Pathway Manipulation via Ni, Co, and V Ternary Synergism to Realize High Efficiency for Urea Electrocatalytic Oxidation

Ni is the one of most efficient active sites for triggering urea electrooxidation (UOR); however, 'it is hard to achieve higher activity and stability with only the Ni site. To address issues such as dehydrogenation, C-N bond breakage, and catalyst poisoning caused by carbonaceous fragments simultaneously, manipulating a pathway via building a multi-synergistic system is essential. Therefore, we constructed a Co, V co-doped NiS2 ternary collaborative system to achieve energy-saving urea electrooxidation with an emphasis on catalytic mechanism investigation. The optimal ternary catalyst exhibited good urea electrooxidation activity (77 mA cm(-2) at 1.5 V vs RHE), stability, and hydrogen production (143 L min(-1) g(cat)(-1) at 1.8 V vs RHE). Based on X-ray photoelectron spectroscopy, in situ electrochemical Raman spectroscopy, an in situ electrochemical mass spectrometry isotope tracing experiment, and the density functional theory study, the roles of Ni, Co, and V elements were clearly revealed. The extended superexchange interaction not only enhanced the electron transmission capacity between Ni and S but also accelerated the electron transfer between urea and the catalyst. Anti-CO poisoning experiments indicated that the existence of Co can accelerate the oxidation of carbonaceous intermediate products and improve the catalyst stability. More importantly, we found that N-2 was formed through the urea intermolecular N-N coupling process under the catalysis of metal sulfide. The strategy and mechanism proposed herein give a deeper understanding of UOR catalyzed by metal sulfides.

Automated summary

This study achieved energy-saving urea electrooxidation by constructing a Co, V co-doped NiS2 ternary collaborative system, improving both activity and stability. Through a series of experiments and theoretical studies, the roles of Ni, Co, and V elements in the catalytic process were clearly revealed.