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1.
Chem Asian J ; : e202400296, 2024 Jun 18.
Article in English | MEDLINE | ID: mdl-38889347

ABSTRACT

Formic acid (HCOOH) is a highly energy-efficient product of electrochemical CO2 reduction reaction (CO2RR). Bismuth-based catalysts have shown promise in the conversion of CO2 to formic acid, but there is still a great need for further improvement in selectivity and activity. Herein, we report the preparation of Bi nanosheets decorated by cerium oxide nanoparticles (CeOx) with high Ce3+/Ce4+ ratio and rich oxygen vacancies. The CeOx nanoparticles affect on the electronic structures of bismuth, enhance the CO2 adsorption, and thus promote the CO2RR properties of Bi nanosheets. Compared with elemental Bi nanosheets, the hetero-structured CeOx/Bi nanosheets exhibit much higher activity over a wide potential window, showing a current density of 16.1 mA cm-2 with a  Faradaic efficiency of 91.1% at -0.9 V vs. reversible hydrogen electrode.

2.
J Am Chem Soc ; 146(2): 1572-1579, 2024 Jan 17.
Article in English | MEDLINE | ID: mdl-38170986

ABSTRACT

CO2 electroreduction holds great promise for addressing global energy and sustainability challenges. Copper (Cu) shows great potential for effective conversion of CO2 toward specific value-added and/or high-energy-density products. However, its limitation lies in relatively low product selectivity. Herein, we present that the CO2 reduction reaction (CO2RR) pathway on commercially available Cu can be rationally steered by modulating the microenvironment in the vicinity of the Cu surface with two-dimensional sulfonated covalent organic framework nanosheet (COF-NS)-based ionomers. Specifically, the selectivity toward methane (CH4) can be enhanced to more than 60% with the total current density up to 500 mA cm-2 in flow cells in both acidic (pH = 2) and alkaline (pH = 14) electrolytes. The COF-NS, characterized by abundant apertures, can promote the accumulation of CO2 and K+ near the catalyst surface, alter the adsorption energy and surface coverage of *CO, facilitate the dissociation of H2O, and finally modulate the reaction pathway for the CO2RR. Our approach demonstrates the rational modulation of reaction interfaces for the CO2RR utilizing porous open framework ionomers, showcasing their potential practical applications.

3.
Small ; 19(34): e2301639, 2023 Aug.
Article in English | MEDLINE | ID: mdl-37093197

ABSTRACT

Two-dimensional low-melting-point (LMP) metal nanocrystals are attracting increasing attention with broad and irreplaceable applications due to their unique surface and topological structures. However, the chemical synthesis, especially the fine control over the nucleation (reduction) and growth (crystallization), of such LMP metal nanocrystals remains elusive as limited by the challenges of low standard redox potential, low melting point, poor crystalline symmetry, etc. Here, a controllable reduction-melting-crystallization (RMC) protocol to synthesize free-standing and surfactant-free bismuth nanocrystals with tunable dimensions, morphologies, and surface structures is presented. Especially, ultrathin bismuth nanosheets with flat or jagged surfaces/edges can be prepared with high selectivity. The jagged bismuth nanosheets, with abundant surface steps and defects, exhibit boosted electrocatalytic CO2 reduction performances in acidic, neutral, and alkaline aqueous solutions, achieving the maximum selectivity of near unity at the current density of 210 mA cm-2 for formate evolution under ambient conditions. This work creates the RMC pathway for the synthesis of free-standing two-dimensional LMP metal nanomaterials and may find broader applicability in more interdisciplinary applications.

