metal surfaces. Our comprehensive study elucidates the relationships among C-N coupling barriers, *N-1, and CO adsorption energies. Notably, we found that while CO is not involved in C-N formation, a catalyst's proficiency in generating CO from CO2ER is indicative of its reduced adsorption strength. This result indicates a heightened reactivity in forming C-N bonds via the CO2 + *N-1 couplings. Our theoretical exploration adeptly bridges the discrepancies observed between earlier experimental and theoretical studies.