Surface wettability of active sites plays a crucial role in the activity and selectivity of catalysts. This report describes modification of surface hydrophobicity of Pd/UiO‐66, a composite ...comprising a metal–organic framework (MOF) and stabilized palladium nanoparticles (NPs), using a simple polydimethylsiloxane (PDMS) coating. The modified catalyst demonstrated significantly improved catalytic efficiency. The approach can be extended to various Pd nanoparticulate catalysts for enhanced activity in reactions involving hydrophobic reactants, as the hydrophobic surface facilitates the enrichment of hydrophobic substrates around the catalytic site. PDMS encapsulation of Pd NPs prevents aggregation of NPs and thus results in superior catalytic recyclability. Additionally, PDMS coating is applicable to a diverse range of catalysts, endowing them with additional selectivity in sieving reactants with different wettability.
Hydrophobic visions: Surface hydrophobization of Pd/UiO‐66, a composite of a metal–organic framework (MOF) and stabilized palladium nanoparticles, was realized using a simple polydimethylsiloxane (PDMS) coating. The resultant Pd/UiO‐66@PDMS composite exhibits superior catalytic activity and recyclability compared to pristine Pd/UiO‐66, and additional selectivity in sieving reactants with different wettability. This approach is extendable to various Pd‐based catalysts.
Exploring low‐cost and high‐performance nonprecious metal catalysts (NPMCs) for oxygen reduction reaction (ORR) in fuel cells and metal–air batteries is crucial for the commercialization of these ...energy conversion and storage devices. Here we report a novel NPMC consisting of Fe3C nanoparticles encapsulated in mesoporous Fe‐N‐doped carbon nanofibers, which is synthesized by a cost‐effective method using carbonaceous nanofibers, pyrrole, and FeCl3 as precursors. The electrocatalyst exhibits outstanding ORR activity (onset potential of −0.02 V and half‐wave potential of −0.140 V) closely comparable to the state‐of‐the‐art Pt/C catalyst in alkaline media, and good ORR activity in acidic media, which is among the highest reported activities of NPMCs.
Nanocomposite electrocatalyst: A high‐performance electrocatalyst for the oxygen reduction reaction (ORR) is based on Fe3C nanoparticles encapsulated in mesoporous Fe‐N‐doped carbon nanofibers. It can be synthesized from low‐cost and abundant precursors and exhibits excellent electrocatalytic performance for the ORR in both alkaline and acidic media.
The incorporation of defects, such as vacancies, into functional materials could substantially tailor their intrinsic properties. Progress in vacancy chemistry has enabled advances in many ...technological applications, but creating new type of vacancies in existing material system remains a big challenge. We show here that ionized nitrogen plasma can break bonds of iron-carbon-nitrogen-nickel units in nickel-iron Prussian blue analogues, forming unconventional carbon-nitrogen vacancies. We study oxygen evolution reaction on the carbon-nitrogen vacancy-mediated Prussian blue analogues, which exhibit a low overpotential of 283 millivolts at 10 milliamperes per square centimeter in alkali, far exceeding that of original Prussian blue analogues and previously reported oxygen evolution catalysts with vacancies. We ascribe this enhancement to the in-situ generated nickel-iron oxy(hydroxide) active layer during oxygen evolution reaction, where the Fe leaching was significantly suppressed by the unconventional carbon-nitrogen vacancies. This work opens up opportunities for producing vacancy defects in nanomaterials for broad applications.
Abstract
Single-atom catalysts (SACs) have sparked broad interest recently while the low metal loading poses a big challenge for further applications. Herein, a dual protection strategy has been ...developed to give high-content SACs by nanocasting SiO
2
into porphyrinic metal–organic frameworks (MOFs). The pyrolysis of SiO
2
@MOF composite affords single-atom Fe implanted N-doped porous carbon (Fe
SA
–N–C) with high Fe loading (3.46 wt%). The spatial isolation of Fe atoms centered in porphyrin linkers of MOF sets the first protective barrier to inhibit the Fe agglomeration during pyrolysis. The SiO
2
in MOF provides additional protection by creating thermally stable FeN
4
/SiO
2
interfaces. Thanks to the high-density Fe
SA
sites, Fe
SA
–N–C demonstrates excellent oxygen reduction performance in both alkaline and acidic medias. Meanwhile, Fe
SA
–N–C also exhibits encouraging performance in proton exchange membrane fuel cell, demonstrating great potential for practical application. More far-reaching, this work grants a general synthetic methodology toward high-content SACs (such as Fe
SA
, Co
SA
, Ni
SA
).