4.
ACS Appl Mater Interfaces ; 15(16): 20317-20324, 2023 Apr 26.
Article in English | MEDLINE | ID: mdl-37057844

ABSTRACT

Electrochemical CO2 reduction reaction (CO2RR), which uses renewable electricity to produce high-value-added chemicals, offers an alternative clean path to the carbon cycle. However, bismuth-based catalysts show great potential for the conversion of CO2 and water to formate, but their overall efficiency is still hampered by the weak CO2 adsorption, low electrical conductivity, and slow mass transfer of CO2 molecules. Herein, we report that a rationally modulated nitrogen-doped graphene aerogel matrix (NGA) can significantly enhance the CO2RR performance of bismuth nanoplates (BiNPs) by both modulating the electronic structure of bismuth and regulating the interface for chemical reaction and mass transfer environments. In particular, the NGA prepared by reducing graphene oxide (GO) with hydrazine hydrate (denoted as NGAhdrz) exhibits significantly enhanced strong metal-support interaction (SMSI), increased specific surface area, strengthened CO2 adsorption, and modulated wettability. As a result, the Bi/NGAhdrz exhibits significantly boosted CO2RR properties, with a Faradaic efficiency (FE) of 96.4% at a current density of 51.4 mA cm-2 for formate evolution at a potential of -1.0 V versus reversible hydrogen electrode (vs RHE) in aqueous solution under ambient conditions.

5.
Chem Asian J ; 18(9): e202300110, 2023 May 02.
Article in English | MEDLINE | ID: mdl-36935350

ABSTRACT

CO2 reduction reactions (CO2 RR) powered by renewable electricity can directly convert CO2 to hydrocarbons and fix the sustainable but intermittent energy (e. g., sunlight, wind, etc.) in stable and portable chemical fuels. Advanced catalysts boosting CO2 RR with high activity, selectivity, and durability at low overpotentials are of great importance but still elusive. Here, we report that the ultrathin Pd-Ag dendritic nanoplates (PdAg DNPs) exhibited boosted activity, selectivity, and stability for producing formate from CO2 at a very low overpotential in aqueous solutions under ambient conditions. As a result, the PdAg DNPs exhibited a Faradaic efficiency (FE) for formate of 91% and a cathodic energy efficiency (EE) of ∼90% at the potential of -0.2 V versus reversible hydrogen electrode (vs. RHE), showing significantly enhanced durability as compared with pure Pd catalysts. Our strategy represents a rational catalyst design by engineering the surface geometrical and electronic structures of metal nanocrystals and may find more applicability in future electrocatalysis.

6.
ChemSusChem ; 15(24): e202201324, 2022 Dec 20.
Article in English | MEDLINE | ID: mdl-36066561

ABSTRACT

A distinct platinum oxide nanocluster (PtOx ) was developed, consisting of only Pt-O bond by a defect-engineered Al metal-organic framework (MOF) (BIT-72) with superior formaldehyde (HCHO) degradation activity and stability. With only 0.015 wt % Pt loading, PtOx @BIT-72-DE could degrade HCHO with 100 % conversion continuously for at least 200 h under HCHO concentration of 25 ppm and gas hourly space velocity of 60000 mL g-1 h-1 at room temperature. Furthermore, its specific rate (446 mmolHCHO gPt -1 h-1 ) was higher than for traditional Pt-based catalysts and single-atom Pt catalysts. Moreover, the cost of PtOx @BIT-72-DE was lowered to 0.0769 $ g-1 , which could significantly facilitate its commercial application. This study demonstrates the promising potential of MOFs in the design of HCHO degradation catalysts.


Subject(s)
Metal-Organic Frameworks , Oxidation-Reduction , Oxides , Platinum/chemistry , Formaldehyde/chemistry
7.
ChemSusChem ; 15(10): e202200211, 2022 May 20.
Article in English | MEDLINE | ID: mdl-35266642

