An efficient nitrogen fixation reaction is highly desirable for obtaining the essential chemicals and energy carriers but remains a challenge due to the strong nonpolar bonding and considerable ...activation barrier of the NN triple bond (bond energy 940.95 kJ mol−1). Using an appropriate nanostructured catalyst that strongly interacts with nitrogen could promote adsorption and activation, lowering the energy barrier of nitrogen fixation and thus resulting in a relatively mild reaction. In this article, the review of the recent progress in nanostructured catalytic materials for nitrogen fixation is presented, including a comprehensive introduction and discussion on the pathway and mechanism of nitrogen fixation reaction, the recent achievements of a variety of nanostructured catalysts, and the kinds of catalytic nitrogen fixation reactions they are used in. In addition, the challenges faced by the reaction, strategies of catalyst design, and outlooks for further improving the performance of nitrogen fixation are also highlighted.
Designing nanostructured catalysts and constructing catalysis systems for the highly desirable nitrogen fixation reaction have attracted increasing attention for the development of ammonia synthesis. This article reviews the recent achievements of reported catalysts and the catalytic reactions in nitrogen fixation. The key issues and opportunities facing present and future research are concluded and expected for designing efficient nitrogen fixation processes.
Abstract
Exploring photocatalysts to promote CO
2
photoreduction into solar fuels is of great significance. We develop TiO
2
/perovskite (CsPbBr
3
) S-scheme heterojunctions synthesized by a facile ...electrostatic-driven self-assembling approach. Density functional theory calculation combined with experimental studies proves the electron transfer from CsPbBr
3
quantum dots (QDs) to TiO
2
, resulting in the construction of internal electric field (IEF) directing from CsPbBr
3
to TiO
2
upon hybridization. The IEF drives the photoexcited electrons in TiO
2
to CsPbBr
3
upon light irradiation as revealed by in-situ X-ray photoelectron spectroscopy analysis, suggesting the formation of an S-scheme heterojunction in the TiO
2
/CsPbBr
3
nanohybrids which greatly promotes the separation of electron-hole pairs to foster efficient CO
2
photoreduction. The hybrid nanofibers unveil a higher CO
2
-reduction rate (9.02 μmol g
–1
h
–1
) comparing with pristine TiO
2
nanofibers (4.68 μmol g
–1
h
–1
). Isotope (
13
CO
2
) tracer results confirm that the reduction products originate from CO
2
source.
Solar‐driven reduction of dinitrogen (N2) to ammonia (NH3) is severely hampered by the kinetically complex and energetically challenging multielectron reaction. Oxygen vacancies (OVs) with abundant ...localized electrons on the surface of bismuth oxybromide‐based semiconductors are demonstrated to have the ability to capture and activate N2, providing an alternative pathway to overcome such limitations. However, bismuth oxybromide materials are susceptible to photocorrosion, and the surface OVs are easily oxidized and therefore lose their activities. For realistic photocatalytic N2 fixation, fabricating and enhancing the stability of sustainable OVs on semiconductors is indispensable. This study shows the first synthesis of self‐assembled 5 nm diameter Bi5O7Br nanotubes with strong nanotube structure, suitable absorption edge, and many exposed surface sites, which are favorable for furnishing sufficient visible light‐induced OVs to realize excellent and stable photoreduction of atmospheric N2 into NH3 in pure water. The NH3 generation rate is as high as 1.38 mmol h−1 g−1, accompanied by an apparent quantum efficiency over 2.3% at 420 nm. The results presented herein provide new insights into rational design and engineering for the creation of highly active catalysts with light‐switchable OVs toward efficient, stable, and sustainable visible light N2 fixation in mild conditions.
A facile wet chemical method for water‐assisted self‐assembly of 5 nm diameter Bi5O7Br nanotubes is reported. The obtained 5 nm Bi5O7Br‐NT is characterized with large surface area (>96 m2 g−1), suitable absorption edge, and sufficient surface oxygen vacancies of light switch. As a result, 5 nm Bi5O7Br‐NT delivers an excellent visible light driven photocatalytic N2 fixation performance with a NH3 generation rate of 1.38 mmol h−1 g−1 in pure water.
