Defect Sites Research Articles

Synthesis of Blue-Light Emitting Ag-Ga-S Quantum Dots for LED Application

Quantum dots (QDs), semiconductor nanocrystals smaller than 10 nm, can have their energy gap (Eg) adjusted by size due to the quantum size effect. So far, binary chalcogenide QDs, such as CdSe and PbS, have been widely investigated for their applications to liquid crystal displays and light-emitting diodes (LEDs), because they exhibit sharp photoluminescence (PL) peak with high quantum yields (QYs) and the PL peak wavelength can be controllable with the QD size. However, the use of toxic heavy metals such as Cd and Pb in these QDs poses significant environmental and health risks. To address this, we have developed multinary QDs using less toxic materials, such as Ag-In-Ga-S (AIGS), which exhibit sharp band-edge emission tunable from 500 to 600 nm by adjusting the In/Ga ratio [1]. Surface coating with gallium sulfide (GaSx) shell enhanced the peak intensity of band-edge emission due to the removal of the surface defect sites. We also successfully prepared green-light-emitting QD-LEDs with the use of AIGS QDs [2]. In this study, we report the synthesis of blue-light emissive QDs with AgGaS2 semiconductor, the bulk Eg of which is 2.7 eV. The obtained QDs exhibited a band-edge PL peak with a narrow peak width. These AgGaS2 QDs have been successfully utilized in the fabrication of blue-light QD-LEDs.AgGaS2 QDs were synthesized by heating corresponding metal precursors and sulfur compounds in a mixture of oleylamine and 1-dodecanethiol. The resulting QDs were surface-coated with GaSx shell. TEM analysis revealed that spherical or polygonal nanoparticles with an average size of ca. 5 nm were formed. It was found from XRD measurements that the AgGaS2 QDs had a tetragonal crystal structure. Absorption spectra of AgGaS2 QDs were blue-shifted from ca. 460 nm to 450 nm with a decrease in the Ag/Ga ratio in the precursors. The obtained QDs exhibited a sharp band-edge PL peak at ca. 450 nm as well as a broader defect-site emission peak at longer wavelengths. The surface coating with GaSx shell to form core-shell-structured AgGaS2@GaSx QDs enhanced the band-edge PL peak, the peak width of which was 22nm. This was probably because the deposition of the GaSx shell eliminated surface defect sites acting as a non-radiative recombination site on AgGaS2 cores. QD-LEDs were fabricated with thus-obtained blue-emitting QDs as an electroluminescence layer. The resulting QD-LEDs exhibited a sharp electroluminescence peak at ca. 450 nm with an external quantum efficiency of 0.66%, demonstrating their potential in blue-light QD-LED applications.

Design of Spherical Hard Carbon Secondary Particles for Na-Ion Battery Anode Application

Recently, Na-ion rechargeable batteries have been successfully developed and launched as the main power sources of a few novel electric vehicles in China. An energy density of the mass-produced Farasis Energy Na-ion batteries have been announced as between 140 Wh/kg and 160 Wh/kg with the layered oxide cathode and hard carbon anode combination. Though the commercialization of the Na-ion batteries is highly remarkable owing to the cost-effectiveness and long lifespan, the energy density of the Na-ion batteries needs to be improved even further considering the current state-of-art advanced practical Li-ion batteries of ca. 300 Wh/kg.Development of a novel anode material can contribute to the energy density improvement. Hard carbons with random shapes, which have been employed as the main anode materials in the commercial Na-ion batteries, have demonstrated the specific capacity of 200 to 300 mAh/g based on the carbonized biomasses. To improve energy density, shape and microstructure of the hard carbons need to be carefully designed. On the one hand, random shapes are not highly desired to achieve high tap density. Instead, spherical shapes with uniform particle sizes are beneficial to increase tap density as well as the energy density [1]. On the other hand, the carbonaceous microstructure needs to be optimized because the Na is stored through various mechanisms with combinations of i) adsorption at the surface of open pores, ii) adsorption at defect sites of graphene sheets, iii) insertion between graphene layers, and iv) pore filling [2]. As such, design of spherical hard carbon with well-established microstructure can provide high energy density. In this work, spherical hard carbon in Figure 1 was prepared using carbon precursor material (polyacrylonitrile) and sacrificial polymer (poly(styrene-co-acrylonitrile)) dissolved in the cosolvent (N,N-dimethylformamide). Carbonaceous microstructures were modified using the chemical and physical approaches. The morphological, structural, and electrochemical characterizations will be presented at the conference.[1] Oh, H. J. et al., Chem. Eng. J. 454, 140252 (2023)[2] Chen, C. et al., Carbon Energy 4, 1133-1150 (2022)Figure 1. SEM image of spherical hard carbon Figure 1

