To cater for the development of clean
hydrogen energy, an efficient
oxygen evolution reaction catalyst is urgently needed to increase
the efficiency of water splitting. A novel three-dimensional (3D)
ternary transition metal hydroxide, FeCoNi-layered double hydroxide
(FeCoNi-LDH) nanocage has been successfully synthesized by the cation
exchange reaction using the metal–organic framework as a template.
The obtained ternary FeCoNi-LDH nanocage displays excellent electrocatalytic
activity, such as the low overpotential of 299 mV at j = 10 mA cm–2 in 1.0 M KOH electrolyte with a Tafel
slope of 50 mV dec–1. Moreover, the FeCoNi-LDH nanocage
could also be used as a high-performance electrode for supercapacitor,
which presents a high specific capacity of 980 F g–1 at 1 A g–1 in 3.0 M KOH. More importantly, the
electrode possesses a superb rate capability with 93% capacity retention
even at a current density of 20 A g–1. These results
manifest that FeCoNi-LDH has a wide prospect in the application in
the energy conversion and storage fields.
Organic–inorganic halide perovskites
have attracted increasing interest for solar-energy harvesting because
of the simple fabrication process, high efficiency, and low cost.
In this work, we systematically investigate the structural and electronic
properties, and stability of two-dimensional (2D) hybrid organic–inorganic
perovskites (HOIPs) based on density-functional-theory calculations.
We explore a general rule to predict the bandgap of the 2D HOIP: its
bandgap decreases as the thickness increases and the size of metal
atom decreases as well as that of the halide atom increases. We find
that effective mass of hole increases as the thickness of 2D HOIP
increases. Importantly, the 2D HOIPs exhibit high stability on the
resistance of water and oxygen than bulk HOIPs due to high positive
adsorption energy. Our results confirm that the 2D HOIPs may be excellent
alternatives to the unstable bulk HOIPs in solar energy harvesting
with improved performance due to suitable bandgap, small carrier effective
mass, and high resistance to water and oxygen molecules.
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