ABSTRACT

The electrocatalytic properties of metal nanoparticles (NPs) strongly depend on their compositions and structures. Rational design of alloys and/or heterostructures provides additional approaches to modifying their surface geometric and electronic structures for optimized electrocatalytic performance. Here, a solution synthesis of freestanding intermetallic Au2 Bi NPs, the heterostructures of Au2 Bi/Bi hetero-NPs, and their promoted electrocatalytic CO2 reduction reaction (CO2 RR) performances were reported. It was revealed that the formation and in-situ conversion of heterogeneous seeds (e. g., Au) were of vital importance for the formation of intermetallic Au2 Bi and Au2 Bi/Bi hetero-NPs. It was also found that the Au components would act as the structure promoter moderating the binding strength for key intermediates on Bi surfaces. The alloying of Bi with Au and the formation of heterogeneous Au2 Bi/Bi interfaces would create more surface active sites with modulated electronic structures and stronger adsorption strengths for key intermediates, promoting the CO2 -to-HCOOH conversion with high activity and selectivity. This work presents a novel route for preparing intermetallic nanomaterials with modulated surface geometric/electric structures and promoting their electrocatalytic activities with alloying effects and interfacial effects. Such strategy may find wide application in catalyst design and synthesis for more electrocatalytic reactions.

8.
ACS Appl Mater Interfaces ; 14(8): 10648-10655, 2022 Mar 02.
Article in English | MEDLINE | ID: mdl-35167272

ABSTRACT

Electrochemical CO2 reduction reaction (CO2RR) yielding value-added chemicals provides a sustainable approach for renewable energy storage and conversion. Bismuth-based catalysts prove to be promising candidates for converting CO2 and water into formate but still suffer from poor selectivity and activity and/or sluggish kinetics. Here, we report that ultrathin porous Bi nanosheets (Bi-PNS) can be prepared through a controlled solvothermal protocol. Compared with smooth Bi nanoparticles (Bi-NPs), the ultrathin, rough, and porous Bi-PNS provide more active sites with higher intrinsic reactivities for CO2RR. Moreover, such high activity further increases the local pH in the vicinity of the catalyst surfaces during electrolysis and thus suppresses the competing hydrogen evolution reaction. As a result, the Bi-PNS exhibit significantly boosted CO2RR properties, showing a Faradaic efficiency of 95% with an effective current density of 45 mA cm-2 for formate evolution at the potential of -1.0 V versus reversible hydrogen electrode.

9.
Nanoscale ; 13(47): 20091-20097, 2021 Dec 13.
Article in English | MEDLINE | ID: mdl-34846444

ABSTRACT

The catalytic performances of metal nanoparticles can be widely tuned and promoted by the metal-support interactions. Here, we report that the morphologies and electrocatalytic CO2 reduction reaction (CO2RR) properties of bismuth nanoparticles (BiNPs) can be rationally modulated by their interactions with carbon black (CB) supports by controlling the degree of surface oxidation. Appropriately oxidized CB supports can provide sufficient oxygen-containing groups for anchoring BiNPs with tunable sizes and surface areas, desirable key intermediate adsorption abilities, appropriate surface wettability, and adequate electron transfer abilities. As a result, the optimized Bi/CB catalysts exhibited a promoted CO2RR performance with a Faradaic efficiency of 94% and a current density of 16.7 mA cm-2 for HCOO- at -0.9 V versus a reversible hydrogen electrode. Our results demonstrate the significance of regulating the interactions between supports and metal nanoparticles for both synthesis of the catalyst and electrolysis applications, which may find broader applicability in more electrocatalyst designs.

10.
ACS Appl Mater Interfaces ; 13(40): 47478-47487, 2021 Oct 13.
Article in English | MEDLINE | ID: mdl-34601863

ABSTRACT

Nanoporous graphenes (NPGs) have recently attracted huge attention owing to their designable structures and diverse properties. Many important properties of NPGs are determined by their structural regularity and homogeneity. The mass production of NPGs with periodic well-defined pore structures under a solvent-free green synthesis poses a great challenge and is largely unexplored. A facile synthetic strategy of NPGs via pressing organization calcination (POC) of readily available halogenated polycyclic aromatic hydrocarbons is developed. The gram-scale synthesized NPGs have ordered structures and possess well-defined nanopores, which can be easily exfoliated to few layers and oxidized in controllable approaches. After being decorated with oxygen species, the oxidized NPGs with tunable catalytic centers exhibit high activity, selectivity, and stability toward electrochemical hydrogen peroxide generation.

