The
intervening barrier to produce hydrogen from water is the frustratingly
slow kinetics of the water splitting reaction. In addition, insufficient
understanding of the key obstacle of the oxygen evolution reaction
(OER) is an obstruction to perceptive design of efficient OER electrocatalysts.
In this research, we present synthesis, characterization, and electrochemical
evaluation of nickel oxide/nickel sulfide (NiO/NiS) heterostructures
and its counterparts nickel oxide (NiO) and nickel sulfide (NiS) as
low-cost electrocatalysts for electrochemical water splitting. These
electrocatalysts have been characterized using powder X-ray diffraction
(XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning
electron microscopy (SEM). The NiO/NiS is found to be highly efficient
and stable electrocatalyst, which initiates the OER at an amazingly
low potential of 1.42 V (vs RHE). The NiO/NiS electrocatalyst provides
a current density of 40 mA cm–2 at 209 mV overpotential
for OER in 1.0 M KOH with a Tafel slope of 60 mV dec–1, outperforming its counterparts (NiO and NiS) under same electrochemical
conditions. These results are better than those of benchmark Ni-based
and even noble metal-based electrocatalysts. The continued oxygen
generation for several hours with an applied potential of 1.65 V (vs
RHE) reveals the long-term stability and activity of NiO/NiS electrocatalyst
toward OER. This development provides an attractive non-noble metal,
highly efficient, and stable electrocatalyst toward OER.
A novel strategy has been proposed
to produce in situ Li2S at the interfacial layer between
lithium anode and the solid electrolyte,
by using an amorphous-sulfide–LiTFSI–poly(vinylidene
difluoride) (PVDF) composite solid electrolyte (SLCSE). Besides retarding
the decomposition of PVDF in CSE, the Li2S-modified interfacial
layer (SMIL) also improves the wettability between lithium metal and
SLCSE which in turn optimizes the lithium deposition process. Our
density functional theory calculation results reveal that the migration
energy barrier of Li passing through SMIL is much lower than that
of Li passing through LiF-modified interfacial layer (FMIL) formed
from the decomposition of PVDF. The as-prepared SLCSE shows a Li ionic
transference number of 0.44 and Li ion conductivity of 3.42 ×
10–4 S/cm at room temperature, and the Li||SLCSE||LiFePO4 cell exhibits an outstanding rate performance with a capacity
of 153, 144, 131, and 101 mAh/g at a current density of 0.05, 0.10,
0.25, and 0.50 mA/cm2, respectively.
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