Latest ArticlesCatalysts can significantly promote the reaction dynamics and are therefore considered crucial components for achieving high electrochemical energy conversion efficiency. However, the active sites of the catalysts, particularly for nano-level and atomic-level catalysts commonly undergo reconstruction under practical applications. Therefore, obtaining an in-depth and systematic understanding on the real active sites through in situ/operando characterization techniques is a prerequisite for establishing the structure-performance relationship and guiding the future design of more efficient electrocatalysts. Herein, we summarize the recent progress of in situ/operando characterization techniques for identifying the nature of active sites of electrocatalysts when used in electrocatalytic energy conversion reaction. Specifically, our focus lies in the fundamental principles of various in situ/operando characterization techniques, with particular emphasis on their applications for electrocatalytic reactions. Beyond that, the challenges and perspective insights are also added in the final section to highlight the future direction of this important field.
Natural enzymes, such as horseradish peroxidase (HRP), are a class of important biocatalysts with the high specificity, but their catalytic efficiency is usually unsatisfactory. Thus, the higher catalytic efficiency induced by the confinement effect is promising in optical sensing systems. In this work, a dark-field light scattering sensing platform was fabricated by the confinement effect of HRP from hybridization chain reaction (HCR) and then released to solution by the toehold-mediated strand displacement reaction (TSDR). Then, HRP catalyzed the 3,3′, 5,5′-tetramethylbenzidine (TMB) to TMB2+ with the assistance of hydrogen peroxide, which etched the gold nanorods (AuNRs) with the weakened light scattering. The single-particle assay was established based on the decreased light scattering intensity of AuNRs under dark-field microscope. The proposed assay revealed excellent analytical performance within a linear range from 25 pmol/L to 600 pmol/L, and a low limit of detection of 3.12 pmol/L. Additionally, it also manifested satisfactory recovery of miRNA-21 in human serum samples. The high sensitivity, excellent specificity, and universal applicability make this sensing platform promising for disease diagnosis.
Aqueous zinc ion batteries (AZIBs) are promising energy storage devices. However, the formation of dendrites, hydrogen evolution, and corrosion reaction seriously affect their electrochemical performance. Herein, the synergistic effect of ion-migration regulation and interfacial engineering has been confirmed as the potential strategy by kaolin functionalized glass fiber separator (KL-GF) to alleviate these problems. The rapid and orderly Zn2+ migration was achieved to improve the transfer kinetics and induced uniform zinc deposition by more zinc-philic sites of KL-GF. Based on the interfacial engineering, the side reactions were effectively mitigated and crystal planes were regulated through KL-GF. The hydrophilicity of KL alleviated the corrosion and hydrogen evolution. Importantly, a preferential orientation of Zn (002) crystal plane by KL-GF was induced to further realize dendrite-free deposition by density functional theory (DFT) and X-ray diffraction (XRD) characterization. Hence, the Zn|KL-GF|MnO2 cell maintained a high discharge capacity of 96.8 mAh/g at 2 A/g after 1000 cycles. This work can provide guidance enabling high-performance zinc anode for AZIBs.
Structural colors originated from Mie scattering of dielectric spheres can be regulated by the coupling effect between them and substrates. Here a rapid visual identification method of silver ornaments was proposed by the coupling effect of ZnO spheres with them. Both simulation and experimental results proved that, by coupling with different metal substrates, the Mie resonance scattering peaks of ZnO spheres with dimeter of 700 nm showed different degrees of redshift, which lead to different structural color appeared when ZnO spheres deposited on different metal surfaces with a similar appearance. A red structural color was displayed on the surface of the real silver ornament and a yellow-green structural color was shown on the surface of the cupronickel ornament. This method is quite simple and low-cost because it only needs to spray the dispersion of ZnO spheres on the ornament surface. Due to the mild chemical properties of the ZnO, covering and erasing ZnO spheres on the surface of silver would not corrode the silver ornament. Finally, an atomizer method was used for portable and daily testing. This work opens new perspectives on the visual identification of silver.
Lung cancer is one of the most common malignant tumors with the fastest increase in the incidence rate and mortality. Even after maximum tumor resection assistance with a radiotherapy and chemotherapy combination, the recurrence of non-small cell lung cancer is still inevitable. In addition, low targeting efficiency and poor permeability of drug delivery systems strongly affect the therapeutic efficiency of anti-cancer drugs on non-small cell lung cancer. Here we designed a gemcitabine (GEM) loaded arginine-glycine-aspartic acid-cysteine (RGDc)-modified gold mineralization "hybrid nanozyme bomb" (RGTG) to overcome those obstacles. RGDc modification improved the active targeting of liposomes to the tumor tissues with the second near-infrared (NIR-II)-triggered gold-shell disruption and GEM release. The collapsed gold-shell particles with a smaller size could penetrate the tumor solid barrier and act as photothermal therapy (PTT) agents to improve PTT therapy and starvation therapy via generating gluconic acid and reactive oxygen species (ROS). Moreover, the resting reversal effect of gold particles on tumor fibroblasts can achieve accelerating tumor penetration of gold particles and GEM. Compared to monotherapy, RGTG showed significant improvement in tumor inhibition, with a tumor volume reduction of 83% compared to the control group, which provides a promising tumor treatment platform for non-small cell lung cancer (NSCLC).
