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1.
Chem Soc Rev ; 52(12): 3991-4005, 2023 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-37278085

RESUMO

Surface barriers to mass transfer in various nanoporous materials have been increasingly identified. These past few years especially, a significant impact on catalysis and separations has come to light. Broadly speaking, there are two types of barriers: internal barriers, which affect intraparticle diffusion, and external barriers, which determine the uptake and release rates of molecules into and out of the material. Here, we review the literature on surface barriers to mass transfer in nanoporous materials and describe how the existence and influence of surface barriers has been characterized, aided by molecular simulations and experimental measurements. As this is a complex, evolving research topic, without consensus from the scientific community at the time of writing, we present various current viewpoints, not always in agreement, on the origin, nature, and function of such barriers in catalysis and separation. We also emphasize the need for considering all the elementary steps of the mass transfer process in optimally designing new nanoporous and hierarchically structured adsorbents and catalysts.

2.
Angew Chem Int Ed Engl ; 63(24): e202404505, 2024 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-38598471

RESUMO

Ammonia borane (AB) with 19.6 wt % H2 content is widely considered a safe and efficient medium for H2 storage and release. Co-based nanocatalysts present strong contenders for replacing precious metal-based catalysts in AB hydrolysis due to their high activity and cost-effectiveness. However, precisely adjusting the active centers and surface properties of Co-based nanomaterials to enhance their activity, as well as suppressing the migration and loss of metal atoms to improve their stability, presents many challenges. In this study, mesoporous-silica-confined bimetallic Co-Cu nanoparticles embedded in nitrogen-doped carbon (CoxCu1-x@NC@mSiO2) were synthesized using a facile mSiO2-confined thermal pyrolysis strategy. The obtained product, an optimized Co0.8Cu0.2@NC@mSiO2 catalyst, exhibits enhanced performance with a turnover frequency of 240.9 molH2 ⋅ molmetal ⋅ min-1 for AB hydrolysis at 298 K, surpassing most noble-metal-free catalysts. Moreover, Co0.8Cu0.2@NC@mSiO2 demonstrates magnetic recyclability and extraordinary stability, with a negligible decline of only 0.8 % over 30 cycles of use. This enhanced performance was attributed to the synergistic effect between Co and Cu, as well as silica confinement. This work proposes a promising method for constructing noble-metal-free catalysts for AB hydrolysis.

3.
Small ; 19(25): e2301164, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-36919943

RESUMO

In recent years, growing concerns regarding energy efficiency and heat mitigation, along with the critical goal of carbon neutrality, have drawn human attention to the zero-energy-consumption cooling technique. Passive daytime radiative cooling (PDRC) can be an invaluable tool for combating climate change by dispersing ambient heat directly into outer space instead of just transferring it across the surface. Although significant progress has been made in cooling mechanisms, materials design, and application exploration, PDRC faces challenges regarding functionality, durability, and commercialization. Herein, a silica nanofiber aerogels (SNAs) functionalized poly(vinylidene fluoride-co-hexafluoropropene) (P(VDF-HFP)) membrane (SFP membrane), inspired by constructional engineering is constructed. As-prepared membranes with flexible network structure combined hierarchical structure design and practicability principal. As the host material for thermal comfort management (TCM) and versatile protection, the SFP membrane features a large surface area, porous structure, and a robust skeleton that can render excellent mechanical properties. Importantly, the SFP membrane can keep exceptional solar reflectivity (0.95) and strong mid-infrared emittance (0.98) drop the temperature to 12.5 °C below ambient and 96 W m-2 cooling power under typical solar intensities over 910 W m-2 . This work provides a promising avenue for high performance aerogel membranes that can be created for use in a wide variety of applications.