The study on the preparation of mineralized recombinant humanized collagen type I composite by a two-step method and its performance for bone regeneration

Due to the limited sources of autologous and allogeneic bone grafts, recombinant humanized collagen (rhCol) has attracted wide attention owing to its high bioactivity, good water solubility, low immunogenicity, and no virus risk. Herein, we prepare the mineralized recombinant humanized collagen type I (MrhCol I) composite to alleviate the problems of low utilization rate and rapid degradation of rhCol and promote a higher ability for bone regeneration. Based on the water-soluble characteristic of rhCol, MrhCol I composite was prepared through in vitro mineralization utilizing the two-step method of precipitation-dialysis. MrhCol I composite confirmed the presence of hydroxyapatite with an element ratio of 1.67 for calcium to phosphorus, which was similar to that of natural bone. The stepwise degradation of composite was mainly caused by the release of collagen from unreacted collagen and collagen bonded with hydroxyapatite, respectively. After 4 weeks of degradation, the degradation rate of MrhCol I composite was 16.16 % compared to 4.95 % of hydroxyapatite. Meanwhile, the scanning electron microscopy images and infrared spectra showed that MrhCol I composite still contained collagen molecules. In addition, MrhCol I composite had an excellent ability to promote MC3T3-E1 cell proliferation and differentiation. After the material was implanted into the cranial defect site of rats, bone volume fraction (BV/TV) and bone mineral density (BMD) of composite were 16.90 % and 0.42 g/cc, which were higher than those in other groups. These results indicated that MrhCol I composite provided a novel bionic artificial bone material for treating clinical bone defects.

(Invited) ppb-Level NO2 Monitoring Using Lung-Inspired MOF on Graphene Hybrids Sensor

NO2 is associated with 1.8% of all cardiovascular mortality and even the progression of neurodegenerative diseases1. To safeguard against this threat, the WHO has defined a NO2 exposure limit at ~5 ppb in its Global Air Quality Guidelines2. Consequently, it is essential to continuously and accurately monitor NO2 at ppb levels to provide personalized pollutant data. Ideal NO2 sensors should fulfil specific requirements: the ability to detect ppb-level NO2 in real-time, simplicity in operation (without external thermal- or photo excitation), cost efficiency, and wearability (lightness and flexibility). However, conventional materials such as metal oxides, transition metal dichalcogenides, or carbon derivatives often fail to meet these criteria due to their low sensitivity, slow response/recovery time, and high operating temperature3.Metal-organic frameworks (MOFs), comprising inorganic building units coordinated with organic linkers, are compelling opportunities to develop highly sensitive gas sensors. With their customizable topology, exceptional surface area, and uniform nanopore distribution4, MOFs are becoming increasingly attractive for their use in electrical sensory platforms owing to superior gas adsorption and surface reaction capabilities. Specifically, the semiconducting Cu3HHTP2 MOF has shown superior sensitivity and selectivity toward NO2 due to its strong redox activity. Nevertheless, practical challenges remained with using MOFs for NO2 sensors, such as limited mass flow, fabricating technology, and flexibility.In this work, we propose the use of laser-induced graphene (LIG) as a suitable platform for growing Cu3HHTP2 MOF to facilitate real-time monitoring of ppb-level NO2. LIG, an emerging 3D macroporous material, can be produced via direct laser irradiation of various polymer substrates5. By combining Cu3HHTP2 and LIG (resulting in LIG@Cu3HHTP2), we have observed synergistic effects that are not achievable with MOF alone (Fig. 1-4). Firstly, the nanostructured MOFs synthesized on the LIG platform accelerated the mass transport of exposed gases, which is attributable to their hierarchical macro-/microporous architecture. Moreover, the expanded exposure surface area leveraged the intrinsic advantage of MOFs, characterized by their abundant open metal sites and edge ligands for molecular adsorption. The human lung is an excellent example of a hierarchical pore architecture, enabling rapid transport of gas molecules over a large surface area. The LIG@Cu3HHTP2 showcased one of the most rapid response/recovery times (16 s/15 s) and the lowest limit of detection (LoD, 0.168 ppb) amongst cutting-edge NO2 sensors operating at room temperature and atmospheric conditions (Fig. 5-8). In addition, the selectivity toward NO2 over interference gases was demonstrated as a result of charge carrier transfer and size discrimination effect of MOF (Fig. 9). Secondly, we authenticated a patterning strategy for solution-based MOF growth, addressing one of the pivotal challenges in fabricating MOF-based electronic devices (Fig. 4). The LIG provides plentiful defect sites and dangling hydroxyl functional groups, forming an optimal platform for MOF nucleation. Also, in terms of device fabrication, laser processing can enable rapid, energy-efficient programmable micropatterning. Lastly, whereas traditional MOF-based electronic devices have predominantly been restricted to rigid substrates, our approach enabled their integration onto flexible and lightweight substrates via formation on LIG (Fig. 10 and 11). The flexibility of the resultant sensor was evaluated through computational modelling and real cyclic bending tests, with resilience observed across 10,000 iterative bending cycles, even under a stringent 2.5 mm curvature radius.Consequently, we successfully developed a LIG@Cu3HHTP2 hybrid capable of monitoring NO2 at the ppb level in real-time. These results will inform the advancement of MOFtronics applications, currently confined to lab-scale explorations, facilitating their transition towards real-world implementation as high-efficiency sensors.This work was supported by the National Research Foundation of Korea (NRF) grants funded by the Ministry of Education (2020R1A6A1A03040516). A. Schneider, et al., Umweltbundesamt, 2018.WHO, Global Air Quality Guidelines, 2021.S. Kumar, et al., Mater. Sci. Semicond. Process., 104865, 2020.M. D. Allendorf, et al., Chem. Rev., 120, 2020.F. M. Vivaldi, et al., ACS Appl. Mater. Interfaces. 13(26), 2021. Figure 1

