We
have demonstrated the synthesis of defect-rich Ni-doped MoSe2 nanoplates (NiMoSe2) and their application as
an efficient electrocatalyst for enzymatic biofuel cells and electrochemical
pseudocapacitors. In this study, a new type of interpretation is proposed
that a defective surface facilitates the effective entrapment of enzymes
(glucose oxidase (GOD), laccase) for biofuel cells and additional
ion diffusion for Faradic charge–discharge reaction. The transmission
electron microscopy and UV–vis spectroscopy techniques scrutinized
the formation of defects/distortions and the resultant successful
entrapment of enzymes. The performed electrochemical characterizations
of enzyme-immobilized NiMoSe2/nickel foam (NF) bioanode
(NiMoSe2/GOD/NF) and biocathode (NiMoSe2/laccase/NF)
exhibited better direct charge conductive behavior at the interface
of enzymes and electrode material. Herein, the assembled biofuel cells
exhibited an open-circuit voltage (V
OC = 0.6 V) and a short-circuit current density (J
SC = 8.629 mA cm–2) with a maximum power
density (P
max) of 1.2 mW cm–2. For the electrochemical pseudocapacitor application, the proposed
NiMoSe2/NF exhibited excellent specific capacitance (535.74
F g–1), with 86.7% rate performance. Finally, this
work suggests new insights into both enzymatic biofuel cell and supercapacitor
applications.
The exploration of heterostructure materials with unique
electronic
properties is considered a desirable platform for fabricating electrode/surface
interface relationships for constructing asymmetric supercapacitors
(ASCs) with high energy density. In this work, a heterostructure based
on amorphous nickel boride (Ni
X
B) and
crystalline square bar-like manganese molybdate (MnMoO4) was prepared by a simple synthesis strategy. The formation of the
Ni
X
B/MnMoO4 hybrid was confirmed
by powder X-ray diffraction (p-XRD), field emission scanning electron
microscopy (FE-SEM), field-emission transmission electron microscopy
(FE-TEM), Brunauer–Emmett–Teller (BET), Raman, and X-ray
photoelectron spectroscopy (XPS). In this hybrid system (Ni
X
B/MnMoO4), the intact combination of Ni
X
B and MnMoO4 leads to a large
surface area with open porous channels and abundant crystalline/amorphous
interfaces with a tunable electronic structure. This Ni
X
B/MnMoO4 hybrid shows high specific capacitance
(587.4 F g–1) at 1 A g–1, and
it even retains a capacitance of 442.2 F g–1 at
10 A g–1, indicating superior electrochemical performance.
The fabricated Ni
X
B/MnMoO4 hybrid
electrode also exhibited an excellent capacity retention of 124.4%
(10000 cycles) and a Coulombic efficiency of 99.8% at a current density
of 10 A g–1. In addition, the ASC device (Ni
X
B/MnMoO4//activated carbon) achieved
a specific capacitance of 104 F g–1 at 1 A g–1 and delivered a high energy density of 32.5 Wh.kg–1 with a power density of 750 W·kg–1. This exceptional electrochemical behavior is due to the ordered
porous architecture and the strong synergistic effect of Ni
X
B and MnMoO4, which enhances the accessibility
and adsorption of OH– ions that improve electron
transport. Moreover, the Ni
X
B/MnMoO4//AC device exhibits excellent cyclic stability with a retention
of 83.4% of the original capacitance after 10000 cycles, which is
due to the heterojunction layer between Ni
X
B and MnMoO4 that can improve the surface wettability
without causing structural changes. Our results show that the metal
boride/molybdate-based heterostructure is a new category of high-performance
and promising material for the growth of advanced energy storage devices.
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