Abstract
Solar conversion of CO
2
into energy-rich products is one of the sustainable solutions to lessen the global energy shortage and environmental crisis. Pitifully, it is still challenging to ...attain reliable and affordable CO
2
conversion. Herein, we demonstrate a facile one-pot approach to design core-triple shell Mn, C-codoped ZnO hollow spheres as efficient photocatalysts for CO
2
reduction. The Mn ions, with switchable valence states, function as “ionized cocatalyst” to promote the CO
2
adsorption and light harvesting of the system. Besides, they can capture photogenerated electrons from the conduction band of ZnO and provide the electrons for CO
2
reduction. This process is continuous due to the switchable valence states of Mn ions. Benefiting from such unique features, the prepared photocatalysts demonstrated fairly good CO
2
conversion performance. This work is endeavoured to shed light on the role of ionized cocatalyst towards sustainable energy production.
Environmental issues caused by oily pollutants is one of the most severe challenges for the global ecosystem and public health. To develop the advanced membrane materials with superior antifouling ...property is urgently needed for highly efficient oily wastewater purification. In this study, an ultrathin polydopamine layer with a controllable thickness of ~90 nm was decorated onto a porous polyketone substrate via an extremely simple and scalable surface modification process. The ammonia initiator facilitated the ultrafine polydopamine nanoparticles (with its size about 30 nm) in-situ assembling. Benefiting from the ultrathin surface modification, the resultant polydopamine decorated polyketone (PDA-d-PK) membrane performed ultrahigh water permeance up to 11600 L m−2 h−1 bar−1. This membrane also exhibited a superior oily emulsions separation property with remarkably high permeance up to 8300–10600 L m−2 h−1 bar−1, and high rejection ratio more than 99.9% against various oily phases, including hexane, hexadecane, petroleum ether, and soybean oil. The hierarchical nanosphere-like polydopamine layer with superhydrophilicity/underwater superoleophobicity also endowed the PDA-d-PK membrane with an excellent antifouling performance against the oily emulsions containing surfactant, protein, and natural organic material. The PDA-d-PK membrane also featured a superior tolerance and durability under challenging conditions of salty, strong acid/alkali solutions, and a variety of organic solvents. This work provides an insight into the facile preparation of an ultrathin polydopamine membrane with simultaneous enhancement in separation and antifouling properties for highly-efficient oil-water emulsions separation.
•Micro/nanosphere-like polydopamine particles were assembled on a polyketone substrate.•The polydopamine layer could be finely tuned by the deposition time and ammonia content.•Underwater superoleophobicity and robust self-cleaning properties were obtained.•High water/emulsion flux, oil rejection, and antifouling property were achieved.
Polymeric membranes with porous structures have attracted significant attention across a wide range of research fields. Nonsolvent-induced phase separation (NIPS) generates pores during the phase ...separation of a polymer solution via the nonsolvent penetration. In this work, an aliphatic polyketone (PK) was employed as a polymer matrix for NIPS, and an alginate additive was doped into the solution to induce either an accelerated or inhibited solvent-nonsolvent exchange rate controlled by alginate mobility during phase separation. As a result, the pore size of PK membrane was controllable and a desirable water permeance was achieved. Furthermore, the alginate additive within the membrane matrix also improved hydrophilicity, which is favorable for water transport and oil-fouling resistance. The oil-in-water (O/W) emulsion separation performances of optimized membranes largely depended on their altered membrane pore structures and properties, indicating the effectiveness and feasibility of this approach for NIPS-derived polymeric membranes. Alginate-rendered control of phase separation may also be applicable for the fabrication of other polymeric membranes that require pore modifications.
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•Alginate additives controlled the formation of porous polyketone membranes.•In situ cross-linking of alginates could be realized during membrane fabrication.•Underwater oleophobicity of the membrane was improved.•The membrane showed promising results in separating oil-in-water emulsions.
Abstract
The precise construction of photocatalysts with diatomic sites that simultaneously foster light absorption and catalytic activity is a formidable challenge, as both processes follow distinct ...pathways. Herein, an electrostatically driven self-assembly approach is used, where phenanthroline is used to synthesize bifunctional LaNi sites within covalent organic framework. The La and Ni site acts as optically and catalytically active center for photocarriers generation and highly selective CO
2
-to-CO reduction, respectively. Theory calculations and in-situ characterization reveal the directional charge transfer between La-Ni double-atomic sites, leading to decreased reaction energy barriers of *COOH intermediate and enhanced CO
2
-to-CO conversion. As a result, without any additional photosensitizers, a 15.2 times enhancement of the CO
2
reduction rate (605.8 μmol·g
−1
·h
−1
) over that of a benchmark covalent organic framework colloid (39.9 μmol·g
−1
·h
−1
) and improved CO selectivity (98.2%) are achieved. This work presents a potential strategy for integrating optically and catalytically active centers to enhance photocatalytic CO
2
reduction.
