In the past decade, atomically dispersed Fe active sites (coordinated with nitrogen) on carbon materials (FeNC) have emerged rapidly as promising single‐atom catalysts (SACs) for the oxygen reduction reaction (ORR) to substitute precious group metal (PGM) catalysts, owing to their earth abundance and low cost. Nonetheless, the production of highly active FeNC SACs is largely restricted by material cost, low product yield and difficulty of microstructure design. Herein, the authors demonstrate a facile in‐situ xerogel (ISG) assisted synthetic strategy, using cheap materials, to construct FeNC SACs (ISG FeNC). The porous silica xerogel, formed in‐situ with the FeNC precursors, encourages the emergence of enormous micropores/mesopores and homogeneous confinement/protection to the precursors during pyrolysis, benefiting to the formation of abundant accessible active sites (27.6 × 1019 sites g–1). Correspondingly, the ISG FeNC exhibits excellent ORR activity with a half‐wave potential (E1/2 = 0.91 V) in alkaline medium. The Zn–air battery assembled using the ISG FeNC SACs as the bifunctional catalyst of air cathode, demonstrates commendable performance with high peak power density of 249.1 mW cm–2 and superior long‐term stability (660 cycles with 220 h). This work offers an economic and efficient way to fabricate PGM‐free SACs for diverse applications.
The N-doped cobalt-based (Co) bifunctional single atom catalyst (SAC) has emerged as one of the most promising candidates to substitute noble metal-based catalysts for highly efficient bifunctionality. Herein, a facile silica xerogel strategy is elaborately designed to synthesize uniformly dispersed and dense Co-Nx active sites on N-doped highly porous carbon networks (Co-N-C SAC) using economic biomass materials. This strategy promotes the generation of massive mesopores and micropores for substantially improving the formation of Co-Nx moieties and unique network architecture. The Co-N-C SAC electrocatalysts exhibit an excellent bifunctional activity with a potential gap (ΔE) of 0.81 V in alkaline medias, outperforming those of the most highly active bifunctional electrocatalysts. On top of that, Co-N-C SAC also possesses outstanding performance in ZABs with superior power density/specific capacity. This proposed synthetic method will provide a new inspiration for fabricating various high-content SACs for varied applications.
Porous materials
can be modified with physical barriers to control the transport of
ions and molecules through channels via an external stimulus. Such
capability has brought attention toward drug delivery, separation
methods, nanofluidics, and point-of-care devices. In this context,
gated platforms on which access to an electrode surface of species
in solution can be reversibly hindered/unhindered on demand are appearing
as promising materials for sensing and microfluidic switches. The
preparation of a reversible gated device usually requires mesoporous
materials, nanopores, or molecularly imprinted polymers. Here, we
show how the breath-figure method assembly of graphene oxide can be
used as a simple strategy to produce gated electrochemical materials.
This was achieved by forming an organized porous thin film of graphene
oxide onto an ITO surface. Localized brushes of thermoresponsive poly(N-isopropylacrylamide) were then grown to specific sites
of the porous film by in situ reversible addition-fragmentation chain-transfer
polymerization. The gating mechanism relies on the polymeric chains
to expand and contract depending on the thermal stimulus, thus modulating
the accessibility of redox species inside the pores. The resulting
platform was shown to reversibly hinder or facilitate the electron
transfer of solution redox species by modulating temperature from
the room value to 45 °C or vice versa.
This manuscript reports a couple of novel polymers of side-chain functionalized PEDOT. The new polymers can be employed to successfully recognize 3,4-dihydroxyphenylalanine enantiomers and we also discuss the mechanism of chiral recognition.
Charge
carrier transfer efficiency as a crucial factor determines
the performance of heterogeneous photocatalysis. Here, we demonstrate
a simple nanohybrid structure of BaTiO3-Au (BTO-Au) for
the efficient selective oxidization of benzyl alcohol to benzaldehyde
upon piezotronic effect boosted plasmonic photocharge carrier transfer.
With the aid of ultrasonic mechanical vibration, the reaction rate
of the photocatalytic organic conversion would be considerably accelerated,
which is about 4.2 and 6.2 times higher than those driven by sole
visible light irradiation and sole ultrasonication, respectively.
Photoelectrochemical tests under ultrasonic stimuli reveal the BTO-Au
catalytic system is independent of the light intensity, showing a
consistent photocurrent density, over a wide range of incident light
brightness. The largely enhanced photocatalytic activity can be ascribed
to the synergetic effect of surface plasmonic resonance (SPR)–piezotronic
coupling by which a built-in electric field induced by the piezotronic
effect significantly favors the oriented mobilization of energetic
charge carriers generated by the SPR effect at the heterojunction.
Notably, a decrease of the Schottky barrier height of ∼0.3
eV at the BTO-Au interface is verified experimentally, due to the
band bending of BTO induced by the piezotronic effect, which can greatly
augment the hot electron transfer efficiency. This work highlights
the coupling of the piezotronic effect with SPR within the BTO-Au
nanostructure as a versatile and promising route for efficient charge
transfer in photocatalytic organic conversion.
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