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 easily overoxidize urea into the secondary contaminant NO , 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 to regulate its activity and selectivity. Smaller cations of Li were discovered to increase the Faradaic efficiency (FE) of the innocuous N product from the standard value of ~15 % to 45 %, while decreasing the FEs of the over-oxidized NO product 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 forms 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 N pathway. This work emphasizes the tuning of the interactions within the electrode-electrolyte interface for enhancing the efficiency and sustainability of electrocatalytic processes.