4.
Angew Chem Int Ed Engl ; 62(40): e202305371, 2023 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-37291046

RESUMO

Ammonia borane (AB) is a promising material for chemical H2 storage owing to its high H2 density (up to 19.6 wt %). However, the development of an efficient catalyst for driving H2 evolution through AB hydrolysis remains challenging. Therefore, a visible-light-driven strategy for generating H2 through AB hydrolysis was implemented in this study using Ni-Pt nanoparticles supported on phosphorus-doped TiO2 (Ni-Pt/P-TiO2 ) as photocatalysts. Through surface engineering, P-TiO2 was prepared by phytic-acid-assisted phosphorization and then employed as an ideal support for immobilizing Ni-Pt nanoparticles via a facile co-reduction strategy. Under visible-light irradiation at 283 K, Ni40 Pt60 /P-TiO2 exhibited improved recyclability and a high turnover frequency of 967.8 mol H 2 ${{_{{\rm H}{_{2}}}}}$ molPt -1 min-1 . Characterization experiments and density functional theory calculations indicated that the enhanced performance of Ni40 Pt60 /P-TiO2 originated from a combination of the Ni-Pt alloying effect, the Mott-Schottky junction at the metal-semiconductor interface, and strong metal-support interactions. These findings not only underscore the benefits of utilizing multipronged effects to construct highly active AB-hydrolyzing catalysts, but also pave a path toward designing high-performance catalysts by surface engineering to modulate the electronic metal-support interactions for other visible-light-induced reactions.

5.
Langmuir ; 38(38): 11621-11630, 2022 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-36107634

RESUMO

Clathrate hydrate growth, deposition, and plug formation during oil and gas transportation causes blockage of pipelines. An effective strategy to solve this problem is to mitigate the hydrate formation and reduce its adhesion on pipe walls through a coating process. However, durability failure, corrosion, inability to self-heal, high cost, and strong hydrate adhesion remain unsolved issues. To address these challenges, in this work, we present an in situ self-replenishing nonfluorinated durable hydrate-phobic coating of candle soot particles. The candle soot coating reduces hydrate adhesion by promoting a thick barrier film of hydrocarbons between the hydrate and the soot coated substrate. The hydrocarbons permeating the soot coating display a high contact angle for water and inhibit the formation of water bridges between the hydrate and soot coated substrate. The spherical cyclopentane hydrate slides off easily on the candle soot coating inside the cyclopentane environment. The hydrate former, cyclopentane-water emulsion, and THF-water mixture have high contact angles as well as low hydrate adhesion on soot coating simultaneously. In addition, the coating is flow-induced long-term slippery, durable, low cost, anticorrosion, self-cleaning, and suitable for practical applications.

6.
J Org Chem ; 87(6): 3978-3988, 2022 03 18.
Artigo em Inglês | MEDLINE | ID: mdl-35254832

RESUMO

Nitrogen, phosphorus, and oxygen codoped carbon catalysts were successfully synthesized using dried yeast powder as a pyrolysis precursor. The yeast-derived heteroatom-doped carbon (yeast@C) catalysts exhibited outstanding performance in the oxidation of Csp3-H bonds to ketones and esters, giving excellent product yields (of up to 98% yield) without organic solvents at low O2 pressure (0.1 MPa). The catalytic oxidation protocol exhibited a broad range of substrates (38 examples) with good functional group tolerance, excellent regioselectivity, and synthetic utility. The yeast-derived heteroatom-doped carbon catalysts showed good reusability and stability after recycling six times without any significant loss of activity. Experimental results and DFT calculations proved the important role of N-oxide (N+-O-) on the surface of yeast@C and a reasonable carbon radical mechanism.


Assuntos
Nitrogênio , Fermento Seco , Carbono/química , Catálise , Nitrogênio/química , Oxigênio , Fósforo , Saccharomyces cerevisiae
7.
Langmuir ; 36(37): 10960-10969, 2020 09 22.
Artigo em Inglês | MEDLINE | ID: mdl-32864968

RESUMO

Polluted water is a worldwide problem; therefore, effective separation of oil/water and removal of dyes, organic micropollutants, and heavy metals in wastewater are the need of the hour. Herein, hydrophilic ß-cyclodextrin-grafted carboxymethyl cellulose, biodegradable polyvinyl alcohol, and chitosan were used as main raw materials to construct a multifunctional aerogel framework by simple sol-gel and directional freeze-drying methods. Featuring intrinsic superamphiphilic wettability in air, robust superoleophobic wettability underwater, and excellent shape-recovery characteristics, the biomass-derived aerogel presents durable oil/water separation even after 10 cycles. The aerogels possess prominent adsorption capacity for methyl blue, 1-naphthylamine, and Cu2+, which was as high as 121.55 mg/g, 33.96 mg/g, and 122.6 mg/g, respectively. In addition, various pollutant mixtures could be effectively adsorbed by the aerogel at the same time with the adsorption capacity of 121.75 mg/g for methyl blue, 0.97 mg/g for bisphenol A, and 20.11 mg/g for Cu2+.

