Regulating the Innocuity of Urea Electro‐Oxidation via Cation‐mediated Adsorption

Urea electrolysis is an emerging technology that bridges efficient wastewater treatment and hydrogen production with lower electricity costs. However, conventional Ni-based catalysts could facilely over-oxidize urea into the secondary contaminant of NOx-, and enhancing the innocuity of urea electrolysis remains a grand challenge to be achieved. Herein, we tailored the electrode-electrolyte interface of an unconventional cation effect on the anodic oxidation of urea for regulating its activity and selectivity. Smaller cations of Li+ were discovered to increase the Faradaic efficiency (FE) of the innocuous N2 product from the standard value of ~15% to 44%, while decreasing the FEs of the over-oxidized NOx- products from ~80% to 46%, pointing to a more sustainable process. The kinetic and computational analysis revealed the dominant residence of cations on the outer Helmholtz layer, which form the interactions with the surface adsorbates. The Li+ hydration shells and rigid hydrogen bonding network interact strongly with the adsorbed urea to decrease its adsorption energy and subjection to C-N cleavage, thereby directing it toward the N2 pathway. This work emphasizes the tuning of the interactions within the electrode-electrolyte interface for enhancing the efficiency and sustainability of electrocatalytic processes.