Highly Conductive Deformation-Free Reduced Graphene Oxide Fibers : Towards High-Performance Wearable Supercapacitors

Solution-processed graphene fiber has been introduced by a wet spinning process of liquid crystal (LC) graphene oxide because of its strong hydrogen bonding and self-assembled layered structures with nematic phases. Substantially, graphene oxide (GO) solidified with layered structures in a coagulation bath. The LC-spun GO fibers generally have highly stacked and layered structures and are uneven along the fiber axis. However, due to the insulating properties of GO fiber, a reduction process should be introduced for a practical approach. Following the chemical reduction process, the LC-spun GO fiber has abundant and irregular structural deformation on the core and shell in fiber due to significant volume shrinkage. It has poor electrical conductivity, low specific surface area, and weak mechanical properties for applying high-performance supercapacitors.Herein, we introduce deformation-free graphene fiber by extruding reduced graphene oxide (rGO) and GO hybridization. This is also used in the conventional wet spinning processes. The rGO-GO hybrid dope is a possible candidate for applying porous graphene fiber with high electrical conductivity, effective surface area, and proper mechanical strength. In addition, the rGO has high electrical conductivity with low defect sites. The fabrication method is based on modified Brodie method which generates quasi-defect-free reduced graphene oxide as introduced previous work. In particular, against LC-spun GO spinning, high-quality rGO-GO dope reveals that the rGO minimizes the self-assembly of GO and adjusts the imbibition ratio simultaneously for rapid dope solvent-coagulation exchange on extruding the graphene fiber. In addition, chemically stable rGO plays a role in a frame for supporting the fiber structure after the reduction process without the deformation of core and shell structures. Despite porous rGO-GO fiber, the significantly high circularity and effective porosity could enhance electrical conductivity (~654 S/cm, after drawing) and capacitance of supercapacitors. The graphene fiber can be applicable for wearable energy storage devices with high performance.

(Invited) Optimizing the Activity of Oxygen Reduction Reaction Via Structural Engineering of Support for Fe-N-C Electrocatalysts in Proton Exchange Membrane Fuel Cells

The scarcity and costliness of platinum group metals in PEMFC cathodes hinder commercialization. Despite the promise of Fe-N-Cs electrocatalysts as alternatives, their oxygen reduction reaction (ORR) performance falls short. To address this, two carbon support-structural engineering methods were devised. Firstly, defect adjustment in ZIF-NC carbon support, derived from zeolitic imidazolate frameworks, via CO2 activation. Secondly, introduction of mesopores into ZIF-NC using the block co-polymer soft-template method. Controlled degree of defect sites in supports enhance intrinsic activity of Fe-N4 by modifying electronic structure such as charge distribution and spin state. Mesopores aid mass transport, improving active site accessibility. Additionally, the curved surfaces and carbon edge sites generated by mesopores alter the geometric structure of Fe-N4, optimizing the adsorption energy of oxygen species. Support-structural engineered Fe-N-Cs electrocatalysts exhibit relatively outstanding ORR performance compared to pristine Fe-N-C. MEAs with these electrocatalysts exhibit impressive peak power densities, highlighting their high activity at the MEA level.

