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

Abstract

The electrochemical urea oxidation reaction (UOR) is an alternative to electrooxidation of water for energy–saving hydrogen (H₂) 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 H₂ production.