Directed Urea-to-Nitrite Electrooxidation via Tuning Intermediate Adsorption on Co, Ge Co-Doped Ni Sites

The electrochemical urea oxidation reaction (UOR) is an alternative to electrooxidation of water for energy-saving hydrogen (H-2) production. To maximize this purpose, design of catalysts for selective urea-to-nitrite (NO2-) electrooxidation with increased electron transfer and high current is practically important. Herein, a cobalt, germanium (Co, Ge) co-doped nickel (Ni) oxyhydroxide catalyst is reported first time that directs urea-to-NO2- conversion with a significant Faradaic efficiency of 84.9% at 1.4 V versus reversible hydrogen electrode and significantly boosts UOR activity to 448.0 mA cm(-2). Importantly, this performance is greater than for most reported Ni-based catalysts. Based on judiciously combined synchrotron-based measurement, in situ spectroscopy and density functional theoretical computation, significantly boosted urea-to-NO2- production results from Co, Ge co-doping is demonstrated that optimizes electronic structure of Ni sites in which urea adsorption is altered as NO-terminal configuration to facilitate C-N cleavage for *NH formation, and thereby expedites pathway for urea to NO2- conversion. Findings highlight the importance of tuning intermediate adsorption behavior for design of high-performance UOR electrocatalysts, and will be of practical benefit to a range of researchers and manufacturers in replacing conventional water electrooxidation with UOR for energy-saving H-2 production.

Automated summary

A cobalt, germanium co-doped nickel oxyhydroxide catalyst is reported that effectively converts urea to nitrite and enhances electron transfer and current. Through synchrotron-based measurement, in situ spectroscopy and density functional theoretical computation, it is demonstrated that the co-doping of cobalt and germanium optimizes the electronic structure of nickel sites, promoting the cleavage of the C-N bond and conversion of urea to nitrite.