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Incorporating open architectures into a self-assembled close-packed superstructure is vital to its component exposure and hence the overall performance presented. Here, we depict a high-yield, emulsion-based assembly strategy that enables the one-step organization of preformed nanocrystals into crystalline superparticles with tunable macroporosity. We show that tuning the water/hexane ratio and/or the shearing rate during the emulsification process allows a wide-range modulation of the size and density of macropores generated within SPs. In addition, we demonstrate that the evolution of macroporosity, having negligible influence on the long-range ordering of nanocrystals, benefits the fast mass transport and superior electrochemical performance in the subsequent demonstrations for lithium storage. In addition to the single-component nanocrystals, this assembly route is also applicable to the fabrication of macroporous binary nanocrystal SPs. [ABSTRACT FROM AUTHOR]

Fine-tuning the interfacial sites within heterogeneous catalysts is pivotal for unravelling the intricate structure-property relationship and optimizing their catalytic performance. Herein, a simple and versatile mixed-dimensional assembly approach is proposed to create nanocrystal-on-nanowire superstructures with precisely adjustable numbers of biphasic interfaces. This method leverages an efficient self-assembly process in which colloidal nanocrystals spontaneously organize onto Ag nanowires, driven by the solvophobic effect. Importantly, varying the ratio of the two components during assembly allows for accurate control over both the quantity and contact perimeter of biphasic interfaces. As a proof-of-concept demonstration, a series of Au-on-Ag superstructures with varying numbers of Au/Ag interfaces are constructed and employed as electrocatalysts for electrochemical CO2-to-CO conversion. Experimental results reveal a logarithmic linear relationship between catalytic activity and the number of Au/Ag interfaces per unit mass of Au-on-Ag superstructures. This work presents a straightforward approach for precise interface engineering, paving the way for systematic exploration of interface-dependent catalytic behaviors in heterogeneous catalysts., (© 2024 Wiley‐VCH GmbH.)

The industrialization of lithium-sulfur (Li-S) batteries faces challenges due to the shuttling effect of lithium polysulfides (LiPSs) and the growth of lithium dendrites. To address these issues, a simple and scalable method is proposed to synthesize 2D membranes comprising a single layer of cubic graphitic cages encased with few-layer, curved MoS 2 . The distinctive 2D architecture is achieved by confining the epitaxial growth of MoS 2 within the open cages of a 2D-ordered mesoporous graphitic framework (MGF), resulting in MoS 2 @MGF heterostructures with abundant sulfur vacancies. The experimental and theoretical studies establish that these MoS 2 @MGF membranes can act as a multifunctional interlayer in Li-S batteries to boost their comprehensive performance. The inclusion of the MoS 2 @MGF interlayer facilitates the trapping and conversion kinetics of LiPSs, preventing their shuttling effect, while simultaneously promoting uniform lithium deposition to inhibit dendrite growth. As a result, Li-S batteries with the MoS 2 @MGF interlayer exhibit high electrochemical performance even under high sulfur loading and lean electrolyte conditions. This work highlights the potential of designing advanced MoS 2 -encased heterostructures as interlayers, offering a viable solution to the current limitations plaguing Li-S batteries., (© 2024 Wiley‐VCH GmbH.)

Due to the precisely controllable size, shape, and composition, self-assembled nanocrystal superlattices exhibit unique collective properties and find wide applications in catalysis and energy conversion. Identifying their intrinsic electrocatalytic activity is challenging, as their averaged properties on ensembles can hardly be dissected from binders or additives. We here report the direct measurement of the oxygen evolution reaction at single superparticles self-assembled from ∼8 nm NiFe 2 O 4 and/or ∼4 nm Au nanocrystals using scanning electrochemical cell microscopy. Combined with coordinated scanning electron microscopy, it is found that the turnover frequency (TOF) estimated from single NiFe 2 O 4 superparticles at 1.92 V vs RHE ranges from 0.2 to 11 s -1 and is sensitive to size only when it is smaller than ∼800 nm in diameter. After the incorporation of Au nanocrystals, the TOF increases by ∼6-fold and levels off with further increasing Au content. Our study demonstrates the first direct single entity electrochemical study on individual nanocrystal superlattices with tunable structures and unravels the intrinsic structure-activity relationship that is not accessible by other methods.

Self-assembly of colloidal nanoparticles (NPs) into well-defined superstructures has been recognized as one of the most promising ways to fabricate rationally-designed functional materials for a variety of applications. Introducing hierarchical mesoporosity into NP superstructures will facilitate mass transport while simultaneously enhancing the accessibility of constituent NPs, which is of critical importance for widening their applications in catalysis and energy-related fields. Herein, we develop a colloidal co-assembly strategy to construct mesostructured, carbon-coated Co 0.5 Fe 2.5 O 4 NP superstructures (M-C@CFOSs), which show great promise as highly efficient electrocatalysts for the oxygen evolution reaction (OER). Specifically, organically-stabilized SiO 2 NPs are employed as both building blocks and sacrificial template, which co-assemble with Co 0.5 Fe 2.5 O 4 NPs to afford binary NP superstructures through a solvent drying process. M-C@CFOSs are obtainable after in situ ligand carbonization followed by the selective removal of SiO 2 NPs. The hierarchical mesoporous structure of M-C@CFOSs, combined with the conformal graphitic carbon coating derived from the native organic ligands, significantly improves their electrocatalytic performance as OER electrocatalysts when compared with nonporous Co 0.5 Fe 2.5 O 4 NP superstructures. This work establishes a new and facile approach for designing NP superstructures with hierarchical mesoporosity, which may find wide applications in energy storage and conversion., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)