Currently, Pt single atoms as promising
electrocatalysts have been
applied to electrocatalysis aiming to significantly improve performance
and remarkably lower usage of the noble metal. Herein, we propose
a photochemical solid-phase reduction method to fabricate well-defined
isolated Pt atoms on a nitrogen-doped porous carbon (Pt1/NPC). Using this simple and fast synthesis strategy, the formed
Pt atoms are well-dispersed on the carbon without clusters or nanoparticles.
The loading of the Pt is up to 3.8 wt % relative to the carbon. The
Pt1/NPC catalyst displays an ultrahigh electrocatalytic
activity for hydrogen evolution reaction with an overpotential of
25 mV at the current density of 10 mA cm–2 and mass
activity of 2.86 A mg–1 Pt (24-times higher than
a commercial Pt/C). Moreover, the catalyst also presents efficient
catalytic activity for the oxygen reduction reaction. Its mass activity
is 4.3-times that obtained by a commercial Pt (20 wt %). The improved
electrocatalytic activities of the Pt1/NPC catalyst are
ascribed to the favorable chemical and electronic structure of the
Pt–N4 coordination raised by strong electron transfer
from the isolated Pt atoms to the coordinated N atoms in this catalyst.
The Pt1/NPC can be employed as a bifunctional catalyst
for fuel cells and hydrogen production.
The 3d transition metal and nitrogen co-doped carbon materials (TM-N-C) are considered as the most promising next-generation electrocatalysts, as alternatives to precious Pt, for the oxygen reduction reaction (ORR). Herein, we have fabricated a Cu-N-C catalyst through directly grafting copper-nitrogen complexes, composed by cuprous chloride and ammonia water, onto the surface of carbon black at 500 °C. In an alkaline environment, the synthesized catalyst exhibits excellent ORR catalytic activity, which is comparable to the state-of-the-art Pt/C catalyst, but far exceeding that obtained by the original carbon. Moreover, the catalyst displays much better stability than Pt/C. The enhanced ORR performance is proven to originate from the post-formation Cu -N and Cu -N sites at the carbon surface, as evidenced by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The possible ORR process catalyzed by these Cu-N species is discussed at the atomic level. This work provides a simple and fast synthesis strategy for efficient TM-N-C catalysts on a large scale for energy storage and conversion systems.
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