Hypercrosslinked polymers (HCPs) with large surface areas, high intrinsic porosities and low production costs may be available platforms for iodine capture. However, the lack of iodine-philicity binding sites limits their adsorption capacity. Here we use vapor-phase postsynthetic amination strategy to introduce electron-donating amino groups into the prefabricated HCPs for enhancing their iodine capture performance. Through simple vapor-phase exposure, the halogen-containing HCPs can be grafted by amines through nucleophilic substitution toward chloro groups. Combining with the abundant amino groups and high porosities, the amino-functionalized porous polymers show substantially increased iodine adsorption capacity, about 221% as that of original one, accompanied by excellent recyclability. Mechanism investigations reveal the key roles of the electron-donor amino groups and π-conjugated benzene rings along with structure characteristics of porous polymer frameworks in iodine capture. Moreover, this vapor-phase amination strategy shows good generality and can be extended to various amines, e.g., ethylenediamine, 1,3-diaminopropane and diethylenetriamine. Our work proves that this simple vapor-phase postsynthetic functionalization strategy may be applied in other porous polymers with wide application prospects in adsorption, separation and storage.
In order to advance the commercialization of rechargeable Li-air batteries, it is of importance to explore cathode catalyst with efficient catalytic activity. Transition metal oxides have poor electrical conductivity, while cobalt phosphide has excellent electrical conductivity and large specific surface area. Nevertheless, its application in organic Li-air batteries has been much less studied, and the electrocatalytic activity desires to be further elevated. Here, CoP/Co2P heterojunction composite with higher polarity was fabricated. The discharge product of high-polarity CoP/Co2P had a new porous box-like morphology, which was easy to be decomposed and exposed more active sites. The highly polar CoP/Co2P heterostructure composite had homogeneous pores, the synergistic effect existed between CoP and Co2P, and the discharge product was porous box mixed with Li2O2 and LiOH, which made CoP/Co2P achieve high specific capacity of 14632 mAh/g and cycle stably 161 times when used as air electrode cathode catalyst. This work furnished a thought for the construction of cathode catalysts with efficient catalytic activity for Li-air batteries.
Controlling the shape and composition of Pt-based nanocrystals is essential to improve electrocatalytic performance. In this work, we have carefully investigated the evolution process of morphology and composition for Pt and Pt3M (M = Ni, Co) nanocrystals by hydrochloric acid (HCl) etching. As a result, only Pt3Ni nanocrystals successfully formed unsaturated step-like atoms on the surface and then constructed high-index facets (HIFs), while Pt and Pt3Co preserved a good octahedron shape. Density functional theory (DFT) calculation suggests that Cl− ions can be tightly adsorbed on the surface of Pt3Ni rather than other nanocrystals, which hinders the deposition of newly-reduced atoms and thus regulating the surface morphology. Besides, the etching of surface transitional metals further accelerates the formation of HIFs. Boosted by the active sites on the surface, HCl-Pt-Ni exhibited a ~10.8 and ~11.3 times higher oxygen reduction reaction (ORR) mass and specific activities than commercial Pt/C catalyst, and possessed a good durability after 10,000 cycles test. This work gives a deep insight into the design of high-performance Pt-based ORR catalysts.
Dynamic covalent imine reactions between 2′,3′-dimethoxy-[1,1′:4′, 1″-terphenyl]-3,3″,5,5″-tetracarbaldehyde (DMTT) and cyclohexanediamine, p-phenylenediamine, and benzidine, respectively, generate a porous organic cage (DMPOC) and two covalent organic frameworks (COFs), USTB-29, and USTB-30. DMPOC shows a [3 + 6] topological cage-like structure according to single crystal X-ray diffraction result. In contrast, both microcrystalline USTB-29 and USTB-30 exhibit two-dimensional monoporous structures in an eclipsed AA stacking style based on powder X-ray diffraction and theoretical simulations. In addition, DMPOC is capable of efficiently absorbing the iodine vapor with an outstanding uptake of 5.10 g/g, much higher than that of USTB-29 (3.07 g/g) and USTB-30 (3.16 g/g). Cage to COFs transformations have been realized from DMPOC to USTB-29 and USTB-30 via the imine bond exchange with slightly increased iodine vapor uptake. Mechanism investigations uncover that both nitrogen and oxygen atoms of POC and COFs contribute to iodine vapor capture due to the formation of charge transfer matter, and loose interaction introducing adaptive expanding voids of DMPOC is suggested to capture more iodine vapor than that of COFs with strong π-π interactions.
The composite polymer electrolyte has been obtained via incorporating LiCUST-701 (a new metal–organic rotaxane framework modified by Li+) into poly(ethylene oxide) (PEO) matrix and give a high ionic conductivity of 4.02 × 10−4 S/cm at 60 ℃. DFT calculations were used to visualize the possible diffusion pathway of Li+. The all-solid-state cell assembled with LiFePO4, composite polymer electrolyte and lithium metal foil delivered with excellent cycling capability and stability even under high current densities.
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