8.
J Am Chem Soc ; 140(40): 13071-13077, 2018 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-30222934

RESUMO

A selective CO evolution from photoreduction of CO2 in water was achieved on a noble-metal-free, carbide-based composite catalyst, as demonstrated by a CO selectivity of 98.3% among all carbon-containing products and a CO evolution rate of 29.2 µmol h-1, showing superiority to noble-metal-based catalyst. A rapid separation of the photogenerated electron-hole pairs and improved CO2 adsorption on the surface of the carbide component are responsible for the excellent performance of the catalyst. The high CO selectivity is accompanied by a predominant H2 evolution, which is believed to provide a proton-deficient environment around the catalyst to favor the formation of hydrogen-deficient carbon products. The present work provides general insights into the design of a catalyst with a high product selectivity and also the carbon evolution chemistry during a photocatalytic reaction.

9.
Small ; 10(21): 4249-56, 2014 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-25049062

RESUMO

An alkali-assisted cooperative assembly process of two different templating systems with aluminosilicate precursors is described. A highly ordered mesoporous zeolite with the 2D hexagonal symmetry mesospores and MFI zeolitic framework walls is synthesized. This method also allows the preparation of ZSM-5 with c- or b-axis-aligned mesopores. The materials have promising catalytic activities for organic reactions involving bulky molecules.

10.
RSC Adv ; 10(33): 19157-19168, 2020 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-35515474

RESUMO

Creating a robust omniphobic surface that repels various liquids would have broad technological implications for areas ranging from biomedical devices and fuel transport to architecture. The present omniphobic surfaces still have the problems of complex fabrication methods, high cost, and being environmentally harmful. To address these challenges, here we report a novel process to design a non-fluorinated, long-term slippery omniphobic surface of candle soot nanoparticles with a silicone binder that cures at room temperature. The porosity, nanoscale roughness, strong affinity of the substrate with the silicone lubricant, and retention of lubricant after curing of the binder play an important role in its stability and low ice adhesion strength at sub-zero temperature. The developed surface exhibits damage resistant slippery properties, repellency to several liquids with different surface tensions including blood, delay in freezing point along with ultra-low ice adhesion strength (2 kPa) and maintains it even below 7 kPa under harsh environmental conditions; 90 frosting/defrosting cycles at -90 °C; 2 months under an ice layer; 2 months at 60 °C; 9 days flow in acidic/basic water and exposure to super-cold water. In addition, this novel technique is cheap, easy to fabricate, environmentally benign and suitable for large-scale applications.

11.
ACS Appl Mater Interfaces ; 11(34): 31532-31542, 2019 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-31368296

RESUMO

Ice formation and accretion affect residential and commercial activities. Icephobic coatings decrease the ice adhesion strength (τice) to less than 100 kPa. However, rare icephobic coatings remove the ice under the action of gravity or natural winds. The icephobicity of such coatings depends on materials with low interfacial toughness. We develop durable candle soot icephobic coating with RTV-1 as a low-modulus binding material. Heterogeneous nucleation on 20-40 nm candle soot particles and their fracture mechanism are discussed. The developed coating always shows durable Cassie-Baxter superhydrophobic state with low ice adhesion (18 kPa) and maintains the τice value of about 25 kPa after severe mechanical abrasion, 30 liquid nitrogen/water cycles, 100 frosting/defrosting cycles, 100 icing/deicing cycles, acid/base exposure, under UV light, and exposure to natural freezing rain in Hangzhou. In addition, the proposed technique is time-efficient, inexpensive, and suitable for large-scale applications.

