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Advisor(s)
Abstract(s)
Direct seawater electrolysis is proposed as a potential low-cost approach to
green hydrogen production, taking advantage of the vastly available seawater
and large-scale offshore renewable energy being deployed. However,
developing efficient, earth-abundant electrocatalysts that can survive under
harsh corrosive conditions for a long time is still a significant technical challenge.
Herein, the fabrication of a self-supported nickel-iron phosphosulfide
(NiFeSP) nanotube array electrode through a two-step sulfurization/phosphorization
approach is reported. The as-obtained NiFeSP nanotubes comprise
abundant NiFeS/NiFeP heterointerfaces and under-coordinated metal sites,
exhibiting outstanding activity and durability for the hydrogen and oxygen
evolution reactions (HER and OER) in simulated alkaline-seawater solution
(KOH + NaCl), with an overpotential of 380 (HER) and 260 mV (OER) at
500 mA cm-2 and outstanding durability of 1000 h. Theoretical calculations
support the observed outstanding performance, showing that the heterointerface
and under-coordinated metal sites synergistically lower the energy barrier
of the rate-determining step reactions. The NiFeSP electrode also shows good
catalytic performance for the urea oxidation reaction (UOR). By coupling UOR
with HER, the bifunctional NiFeSP electrode pair can efficiently catalyze the
overall urea-mediated alkaline-saline water electrolysis at 500 mA cm-2 under
1.938 V for 1000 h without notable performance degradation.