Pd-Based Metal-Support Heterostructure Catalyst for High Performance Electrocatalytic N2 Reduction Reaction

Electrocatalytic nitrogen (N2) reduction reaction (eNRR) is of great interest to produce the green ammonia (NH3). However, the competitive side reaction of hydrogen (H2) evolution reaction (HER) and slow proton-couple electron transfer (PCET) step still become a bottleneck where resulting in poor N2 selectivity and yield of NH3 production. The heterostructures of metal and boron nitride (BN) analogs have been computatively demonstrated and suggested as a potential eNRR catalyst to improve eNRR performance as both suppressing HER and accelerating PCET step. However, experimental demonstration is still challenging due to the complex synthetic method required to achieve a uniform and dense distribution of metal catalysts on the BN surface. Here, we present the facile and uniform formation of the Pd nanoparticles (NPs) on defective boron nitride (BN) using ultrafast radiative Joule-heating within short time (~0.5 s), which is the first-time demonstration on the BN family. Especially, thanks to the strong electronic metal-to-support interaction (EMSI) effect between the defect site of BN surface and Pd NPs, the electron-deficient state of Pd NPs facilitates the significant reduce of free energy during the PCET step which is beneficial to interact with N2 molecules. In particular, we observe that Pd NPs on defective BN support exhibit the high NH3 selectivity of 68% in the neutral aqueous electrolyte and 59% of NH3 selectivity and 53.3 µg/h/cm2 of NH3 yield rate in the acidic media, respectively, which are the highest values of the selectivity and NH3 yield rate among existing Pd-based eNRR catalysts.

Site-Selective Atomic Layer Deposition at TiO2 Defects Via Targeted Dehydration

Minority atomic arrangement (i.e. defects) on surfaces exhibit distinct reactivity which allows for selective surface chemistry exclusively at those sites. We present an atomic layer deposition (ALD)-based technique of site-selective ALD (SS-ALD) targeting undesirable defect sites. Defects on the TiO2 and other oxidized surfaces affect the electronic properties, interfaces, and performance of optoelectronic devices utilizing those interfaces. We present first principles calculations to predict the difference in hydration/hydroxylation of pristine TiO2 terraces and minority atomic configurations (i.e. “defects”) including step edges and oxygen vacancies. In situ ellipsometry reveals the nucleation behavior of the SS-ALD at process conditions precisely tuned for selective hydroxylation of surface defects. An island growth model for nucleation and atomic force microscopy (AFM) imaging are consistent with a site-selective growth mechanism that depends on defect density.

3T-VASP: fast ab-initio electrochemical reactor via multi-scale gradient energy minimization

Ab-initio methods such as density functional theory (DFT) is useful for fundamental atomistic-level study and is widely used across many scientific fields, including for the discovery of electrochemical reaction byproducts. However, many DFT steps may be needed to discover rare electrochemical reaction byproducts, which limits DFT’s scalability. In this work, we demonstrate that it is possible to generate many elementary electrochemical reaction byproducts in-silico using just a small number of ab-initio energy minimization steps if it is done in a multi-scale manner, such as via previously reported tiered tensor transform (3T) method. We first demonstrate the algorithm through a simple example of a complex floppy organic molecule passivator binding onto perovskite solar cell surface defect site. We then demonstrate more complex examples by generating hundreds of electrochemical reaction byproducts in lithium-ion battery liquid electrolyte (many are verified in previous experimental studies), with most trajectories completed within 50–100 DFT steps as opposed to more than 10,000 steps typically utilized in an ab-initio molecular dynamics trajectory. This approach requires no machine learning training data generation and can be directly applied on any new chemistries, making it suitable for ab-initio elementary chemical reaction byproduct investigation when temperature dependence is not required.

