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

Abstract

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 gcat–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 N2 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.