Thirsty fibers: The aerogels described in the title can be fabricated in large scale by using a low‐cost biomass, bacterial cellulose, as a precursor, which can be produced at industrial level in a ...microbial fermentation process. The carbon nanofiber aerogels (black pieces in picture) exhibit superior absorption capacity for organic solvents (red solution) and high potential for pressure sensing.
The high viscosity and low fluidity of heavy crude oil hinder its sorption by conventional porous sorbents, so the efficient clean‐up of such heavy crude oil spills is challenging. Recently, Joule ...heating has been emerging as a new tool to reduce the viscosity of heavy crude oil dramatically. However, this direct‐contact heating approach presents a potential risk due to the high voltage applied. To develop a non‐contact recovery of viscous crude oil, here, a new approach for the fabrication of a series of ferrimagnetic sponges (FMSs) with hydrophobic porous channels is reported, whose surface can be remotely heated to 120 °C within 10 s under an alternating magnetic field (f = 274 kHz, H = 30 kA m−1). Compared with the solar‐driven superficial heating, the integral magnetic heating in FMSs can result in a higher internal temperature of the sponges because of the confinement of thermal transport in the porous channels, which contributes to a dramatic decrease in oil viscosity and a significant increase in oil flow into the pores of FMSs. Furthermore, FMSs assembled with a self‐priming pump can achieve continuous recovery of viscous crude oil (33.05 g h−1 cm−2) via remotely magnetic heating.
A ferrimagnetic sponge with the skeletons coated with poly(dimethylsiloxane) and iron oxide nanoparticles is developed to achieve continuous recovery of viscous crude oil. Under the exposure of an alternating magnetic field, the viscosity of the viscous oil around the sponge decreases sharply, thus accelerating its absorption.
It is still a great challenge to improve deformability and fatigue-resistance of stretchable conductors when maintaining their high-level conductivity for practical use. Herein, a high-performance ...stretchable conductor with hierarchically ternary network and self-healing capability is demonstrated through in situ polymerizing N-isopropylacrylamide (NIPAM) on well-defined sulfur-containing molecule-modified Ag nanowire (AgNW) aerogel framework. Owing to hierarchical architecture from nanoscale to microscale and further to macroscale and strong interactions of polymer chains and AgNWs, the composite exhibits good conductivity of 93 S cm
, excellent electromechanical stability up to superhigh tensile strain of 800% and strong fatigue-resistant ability through well accommodating the applied deformations and sharing external force in the network. Furthermore, the composite delivers a fast and strong healing capability induced by reversible Ag-S bonds, which enables the healed conductor to hold an impressive electromechanical property. These prominent demonstrations confirm this material as top performer for use as flexible, stretchable electronic devices.
Metal‐based materials with exceptional intrinsic conductivity own excellent electromagnetic interference (EMI) shielding performance. However, high density, corrosion susceptibility, and poor ...flexibility of the metal severely restrict their further applications in the areas of aircraft/aerospace, portable and wearable smart electronics. Herein, a lightweight, flexible, and anticorrosive silver nanowire wrapped carbon hybrid sponge (Ag@C) is fabricated and employed as ultrahigh efficiency EMI shielding material. The interconnected Ag@C hybrid sponges provide an effective way for electron transport, leading to a remarkable conductivity of 363.1 S m−1 and superb EMI shielding effectiveness of around 70.1 dB in the frequency range of 8.2–18 GHz, while the density is as low as 0.00382 g cm−3, which are among the best performances for electrically conductive sponges/aerogels/foams by far. More importantly, the Ag@C sponge surprisingly exhibits super‐hydrophobicity and strong corrosion resistance. In addition, the hybrid sponges possess excellent mechanical resilience even with a large strain (90% reversible compressibility) and an outstanding cycling stability, which is far better than the bare metallic aerogels, such as silver nanowire aerogels and copper nanowire foams. This strategy provides a facile methodology to fabricate lightweight, flexible, and anticorrosive metal‐based sponge for highly efficient EMI shielding applications.