Structure Sensitivity and Catalyst Restructuring for CO2 Electro-Reduction on Copper

Cu is the most promising metal catalyst for CO2 electroreduction (CO2RR) to multi-carbon products, but the structure sensitivity of the reaction and the stability versus restructuring of the catalyst surface under reaction conditions are still controversial. Here, atomic scale simulations of surface energies and reaction pathway kinetics supported by experimental evidence unveil that CO2RR does not take place on perfect planar Cu(111) and Cu(100) surfaces but rather on steps or kinks defects, and that these planar surfaces tend to restructure in reaction conditions to the active stepped surfaces. By combining basin hopping global sampling and grand canonical density functional theory, we show that the extremely low CO coverage on (111) and (100) surfaces, originating from sluggish CO2 conversion and unfavorable CO binding, limits the ability of these surfaces to reduce CO2 to multi-carbon products. Steps and kinks at surfaces, despite the lack of decrease in C-C coupling barriers on these sites, exhibit a significant increase in activity arising from beneficial CO2 activation and higher CO coverage. Notably, the square motifs adjacent to defects, not the defects themselves, are the active sites for CO2RR via synergistic effect. In addition, the strong binding of CO on defective sites acts as a thermodynamic driving force for the restructuring of planar surfaces to active stepped terminations under reactive conditions. We evaluate these mechanisms against experiments of CO2RR on UHV-prepared ultraclean Cu surfaces. Overall, our findings highlight the structural sensitivity in steering CO2RR and elucidate the origin of in situ restructuring of Cu catalysts during the reaction. We furthermore feature that the active sites for CO2RR are created under reaction conditions.

Highly Selective Electroreduction of Carbon Dioxide Using Defect-Driven Catalysis.

The production of methanol from the electrochemical reduction of CO2 is a promising method of mitigating climate change while simultaneously producing a useful liquid fuel. In this study, we design self-assembled monolayers (SAMs) of thiols on metal and metal oxide electrodes that operate via cooperative catalysis between the thiolated surface sites and exposed electrode defect sites. This defect-driven mechanism enables the fabrication of SAM-modified ZnO electrodes that yield methanol with an extraordinarily high Faradaic efficiency of up to 92%. To understand the origin of this high selectivity, we study the effect of the chain length of the alkanethiols, different tail functional groups, and applied voltages on catalyst performance. These results combined with density functional theory calculations give a detailed atomic-level understanding of catalyst operation. Furthermore, the SAM linkage tolerates CO2 reduction conditions, and the catalyst's excellent selectivity for methanol remains high after 10 h of continuous conversion. Taken together, these findings with SAM-based electrodes convey a new and facile design strategy for the creation of highly selective CO2 reduction electrocatalysts.

Ion Beam Implantation of Graphite Felt for Redox Flow Batteries: Role of Defects Versus Nitrogen Groups

Vanadium flow batteries (VFBs) are a promising solution to the growing demand for large-scale energy storage [1] . A critical component of VFBs are the electrodes, commonly manufactured from highly porous, carbon materials [2] . Carbon-based electrodes have good conductivity, high surface area, and are low-cost, however, they often exhibit poor activity for the vanadium redox reactions. The reactivity of electrode materials is of great interest, with previous research on carbon felt ascribing enhanced electrode reaction kinetics to the presence of oxygen functional groups (OFGs), nitrogen functional groups (NFGs), and/or carbon defects [3–6].In this study, catalytic sites were introduced into graphite felt using ion beam implantation to probe the effectiveness of specific active sites for the VFB. Specifically, N2 +- and Ne+-ion implantation are used to investigate the influence of introducing both NFGs and carbon defects versus carbon defects only. Polarisation curves and impedance measurements revealed that defects and edges sites introduced onto the electrode surface appear to be the relevant catalytic sites for facilitating the positive vanadium redox reaction. Raman spectroscopy and XPS helped to establish correlations between the surface chemistry and structure of graphite felt to electrode activity. Lower implantation fluences (< 1016 ion cm-2) were found to improve performance compared to pristine electrodes. In contrast, implantation at higher fluences resulted in the formation of amorphous carbon at the electrode surface, which was thought to result in a lower density of active defect sites and lower conductivity. Furthermore, this electrode modification technique was investigated on a scaled-up electrode geometry to assess its effectiveness for larger electrodes. Full- and half-cell measurements allowed for full-cell, positive half-cell, and negative half-cell performance to be independently investigated, whilst providing insight into performance-limiting factors. References K. Lourenssen, J. Williams, F. Ahmadpour, R. Clemmer, S. Tasnim. Vanadium redox flow batteries: A comprehensive review. J. Energy Storage 25 (2019) 100844.M.-S. Park, J. Ho Kim, M. Skyllas-Kazacos, K. Jae Kim, Y.-J. Kim. A technology review of electrodes and reaction mechanisms in vanadium redox flow batteries. J. Mater. Chem. A 3 (2015) 16913–16933.M. E. Lee, H.-J. Jin, Y. S. Yun. Synergistic catalytic effects of oxygen and nitrogen functional groups on active carbon electrodes for all-vanadium redox flow batteries. RSC Adv. 7 (2017) 43227–43232.L. Zeng, T. Zhao, L. Wei. Revealing the Performance Enhancement of Oxygenated Carbonaceous Materials for Vanadium Redox Flow Batteries: Functional Groups or Specific Surface Area? Adv. Sustainable Syst. 2 (2018) 1700148.H. Radinger, A. Ghamlouche, H. Ehrenberg, F. Scheiba. Origin of the catalytic activity at graphite electrodes in vanadium flow batteries. J. Mater. Chem. A 9 (2021) 18280–18293.S. C. Kim, J. Paick, J. S. Yi, D. Lee. Marked importance of surface defects rather than oxygen functionalities of carbon electrodes for the intrinsic vanadium redox kinetics in flow batteries. J. Power Sources 520 (2022) 230813.