11.
Nat Commun ; 12(1): 2682, 2021 May 11.
Article in English | MEDLINE | ID: mdl-33976220

ABSTRACT

The demand for sustainable energy has motivated the development of artificial photosynthesis. Yet the catalyst and reaction interface designs for directly fixing permanent gases (e.g. CO2, O2, N2) into liquid fuels are still challenged by slow mass transfer and sluggish catalytic kinetics at the gas-liquid-solid boundary. Here, we report that gas-permeable metal-organic framework (MOF) membranes can modify the electronic structures and catalytic properties of metal single-atoms (SAs) to promote the diffusion, activation, and reduction of gas molecules (e.g. CO2, O2) and produce liquid fuels under visible light and mild conditions. With Ir SAs as active centers, the defect-engineered MOF (e.g. activated NH2-UiO-66) particles can reduce CO2 to HCOOH with an apparent quantum efficiency (AQE) of 2.51% at 420 nm on the gas-liquid-solid reaction interface. With promoted gas diffusion at the porous gas-solid interfaces, the gas-permeable SA/MOF membranes can directly convert humid CO2 gas into HCOOH with a near-unity selectivity and a significantly increased AQE of 15.76% at 420 nm. A similar strategy can be applied to the photocatalytic O2-to-H2O2 conversions, suggesting the wide applicability of our catalyst and reaction interface designs.

12.
Angew Chem Int Ed Engl ; 60(30): 16409-16415, 2021 Jul 19.
Article in English | MEDLINE | ID: mdl-33961317

ABSTRACT

2D conjugated MOFs have attracted significant interests in recent years owing to their special structural features and promising physical and chemical properties. These intriguing attributes, to a large extent, stem from the nature of incorporated ligands. The available ligands for the construction of 2D conjugated MOFs are still limited, especially those that have heteroatoms included and exposed to the pores. In this work, we designed and synthesized a highly symmetric hexaazatrinaphthylene (HATNA)-based ligand with two different coordination sites. Through selective coordination, a highly crystalline and porous 2D conjugated copper metal-organic framework was constructed. Due to the synergic effects of HATNA and copper catecholate node, this HATNA-based 2D conjugated MOF can mediate the electrocatalytic reduction of CO2 to methane with high selectivity of 78 % at high current density of 8.2 milliamperes per square centimetre (mA cm-2 ) for long durability over 12 hours.

13.
J Am Chem Soc ; 143(15): 5727-5736, 2021 Apr 21.
Article in English | MEDLINE | ID: mdl-33847495

ABSTRACT

Photocatalytic nitrogen fixation reaction can harvest the solar energy to convert the abundant but inert N2 into NH3. Here, utilizing metal-organic framework (MOF) membranes as the ideal assembly of nanoreactors to disperse and confine gold nanoparticles (AuNPs), we realize the direct plasmonic photocatalytic nitrogen fixation under ambient conditions. Upon visible irradiation, the hot electrons generated on the AuNPs can be directly injected into the N2 molecules adsorbed on Au surfaces. Such N2 molecules can be additionally activated by the strong but evanescently localized surface plasmon resonance field, resulting in a supralinear intensity dependence of the ammonia evolution rate with much higher apparent quantum efficiency and lower apparent activation energy under stronger irradiation. Moreover, the gas-permeable Au@MOF membranes, consisting of numerous interconnected nanoreactors, can ensure the dispersity and stability of AuNPs, further facilitate the mass transfer of N2 molecules and (hydrated) protons, and boost the plasmonic photocatalytic reactions at the designed gas-membrane-solution interface. As a result, an ammonia evolution rate of 18.9 mmol gAu-1 h-1 was achieved under visible light (>400 nm, 100 mW cm-2) with an apparent quantum efficiency of 1.54% at 520 nm.

