Hydrogel is used as a structural template and precursor to prepare carbon aerogel doped with Fe–Co bimetal sites as bifunctional catalysts for ORR and OER, which exhibits enhanced activity and stability, as compared to the monometal counterparts.
Design and engineering of bifunctional catalysts are critical in the development of electrochemical full water splitting. In this study, 4-ethylphenylacetylene-functionalized iridium (Ir− C, 1.7 ± 0.3 nm in diameter) nanoparticles are found to exhibit markedly enhanced electrocatalytic activity toward both hydrogen and oxygen evolution reactions (HER and OER) in acidic and alkaline media, in comparison to the nanoparticles capped with mercapto and nitrene derivatives. Remarkably, the HER and OER performances in alkaline media are even better than those of commercial Ir/C and Pt/C benchmarks. This is accounted for by the formation of Ir−CC− conjugated interfacial linkage that leads to significant intraparticle charge delocalization and hence manipulation of the electron density of the Ir nanoparticles and interactions with key reaction intermediates. This is indeed confirmed by results from both spectroscopic measurements and density functional theory calculations. With Ir−C nanoparticles as both the cathode and anode catalysts for electrochemical water splitting, a low cell voltage of 1.495 and 1.473 V is needed to reach the current density of 10 mA cm −2 in alkaline and acidic media, respectively. Such a performance is markedly better than that of commercial Ir/C (1.548 and 1.561 V) and relevant catalysts reported in recent literature, highlighting the significance of interfacial engineering in the development of high-performance bifunctional electrocatalysts.
Metal–nitrogen–carbon
(MNC) nanocomposites have been
hailed as promising and efficient electrocatalysts toward oxygen reduction
reaction (ORR), due to the formation of MN
x
coordination moieties. However, MNC hybrids are mostly prepared
by pyrolysis of organic precursors along with select metal salts,
where part of the MN
x
sites are inevitably
buried in the carbon matrix. This limited accessibility compromises
the electrocatalytic performance. Herein, we describe a wet-impregnation
procedure by facile thermal refluxing, whereby palladium is atomically
dispersed and enriched onto the surface of hollow, nitrogen-doped
carbon cages (HNC) forming Pd–N coordination bonds. The obtained
Pd-HNC nanocomposites exhibit an ORR activity in alkaline media markedly
higher than that of metallic Pd nanoparticles, and the best sample
even outperforms commercial Pt/C and relevant Pd-based catalysts reported
in the literature. The results suggest that atomic dispersion and
surface enrichment of palladium in a carbon matrix may serve as an
effective strategy in the fabrication of high-performance ORR electrocatalysts.
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