In
this study, we report a facile synthetic pathway to three-dimensional
(3D) Pd nanosponge-shaped networks wrapped by graphene dots (Pd@G-NSs),
which show superior electrocatalytic activity toward the hydrogen
evolution reaction (HER) and exhibited excellent long-term stability
in acidic media. Pd@G-NSs were synthesized by simply mixing Pd precursors,
reducing agent, carbon dots (Cdots), and Br– ion
at 30 °C. Experimental results and density functional theory
(DFT) calculations suggested that the Br– ions played
an essential role in accelerating the exfoliation of Cdot, supplying
graphene layers, which could wrap the nanosponge-shaped Pd and finally
form Pd@G-NS. In the absence of the Br– ions, only
aggregated Pd nanoparticles (NPs) were formed and randomly mixed with
Cdots. The resultant Pd@G-NS exhibited a high electrochemically active
surface area and accelerated charge transport characteristics, leading
to its superior electrocatalytic activity toward the HER in acidic
media. The HER overpotential of Pd@G-NS was 32 mV at 10 mA cm–2, and the Tafel slope was 33 mV dec–1. Furthermore, the unique Pd@G-NS catalyst showed long-term stability
for over 3000 cycles in acidic media as well, owing to the protection
of Pd nanosponges by graphene dot wrapping. The overall HER performance
of the Pd@G-NS catalyst exceeded that of commercial Pt/C.
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