Microenvironment-optimized gastrodin-functionalized scaffolds orchestrate asymmetric division of recruited stem cells in endogenous bone regeneration

The regeneration of osteoporotic bone defects remains challenging as the critical stem cell function is impaired by inflammatory microenvironment. Synthetic materials that intrinsically direct osteo-differentiation versus self-renewal of recruited stem cell represent a promising alternative strategy for endogenous bone formation. Therefore, a microenvironmentally optimized polyurethane (PU) /n-HA scaffold to enable sustained delivery of gastrodin is engineered to study its effect on the osteogenic fate of stem cells. It exhibited interconnected porous networks and an elevated sequential gastrodin release pattern to match immune-osteo cascade concurrent with progressive degradation of materials. In a critical-sized femur defect model of osteoporotic rat, 5% gastrodin-PU/n-HA potently promoted neo-bone regeneration by facilitating M2 macrophage polarization and CD146+ host stem cell recruitment to defective site. The implantation time-dependently increased the bone marrow mesenchymal stem cell (BMSC) population, and further culture of BMSCs showed a robust ability of proliferation, migration, and mitochondrial resurgence. Of note, some of cell pairs produced one stemness daughter cell while the other committed to osteogenic lineage in an asymmetric cell division (ACD) manner, and a much more compelling ACD response was triggered when 5% gastrodin-PU/n-HA implanted. Further investigation revealed that one-sided concentrated presentation of aPKC and β-catenin in dividing cells effectively induced asymmetric distribution, which polarized aPKC biased the response of the daughter cells to Wnt signal. The asymmetric cell division in skeletal stem cells (SSCs) was mechanically comparable to BMSCs and also governed by distinct aPKC and β-catenin biases. Concomitantly, delayed bone loss adjacent to the implant partly alleviated development of osteoporosis. In conclusion, our findings provide insight into the regulation of macrophage polarization combined with osteogenic commitment of recruited stem cells in an ACD manner, advancing scaffold design strategy for endogenous bone regeneration.Graphical abstract

Multifunctional Molecule Passivated Quasi‐2D Perovskite Film for Efficient and Stable Luminescent Solar Concentrator

AbstractQuasi−2D perovskite films with multiple quantum well structures can provide a large Stokes shift and efficient photoluminescence (PL), which have great potential in the application of luminescent solar concentrators (LSCs). However, its low photoelectric conversion efficiency and poor stability remain obstacles to commercial application. Here, a multifunctional molecule additive octyltriphenylphosphonium bromide is introduced to prepare high‐quality perovskite LSCs. The multifunctional molecule can simultaneously passivate perovskite cations and anions, reducing the defect sites and improving the photoluminescence quantum yield (PLQY) of the perovskite nanocrystals. Triphenylphosphine groups with high steric hindrance effect can hinder ion migration; the hydrophobic properties of the long alkyl chain prevent water erosion, which together improves the stability of the perovskite films. The multifunctional molecule passivated perovskite film has a high PLQY of 100% and retains 96% of the initial PL intensity after 30 days of indoor storage. The perovskite LSC device achieves a maximum optical efficiency of 6.5% at a geometric factor of 3.1. The findings open a new way to boost the performance of perovskite‐based LSCs.