14.
Nano Lett ; 19(10): 6819-6826, 2019 10 09.
Article in English | MEDLINE | ID: mdl-31498650

ABSTRACT

The electrochemical molecular intercalation of two-dimensional layered materials (2DLMs) produces stable and highly tunable superlattices between monolayer 2DLMs and self-assembled molecular layers. This process allows unprecedented flexibility in integrating highly distinct materials with atomic/molecular precision to produce a new generation of organic/inorganic superlattices with tunable chemical, electronic, and optical properties. To better understand the intercalation process, we developed an on-chip platform based on MoS2 model devices and used optical, electrochemical, and in situ electronic characterizations to resolve the intermediate stages during the intercalation process and monitor the evolution of the molecular superlattices. With sufficient charge injection, the organic cetyltrimethylammonium bromide (CTAB) intercalation induces the phase transition of MoS2 from semiconducting 2H phase to semimetallic 1T phase, resulting in a dramatic increase of electrical conductivity. Therefore, in situ monitoring the evolution of the device conductance reveals the electrochemical intercalation dynamics with an abrupt conductivity change, signifying the onset of the molecule intercalation. In contrast, the intercalation of tetraheptylammonium bromide (THAB), a branched molecule in a larger size, resulting in a much smaller number of charges injected to avoid the 2H to 1T phase transition. Our study demonstrates a powerful platform for in situ monitoring the molecular intercalation of many 2DLMs (MoS2, WSe2, ReS2, PdSe2, TiS2, and graphene) and systematically probing electronic, optical, and optoelectronic properties at the single-nanosheet level.

15.
Chem Commun (Camb) ; 55(72): 10705-10708, 2019 Sep 16.
Article in English | MEDLINE | ID: mdl-31429429

ABSTRACT

Electrocatalytic nitrogen reduction reactions (ENRR) can produce ammonia from nitrogen and water under ambient conditions. Here, we report the morphology-dependent electro-catalytic nitrogen reduction on Ag triangular nanoplates. Boosted by potassium cations, Ag triangular nanoplates with sharp edges exhibit a high faradaic efficiency of 25% with an ammonia yield of 58.5 mg gAg-1 h-1 at a low overpotential of -0.25 V vs. RHE. In comparison, rounded Ag nanoparticles mainly enclosed by {111} and {100} surfaces show a much smaller faradaic efficiency of 16% and ammonia yield of 38 mg gAg-1 h-1 at a larger overpotential (-0.35 V vs. RHE).

16.
Nanoscale ; 11(20): 10072-10079, 2019 May 28.
Article in English | MEDLINE | ID: mdl-31089635

ABSTRACT

Photocatalytic nitrogen fixation can produce ammonia from nitrogen and water under ambient conditions in the presence of sunlight. Here, we report that alkali metal cations (Li+, Na+, and K+) can significantly promote nitrogen activation and plasmonic nanocrystals (Au and Ag) can sensitize photocatalysts under visible light. The ammonia yield and selectivity on Au/P25 under UV-vis irradiation could be increased from 0.085 mmol g-1 h-1 and 75% to 0.43 mmol g-1 h-1 and 94.5% when promoted by K+, showing a visible-light-driven activity of 0.14 mmol g-1 h-1 and an AQE of 0.62% at 550 nm. The activity could be further increased to 1.02 (UV-vis) and 0.32 (visible) mmol g-1 h-1 with AQE of 0.93% at 550 nm with methanol added as the sacrificial agent. This strategy could be applied to a series of photocatalysts (e.g. TiO2, ZnO, and BiOBr) and may represent a general approach for designing efficient nitrogen fixation processes.

17.
Nat Commun ; 10(1): 2177, 2019 05 16.
Article in English | MEDLINE | ID: mdl-31097709

ABSTRACT

Air filtration has become an essential need for passive pollution control. However, most of the commercial air purifiers rely on dense fibrous filters, which have good particulate matter (PM) removal capability but poor biocidal effect. Here we present the photocatalytic bactericidal properties of a series of metal-organic frameworks (MOFs) and their potentials in air pollution control and personal protection. Specifically, a zinc-imidazolate MOF (ZIF-8) exhibits almost complete inactivation of Escherichia coli (E. coli) (>99.9999% inactivation efficiency) in saline within 2 h of simulated solar irradiation. Mechanistic studies indicate that photoelectrons trapped at Zn+ centers within ZIF-8 via ligand to metal charge transfer (LMCT) are responsible for oxygen-reduction related reactive oxygen species (ROS) production, which is the dominant disinfection mechanism. Air filters fabricated from ZIF-8 show remarkable performance for integrated pollution control, with >99.99% photocatalytic killing efficiency against airborne bacteria in 30 min and 97% PM removal. This work may shed light on designing new porous solids with photocatalytic antibiotic capability for public health protection.


