Manganese dioxide (MnO2) represents a promising oxygen
reduction reaction (ORR) electrocatalyst, but its catalytic activity
is largely limited by the essentially low electronic conductivity
and large geometric size. Herein, hierarchical ε-MnO2 nanosheets (MnO2-H) strongly coupled with silver nanoparticle
spheres (Ag NPs) were developed. The introduced Ag NPs can not only
enhance the electronic transfer but also tune the electronic structure
of MnO2 and act as active sites for ORR. Owing to the large
electrochemically active surface area, good mass/electronic transfer,
and a strong coupled interface between MnO2-H and Ag NPs,
the optimal Ag-MnO2-H-1.53 showed much higher catalytic
activity than MnO2-H, Ag microparticles, and commercial
Pt/C catalyst for ORR. Moreover, Ag-MnO2-H-1.53 displayed
robust catalytic stability with negligible shift in the half-wave
potential after 5000 cycles. As a cathode catalyst, a homemade zinc–air
battery (ZAB) based on Ag-MnO2-H-1.53 showed a high open
circuit voltage (1.52 V), maximum peak power density (120.2 mW/cm2), and specific capacity (646 mAh/g) superior to those of
Pt/C-based ZAB (1.48 V, 82.3 mW/cm2, and 612 mAh/g), along
with a long lifetime. This work highlights the significance of strong
interface coupling between MnO2-H and Ag NPs for boosting
the ORR electrocatalysis, which will inspire more work for the rational
design of efficient carbon-free transition metal electrocatalysts
for energy conversion.
Selectively creating active sites those can work well in different medium as much as possible remains an open challenge for the widespread application of sustainable metal air batteries and fuel...
Developing earth-abundant materials with efficient oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) catalysis in both alkalin and acidic medium is of significance for hydrogen fuel cells application. Herein,...
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