Design of Ligand‐Nonbridging Sites in Metal–Organic Frameworks for Boosting Lithium Storage Capacity

AbstractMetal–organic frameworks (MOFs) are lagging in the use of lithium‐ion batteries (LIBs), ascribing to full coordination between metal nodes and organic ligands, to a large extent. By integrating a modulator into a ligand with missing bridging functionality, this study elucidates the role of non‐bridging defect sites in MOFs in tailoring lithium storage performance. A fully bridged pristine MOF (p‐MOF) utilizing the meso‐tetra(4‐carboxylphenyl) porphyrin ligand is compared with a modified MOF containing non‐bridging defects (d‐MOF) introduced by a homologous ligand, tris(4‐carboxyphenyl) porphyrin. Spectroscopic and cryogenic low‐dose electron microscopy techniques verify the presence of non‐bridging defect sites in the d‐MOF and reveal their explicit local structure. Density functional theory calculations show significantly enhanced Li+ adsorption energies and reduced Li+ migration barriers at the non‐bridging sites in the d‐MOF compared to the fully bridging sites in the p‐MOF. As a result, the d‐MOF exhibits exceptional lithium storage performance, achieving a high capacity of 761 mAh g−1 at 0.05 A g−1 and superior rate performance of 203 mAh g−1 at 5 A g−1, which substantially outperform the p‐MOF. This study highlights the potential of modulating MOFs with non‐bridging defects to develop high‐performance LIBs.

Efficient ozone decomposition by optimizing defect sites of NiMn-layered double hydroxides under high humidity air

Ozone is a pollutant that is very harmful to the ecological environment and human health, and layered double hydroxides (LDHs) have attracted much attention in recent years as an excellent anti-aqueous ozone catalyst. A kind of NiMn-LDHs with high defective sites was prepared by a one-step hydrothermal method to catalyze the degradation of ozone. The catalytic activity of NiMn-LDHs against ozone was further enhanced by increasing the concentration of oxygen vacancies on the surface while ensuring the intact structure of LDHs. When Ni/Mn=6:1, the catalyst had the best catalytic performance as well as stability, with 99.3 % degradation efficiency for 50 ppm ozone after 24 h of operation at WHSV=400000 mL·g−1·h−1 and RH=60 %. A series of data show that Ni6Mn-LDHs forms a crystal structure with lower crystallinity, larger specific surface area and smaller grain size. Compared with Ni2Mn-LDHs, the specific surface area of Ni6Mn-LDHs increased from 32.2 m2·g−1 to 171.4 m2·g−1, which is favourable to expose more surface defects. XPS and EPR confirmed that Ni6Mn-LDHs exhibited more surface oxygen vacancies, which plays a key role in the ozone decomposition process. The present study provides important guidance for the developed gaseous ozonolysis catalysts and promotes the practical ozone degradation performance of LDHs.

Design of Ligand-Nonbridging Sites in Metal-Organic Frameworks for Boosting Lithium Storage Capacity.

Metal-organic frameworks (MOFs) are lagging in the use of lithium-ion batteries (LIBs), ascribing to full coordination between metal nodes and organic ligands, to a large extent. By integrating a modulator into a ligand with missing bridging functionality, this study elucidates the role of non-bridging defect sites in MOFs in tailoring lithium storage performance. A fully bridged pristine MOF (p-MOF) utilizing the meso-tetra(4-carboxylphenyl) porphyrin ligand is compared with a modified MOF containing non-bridging defects (d-MOF) introduced by a homologous ligand, tris(4-carboxyphenyl) porphyrin. Spectroscopic and cryogenic low-dose electron microscopy techniques verify the presence of non-bridging defect sites in the d-MOF and reveal their explicit local structure. Density functional theory calculations show significantly enhanced Li+ adsorption energies and reduced Li+ migration barriers at the non-bridging sites in the d-MOF compared to the fully bridging sites in the p-MOF. As a result, the d-MOF exhibits exceptional lithium storage performance, achieving a high capacity of 761 mAh g-1 at 0.05 A g-1 and superior rate performance of 203 mAh g-1 at 5 A g-1, which substantially outperform the p-MOF. This study highlights the potential of modulating MOFs with non-bridging defects to develop high-performance LIBs.