Abstract
Photoreduction of CO
2
to fuels offers a promising strategy for managing the global carbon balance using renewable solar energy. But the decisive process of oriented photogenerated electron ...delivery presents a considerable challenge. Here, we report the construction of intermolecular cascaded π-conjugation channels for powering CO
2
photoreduction by modifying both intramolecular and intermolecular conjugation of conjugated polymers (CPs). This coordination of dual conjugation is firstly proved by theoretical calculations and transient spectroscopies, showcasing alkynyl-removed CPs blocking the delocalization of electrons and in turn delivering the localized electrons through the intermolecular cascaded channels to active sites. Therefore, the optimized CPs (N-CP-D) exhibiting CO evolution activity of 2247 μmol g
−1
h
−1
and revealing a remarkable enhancement of 138-times compared to unmodified CPs (N-CP-A).
In this work, Ag-based compound nanorods were molecularly synthesized followed by the incorporation into PA active layer through interfacial polymerization (IP) process. This strategy achieved the ...concurrent construction of molecular sieving architecture and tunable surface function, by precisely controlling the release of zero-dimensional Ag nanoparticles (AgNPs, ∼5 nm), via in situ decomposition of the pH-responsive compounds serving as sacrificial nanocapsules. Featuring favorable interactions and sizes, the released ultrafine AgNPs serves as a quasi-molecule-scale regulator to generate the thin-film nanocomposite (TFN) membrane with wrinkled surface microstructures and loose internal architecture, due to the adjusted diffusion rate of amine monomers toward the organic phase during IP, while endowing the resultant membrane with superior antifouling/anti-biofouling properties. The newly-developed AgNPs embedded PA (AgNPs@PA) TFN membrane exhibited a high water permeance of 10.4 L m−2 h−1 bar−1 (more than twice that of the pristine PA 4.5 L m−2 h−1 bar−1) with a rejection ratio of 97.7% for Na2SO4, performing a competitive desalination property among the state-of-the-art nanofiltration membranes. The proposed technique for tuning the membrane microstructure opens opportunities for developing high-performance nanofiltration membranes for energy-efficient water remediation and treatment applications.
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•The Ag NPs incorporated PA TFN membrane was fabricated via IP method.•The Ag NPs were released via in situ decomposing of Ag compound nanorods.•A wrinkled surface profile with high internal porosity structure was developed.•High water permeance (10.4 L m−2 h−1 bar−1) and high rejection (97.7%) were obtained.•High sustainability of anti-fouling/-biofouling properties was achieved.
Polyamide (PA) based thin-film composite (TFC) membranes experience a high degree of organic fouling due to their hydrophobic and rough membrane surfaces during forward osmosis (FO) process. In this ...study, an ultrathin silica layer was grown in situ on the PA surface to enhance the antifouling property of TFC membrane by silicification process. Surface characterization confirmed the development of a silica layer on the PA surface. The superhydrophilic surface of silica-deposited TFC membrane (contact angle of 20°) with 3 h silicification time (STFC-3h) displayed a 53% higher water flux than the pristine TFC membrane without significantly affecting the membrane selectivity. The silica-modified TFC FO membranes also exhibited excellent stability when subjected to long-term cross-flow shear stress rinsing using deionized (DI) water, including exposure to salty, acidic and basic solutions. Moreover, the fouling tests showed that STFC-3h membrane lost only 4.2%, 9.1% and 12.1% of its initial flux with bovine serum albumin (BSA), humic acid (HA) and sodium alginate (SA), respectively, which are considerably lower compared to the pristine TFC FO membrane where flux losses were 18.7%, 23.2% and 37.2%, respectively. The STFC-3h membrane also revealed higher flux recovery ratio (FRR) of 99.6%, 96.9% and 94.4% with BSA, HA and SA, respectively, after physical cleaning than the pristine membrane (91.4%, 88.7%, and 81.2%, respectively). Overall, the in situ formation of an ultrathin hydrophilic silica layer on the PA surface reported in this work shows that the TFC membrane's water flux and antifouling property could be improved without diminishing the membrane selectivity.
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•Silica nanoparticles were grown in situ on the PA layer surface of TFC membrane.•Silica layer improved membrane wettability and separation performance.•Silicification duration of 3 h was the optimal modification condition.•Silica-modified TFC membrane showed good antifouling property.
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