12.
ACS Appl Mater Interfaces ; 11(13): 12838-12845, 2019 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-30864773

RESUMO

Various organogel materials with either a liquid or solid surface layer have recently been designed and prepared. In this work, amphiphilic organogels (AmOG) are innovatively developed from copolymer P(PDMS-r-PEG-r-GMA) and 2,2'-diaminodiphenyldisulfide via epoxy group addition reaction and then infiltrated with amphiphilic lubricants instead of traditional hydrophilic or hydrophobic lubricants. Because of synergistic effects of hydrophilic and hydrophobic segments of amphiphilic lubricants, the AmOG surfaces showed high stability and excellent anti-icing performance. The delay in the freezing point of water was 1000 s on AmOG surfaces, which is 40 times longer as compared to the untreated hydrophilic glass surface. More importantly, low ice adhesion strength (15.1 kPa) was observed on AmOG which remained about 40 kPa even after 20 icing-deicing cycles. The novel amphiphilic organogels provide a new idea to prepare long-term anti-icing materials for practical applications.

13.
ACS Appl Mater Interfaces ; 11(50): 46800-46807, 2019 Dec 18.
Artigo em Inglês | MEDLINE | ID: mdl-31738044

RESUMO

In next generation lithium-ion batteries (LIBs), silicon is a promising electrode material due to its surprisingly high specific capacity, but it suffers from serious volume changes during the lithiation/delithiation process which gradually lead to the destruction of the electrode structure. A novel fluorinated copolymer with three different polar groups was synthesized to overcome this problem: carboxylic acid, amide, and fluorinated groups on a single polymer backbone. Moreover, a dual cross-linked network binder was prepared by thermal polymerization of the fluorinated copolymer and sodium alginate. Unlike the common chemical cross-linked network with a gradual and nonreversible fracturing, the dual cross-linked network which combines chemical and physical cross-linking could effectively hold the silicon particles during the volume change process. As a result, excellent electrochemical performance (1557 mAh g-1 at a 4 A g-1 current density after 200 cycles) was achieved with this novel reversible cross-linked binder. Further research studies with regard to the influences of fluorine and acrylamide content were conducted to systematically evaluate the designed binder. Moreover, with the help of new binder, the silicon/graphite and silicon oxide/graphite electrode exhibit superb cycle performance with capacity fade rate of 0.1% and 0.025% per cycle over 200 and 700 cycles, respectively. This novel and unsophisticated design gives a result for fabrication of high-performance Si based electrodes and advancement of the realization of practical application.

14.
Chem Commun (Camb) ; 51(48): 9785-8, 2015 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-25986474

RESUMO

This communication describes the fabrication of Pt/CeO2 nanotube@SiO2 core-shell catalysts applied to highly efficient water-gas shift reaction, where the initial CO conversion is 30.2% at 250 °C. Pt/CeO2 nanotube@SiO2 core-shell catalysts show outstanding thermal stability, even after accelerated aging under reaction conditions at 450 °C for 6 h, and the morphology is also unchanged after thermal treatment at 800 °C.


Assuntos
Cério/química , Nanotubos/química , Platina/química , Dióxido de Silício/química , Catálise , Temperatura Alta , Microscopia Eletrônica de Transmissão , Nanotubos/ultraestrutura , Povidona/química
15.
Bioresour Technol ; 143: 447-54, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23831743

RESUMO

In this work, density functional theory (DFT) was employed to investigate the reaction pathways of ß-D-glucopyranose for better understanding the pyrolysis mechanism of cellulose in hydrogen plasma. Many possible reactions were considered, and the reaction enthalpies and activation energies of these reactions were calculated using density functional theory (DFT) with a Gaussian method of B3LYP and basic set of 6-31G(d,p). A most possible reaction pathway was brought up. According to this reaction pathway, the main products of cellulose pyrolysis in hydrogen plasma would be syngas, and few light hydrocarbons. CO mainly comes from the decomposition of aldehyde group, while H2 mainly comes from dehydrogenation processes. Active H in plasma are found to play a very important role in many reactions, and they can remarkably lower the energies needed for reactions.


Assuntos
Glucosídeos/química , Hidrogênio/química , Celulose/química , Hidrocarbonetos/química , Hidrólise , Termodinâmica
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