and Technology (HKUST). He is now a professor of the College of Civil and Transportation Engineering of Shenzhen University. His research interests include structure and corrosion inhibition materials of coastal concrete and their durability evaluation.
The rational design
of excellent electrocatalysts is significant
for triggering the slow kinetics of oxygen reduction reaction (ORR)
and oxygen evolution reaction (OER) in rechargeable metal–air
batteries. Hereby, we report a bifunctional catalytic material with
core–shell structure constructed by Co3O4 nanowire arrays as cores and ultrathin NiFe-layered double hydroxides
(NiFe LDHs) as shells (Co3O4@NiFe LDHs). The
introduction of Co3O4 nanowires could provide
abundant active sites for NiFe LDH nanosheets. Most importantly, the
deposition of NiFe LDHs on the surface of Co3O4 can modulate the surface chemical valences of Co, Ni, and Fe species
via changing the electron donor and/or electron absorption effects,
finally achieving the balance and optimization of ORR and OER properties.
By this core–shell design, the maximum ORR current densities
of Co3O4@NiFe LDHs increase to 3–7 mA
cm–2, almost an order of magnitude increases compared
to pure NiFe LDH (0.45 mA cm–2). Significantly,
an OER overpotential as low as 226 mV (35 mA cm–2) is achieved in the designed core–shell catalyst, which is
comparable to and/or even better than those of commercial Ir/C. Hence,
the primary zinc–air battery employing Co3O4@NiFe LDH as an air electrode achieves a high specific capacity
(667.5 mA h g–1) and first-class energy density
(797.6 W h kg–1); the rechargeable battery can show
superior reversibility, excellent stability, and voltage gaps of ∼0.8
V (∼60% of round-trip efficiency) in >1200 continuous cycles.
Furthermore, the flexible quasi-solid-state zinc–air battery
with bendable ability holds practical potential in portable and wearable
electronic devices.
Bimetallic phosphides have been identified as promising alternative electrode materials owing to their admirable conductivity and electrochemical activity.
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