Anticorrosive, ultralightweight, and flexible silver nanowire wrapped with carbon hybrid sponge is designed and employed as electromagnetic interference (EMI) shielding material with ultrahigh efficiency. The interconnected hybrid sponge shows superb EMI shielding effectiveness of 70.1 dB, while the density is as low as 0.00382 g cm−3, which are among the best performances for electrically conductive sponges/aerogels/foams by far.
The chemical environment of metal nanoparticles (NPs) possesses significant influence on their catalytic performance yet is far from being well understood. Herein, tiny Pd NPs are encapsulated into ...the pore space of metal–organic frameworks (MOFs), UiO‐66‐X (X = H, OMe, NH2, 2OH, 2OH(Hf)), affording Pd@UiO‐66‐X composites. The surface microenvironment of the Pd NPs is readily modulated by pore wall engineering, via the functional group and metal substitution in the MOFs. Consequently, the catalytic activity of Pd@UiO‐66‐X follows the order of Pd@UiO‐66‐OH > Pd@UiO‐66‐2OH(Hf) > Pd@UiO‐66‐NH2 > Pd@UiO‐66‐OMe > Pd@UiO‐66‐H toward the hydrogenation of benzoic acid. It is found that the activity difference is not only ascribed to the distinct charge transfer between Pd and the MOF, but is also explained by the discriminated substrate adsorption energy of Pd@UiO‐66‐X (–OH < –2OH(Hf) < –NH2 < –OMe < –H), based on CO‐diffuse reflectance infrared Fourier transform spectra and density‐functional theory (DFT) calculations. The Pd@UiO‐66‐OH, featuring a high Pd electronic state and moderate adsorption energy, displays the highest activity. This work highlights the influence of the surface microenvironment of guest metal NPs, the catalytic activity of which is dominated by electron transfer and the adsorption energy, via the systematic substitution of metal and functional groups in host MOFs.
Pd nanoparticles (NPs) encapsulated into UiO‐66‐X (X = H, OMe, NH2, 2OH, 2OH(Hf)) show drastically different activities toward the hydrogenation of benzoic acid. This work highlights the influence of the surface microenvironment of guest metal NPs, the catalytic activity of which is dominated by electron transfer and the adsorption energy, via the systematic modification of host metal–organic frameworks (MOFs).
Composite nanomaterials usually possess synergetic properties resulting from the respective components and can be used for a wide range of applications. In this work, a Pd nanocubes@ZIF‐8 composite ...material has been rationally fabricated by encapsulation of the Pd nanocubes in ZIF‐8, a common metal–organic framework (MOF). This composite was used for the efficient and selective catalytic hydrogenation of olefins at room temperature under 1 atm H2 and light irradiation, and benefits from plasmonic photothermal effects of the Pd nanocube cores while the ZIF‐8 shell plays multiple roles; it accelerates the reaction by H2 enrichment, acts as a “molecular sieve” for olefins with specific sizes, and stabilizes the Pd cores. Remarkably, the catalytic efficiency of a reaction under 60 mW cm−2 full‐spectrum or 100 mW cm−2 visible‐light irradiation at room temperature turned out to be comparable to that of a process driven by heating at 50 °C. Furthermore, the catalyst remained stable and could be easily recycled. To the best of our knowledge, this work represents the first combination of the photothermal effects of metal nanocrystals with the favorable properties of MOFs for efficient and selective catalysis.
The incorporation of palladium nanocubes (NCs) into the metal–organic framework ZIF‐8 affords the composite Pd NCs@ZIF‐8, which was utilized for the efficient catalytic hydrogenation of olefins at room temperature under light irradiation. The superior catalytic performance is due to the plasmonic photothermal effects of Pd NCs and the multiple roles (H2 enrichment, size sieving, and Pd stabilization) of the ZIF‐8 shell.
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