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.
Deeply exploring the real reaction sites in composite catalysts for electrocatalytic reaction has profound significance, especially in low energy cost hydrogen production coupling with urea electrocatalytic oxidation (UOR). Herein we...
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