Abstract
The development of highly active, cheap and robust oxygen reduction reaction (ORR) electrocatalysts to replace precious metal platinum is extremely urgent and challenging for renewable energy devices. Herein we report a novel, green and especially facile hydrogel strategy to construct N and B co-doped nanocarbon embedded with Co-based nanoparticles as an efficient non-precious ORR catalyst. The agarose hydrogel provides a general host matrix to achieve a homogeneous distribution of key precursory components including cobalt (II) acetate and buffer salts, which, upon freeze-drying and carbonization, produces the highly active ORR catalyst. The gel buffer containing Tris base, boric acid and ethylenediaminetetraacetic acid, commonly adopted for pH and ionic strength control, plays distinctively different roles here. These include a green precursor for N- and B-doping, a salt porogen and a Co2+ chelating agent, all contributing to the excellent ORR activity. This hydrogel-based process is potentially generalizable for many other catalytic materials.
Highlights
Heteroatom-doped nanocarbons with promising electrocatalytic oxygen reduction reaction (ORR) activities[25,26,27]
After mixing the three components of TBE buffer, cobalt (II) acetate and agarose, the color of the mixture changed from pink to magenta due to the formation of a Co2+ -EDTA complex (Supplementary Figure S1, UV-vis data)
At this step, agarose appeared as a powdery solid that did not dissolve in the TBE buffer (Fig. 1a)
Summary
Heteroatom-doped nanocarbons with promising electrocatalytic ORR activities[25,26,27]. The as-obtained hydrogel-derived non-precious electrocatalyst (HNPC, hydrogel-derived non-precious catalyst) shows homogeneous microstructure, moderate heteroatom contents (12.6% Co, 5.26% N, and 3.26% B), high specific surface area (432 m2 g−1) and large mesopores (average pore diameter of 6.4 nm) with molecular accessibility, resulting in excellent four-electron ORR performance comparable to commercial Pt/C catalysts. This potentially general hydrogel-based strategy is inexpensive, environmentally benign and scalable, opening up a new catalytic material-oriented application of hydrogels. It is reasonable to expect that this unique strategy can be extended to other metal oxide or metal catalysts supported on N, B co-doped nanocarbons for energy-related applications
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