Trimetallic FeNiCu Atomic Clusters Supported on Carbon Matrix: Highly Active Catalysts for C3H6-SCR of NO.

C3H6-SCR denitrification technology faces catalyst deactivation problems and low catalytic performance at medium-low temperatures. This study utilized the intermetallic synergies to prepare atomic cluster catalysts (FeNiCu/NC) by anchoring Fe-Ni-Cu on a carbon matrix to enhance the C3H6-SCR performance at medium-low temperatures. The synergistic effect of the Fe-Ni-Cu is reflected in the differences in the physicochemical properties of the catalysts, which is proved by several characterization techniques. Results showed that the FeNiCu/NC catalyst had a larger surface area (541.4 m2/g) and there were no metal oxides on the surface of the catalyst but abundant defective sites that anchored Fe/Ni/Cu atoms through N atoms to form M-Nx active sites and atomic clusters. The hollow carbon morphology provides sufficient active sites for C3H6-SCR. The coordination environments of active sites were M-Nx-C, Fe2/FeCu2/FeNi2, Ni3/NiFe/NiCu2, and Cu4/CuFe2/CuNi2, where the synergistic action of trimetal leads to the presence of Fe-Ni-Cu-Nx-C. The synergistic action of the Fe-Ni-Cu significantly improved the C3H6-SCR performance at medium-low temperatures. The FeNiCu/NC exhibited an 81% NO conversion at 150 °C under 2% O2, 15% and 20% higher than FeNi/NC and FeCu/NC catalysts, respectively. Even at 4% O2, the FeNiCu/NC catalyst was active to remove 78% NO and achieve a 93% N2 selectivity at 150 °C and maintained a 100% NO conversion at 300-425 °C. The DRIFTS results demonstrated that NO and C3H6 could combine with active O at metal cluster, M-Nx, or defective oxygen sites to produce various intermediate species, wherein acetates and nitrates were the main active intermediates. Based on the DRIFTS results, a reaction pathway for C3H6-SCR over the FeNiCu/NC catalyst was proposed.

Effect of calcination temperature on CeO2-based catalysts with enhanced photocatalytic degradation of phenol under UV light

This research delves into the photocatalytic degradation of phenol using CeO2 nanoparticles synthesized through solution combustion synthesis (SCS) at varying calcination temperatures (250, 300, 400, 500, and 600 °C). A comprehensive array of characterization techniques was employed, including XRD, FTIR, SEM-EDS, HR-TEM, N2 physisorption, UV–Vis DRS, Raman spectroscopy, and XPS. Our findings reveal a profound influence of calcination temperatures on the presence and quantity of Ce3+ and Ce4+ species, thereby modulating defective sites and surface area, crucial factors impacting performance. CeO2 synthesized at 400 °C stands out with a notable combination of high defects, extensive surface area, and a photocatalytic efficiency of 62 %. This work enhances our understanding of CeO2 photocatalysts for environmental applications and emphasizes the superior performance of mild calcination temperatures in ceria materials.

6-Trifluoromethylnicotinamide Bilaterally Anchored All Cations Implementing Efficient and Humidity-Stable Perovskite Solar Cells.

For organic-inorganic hybrid perovskite solar cells (PSCs), the volatilization of organic components and the presence of undercoordinated Pb2+ ions are the primary causes of device stability imbalance. These factors also serve as significant determinants that restrict the commercialization scale of PSCs. Here, 6-trifluoromethylnicotinamide (TNA) molecules, featuring amide and trifluoromethyl groups at both ends, were introduced as Lewis additives into the precursor solution of perovskite to anchor all cation defect sites and optimize the crystallization process of perovskite. Theoretical calculations confirmed that the -NH2 and C═O groups within the amide group on one side of the TNA molecule synergistically passivated the undercoordinated Pb2+ ions, whereas the trifluoromethyl group on the other side formed hydrogen bonds with the organic components of perovskite. The scorpion-like bilateral all-cation anchoring ability of TNA molecules was further substantiated through experimental characterization. Upon optimization of the TNA treatment concentration, a perovskite film characterized by large grains and a reduced defect density of states was achieved. The photovoltaic performance of PSCs incorporating TNA exhibited significant enhancement with an increase in efficiency from 22.42% (Control) to 24.15%. Under a harsh high-humidity environment, the comprehensive cation passivation effect of TNA significantly hindered the decomposition and phase transition of perovskite films, thereby ensuring excellent humidity stability for the PSCs.