Subject(s)
Air Filters , Disinfection/methods , Escherichia coli/drug effects , Metal-Organic Frameworks/pharmacology , Air Microbiology , Catalysis/radiation effects , Imidazoles/chemistry , Imidazoles/pharmacology , Light , Metal-Organic Frameworks/chemistry , Metal-Organic Frameworks/radiation effects , Microbial Sensitivity Tests , Oxygen/metabolism , Porosity , Reactive Oxygen Species/pharmacology , X-Ray Diffraction , Zinc/chemistry , Zinc/pharmacology
18.
Angew Chem Int Ed Engl ; 58(13): 4221-4226, 2019 Mar 22.
Article in English | MEDLINE | ID: mdl-30694606

ABSTRACT

Conjugated microporous polymers (CMPs) have full access to the organic synthesis toolbox and feature-rich functionality, structural diversity, and high surface area. We incorporated ferrocene (Fc) into the backbones of CMPs and systematically engineered their optical energy gaps. Compared with the CMPs without Fc units yet adopting a similar molecular orbital level, Fc-based CMPs can sufficiently generate reactive oxygen species (ROS) under visible light. The resultant ROS are able to effectively decompose the absorbed pollutants, including organic dyes and chemical warfare agents. Specifically, Fc-based CMPs significantly outperform commercial TiO2 (P25) in the degradation of methylene blue and are capable of converting 2-chloroethyl ethyl sulfide (a mustard gas simulant) into a completely nontoxic product.

19.
Research (Wash D C) ; 2019: 8304824, 2019.
Article in English | MEDLINE | ID: mdl-31922140

ABSTRACT

Direct far-field visualization and characterization of surface plasmon polaritons (SPPs) are of great importance for fundamental studies and technological applications. To probe the evanescently confined plasmon fields, one usually requires advanced near-field techniques, which is typically not applicable for real-time, high-throughput detecting or mapping of SPPs in complicated environments. Here, we report the utilization of rare-earth-doped nanoparticles to quantitatively upconvert invisible, evanescently confined SPPs into visible photoluminescence emissions for direct far-field visualization of SPPs in a complicated environment. The observed interference fringes between the SPPs and the coherent incident light at the metal surface provide a quantitative measurement of the SPP wavelength and the SPP propagating length and the local dielectric environments. It thus creates a new signaling pathway to sensitively transduce the local dielectric environment change into interference periodicity variation, enabling a new design of directly measurable, spectrometer-free optical rulers for rapid, ultrasensitive label-free detection of various biomolecules, including streptavidin and prostate-specific antigen, down to the femtomolar level.

20.
Angew Chem Int Ed Engl ; 57(50): 16416-16420, 2018 Dec 10.
Article in English | MEDLINE | ID: mdl-30328235

ABSTRACT

We present an iron-containing metal-organic framework, MIL-100(Fe), for ozone removal. MIL-100(Fe) exhibits long-lasting ozone conversion efficiency of 100 % for over 100 h under a relative humidity of 45 % and space velocity of 1.9×105  h-1 at room temperature, which is well beyond the performance of most porous or metal catalysts such as activated carbon and α-MnO2 . We also investigated the impact of humidity level and elucidated the plausible reaction mechanism, which is further confirmed by DFT calculations. Furthermore, MIL-100(Fe) can be processed into films and used as filtration layer in a mask to protect personnel against ozone contamination. This study demonstrates the promising potential of MOFs in ozone pollution control, and also offers new insights for the design of ozone decomposition catalysts.

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