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Electrochemical reduction in aqueous graphene oxide (GO) dispersion has emerged as an alternative route to producing a reduced GO (rGO) membrane on Au mesh. Under scanning electron microscopy, an interesting pattern formed by distinct differences was discovered from the deoxidization evolution. Scanning transmission X-ray microscopy shows the chemical composition coordination mixing of C–OH, C–O–C, HO–C O, and C O bonds at nanoscale resolution. The electrochemical reduction of C–OH, new bonding of C–O–C, and structure recovery of C C were obtained from GO transformation into the rGO membrane. In Kelvin probe force microscopy, the same pattern of rGO was also observed for the diversity of work functions ranging from 5.55 to 5.70 eV compared with the uniform distribution of GO of 5.78 eV. Density functional theory calculations predicted that the work function variation originated from the dependence of O atom number and functional group species. A high (low) diversity in work function values was ascribed to the C–O–C (HO–C O) bond even with increasing oxygen numbers, accounting for the peak variation. Controlling the work function holds great significance for photovoltaic behavior and band alignment in photoelectric devices. Thus, growing large-area rGO membranes offers a new route to obtaining membranes for applications requiring transparent materials.

Direct probing of metal–oxygen chemistry at the solid/liquid interface is essential to unravel the reaction mechanism of metal–air batteries. Ambient pressure X-ray photoelectron spectroscopy (APXPS) is an effective tool to study metal–oxygen reactions but has been limited to solid-state environments. Here, for the first time, we demonstrate in situ probing of potassium oxygen reduction/evolution reaction (ORR/OER) via APXPS in ionic liquid-based air batteries. We reveal the formation and oxidation of K2O and K2O2 in K–O2 batteries, highlighting new reaction pathways in addition to the widely established one-electron process in K–O2 batteries. Importantly, we show that the formation and subsequent oxidation of K2O2 trigger irreversible cell chemistry, which could be responsible for capacity decay in K–O2 batteries. We further show that common impurities in air such as H2O and CO2 reduce chemical reversibility of ORR and OER. This study reveals root causes of irreversible cell chemistry in K–air batteries via direct probing of ionic liquid-based air batteries via APXPS, which can be widely applied to study the chemistry of solid/liquid interfaces of metal–air batteries.

We report temperature dependence of electrical conductivity and thermopower for poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) thin films post-treated using a combination of an...

Li1.5Al0.5Ge1.5(PO4)3 (LAGP) is a promising solid electrolyte for use in next-generation lithium batteries. Nevertheless, its lower bulk and grain-boundary ionic conductivities are major restrictions preventing its practical utilization. Mg was introduced into LAGP to form Li1.6Al0.4Mg0.1Ge1.5(PO4)3 (LAMGP) based on computational analysis. The doping of LAGP with Mg results in advantages such as increasing the Li+ concentration and expanding the material dimensions due to the larger ionic radius of Mg, leading to enhanced ionic conductivity. Mg had a two-birds-with-one-stone effect in the LAMGP electrolyte, not only generating super high bulk ionic conductivity of 7.435 mS cm−1, compared to 2.896 mS cm−1 in LAGP, but also generating low grain-boundary resistance due to improved densification. The lowering of the grain-boundary resistance and the increased densification are related to choosing the right precursor for the dopant. Using LAMGP as a hybrid solid electrolyte, a solid battery delivered great electrochemical performance in comparison to when LAGP was used. Interfacial analysis was also conducted, which revealed that the formation of an interface prevented the reduction of components in LAMGP by Li metal, therefore ensuring the long-term durability of LAMGP in liquid electrolyte. These results suggest that LAMGP is an auspicious solid electrolyte for achieving practical solid-state lithium batteries.

Lithium manganese oxide (LMO) is one of the most promising cathode materials for lithium-ion batteries. However, the dissolution of manganese and its deposition on the anode surface cause poor cycling stability. To alleviate these issues, a film composed of polyvinylidene difluoride (PVDF) and Li5.6Ga0.26La2.9Zr1.87Nb0.05O12 type garnet (PVDF@LGLZNO) is coated directly on the LMO electrode and it functions as a promising artificial cathode–electrolyte interphase (CEI). The film thickness is optimized taking into account the electrospinning–processing time. To realize a cell with good capacity retention, excellent rate capability and resilience under harsher conditions (e.g. elevated temperature or high rates), the coated LMO cathode is coupled with a new anode which consists of sulfurized carbon derived from polyacrylonitrile (S-C(PAN)). The electrode (LMO-30 min) coated with the PVDF@LGLZNO composite material shows outstanding cycling stability and rate capability, as well as capacity retention when compared to the bare electrode both at room temperature (25 °C) and elevated temperature (55 °C). The PVDF@LGLZNO fibrous film coating suppresses the dissolution of manganese both at high C-rates and 55 °C, as supported by XPS, whereas PVDF coated and bare LMO cathodes are not able to prevent further deterioration of themselves. The film significantly minimizes undesirable side reactions at the cathode–electrolyte interface and reduces charge transfer resistance. The new cell with PVDF@LGLZNO (LMO-30 min) modified cathode and S-C(PAN) anode delivers capacity retention of 77% after 1000 cycles at 1C, corresponding to an average capacity decay of 0.023% per cycle.

A hierarchically structured bimetallic nanocatalyst (NC) comprising a metallic Pd-nanocluster adjacent to local tetrahedral symmetric Ni-oxide and a thin layer of tetramethyl orthosilicate (TMOS) decoration (denoted as NiOTPd-T) is synthesized by sequential control of the metal ion adsorption followed by wet chemical reduction on a carbon nanotube support. By cross-referencing the results of the physical structure inspections, in situ ambient pressure X-ray photoelectron spectroscopy, and gas chromatography-mass spectrometer analysis, we demonstrate that the NiOTPd-T gains an optimum production yield of 1905.1 mmol g−1 of CH4 which is more than 10-fold improved as compared to that of TMOS decorated Pd nanocatalysts (Pd-T) at 573 K. Such an exceptional performance is attributed to the local synergetic collaboration between CO chemisorption on Pd atoms and H2 splitting on both the Pd and Ni atoms at the interface region. Once the collaboration is triggered, the subsequent NiOT reduction increases the number of metallic Ni sites. It further facilitates the H2 splitting, therefore optimizing the CH4 production yield of NiOTPd-T. Most importantly, to the best of our knowledge, with such a unique Pd-to-NiOT epitaxial structure, the NiOTPd-T catalysts exhibit the highest CH4 production yield among existing catalysts with the same loading and composition and of any geometric configuration.

The development of carbon materials as highly efficient and durable substrates for surface-enhanced Raman scattering (SERS) is of great importance for realizing practical application of molecular s...

This work demonstrates the first example of interfacial manipulation in a hybrid photocatalyst based on poly(3-hexylthiophene-2,5-diyl) (P3HT) nanoparticle and graphene oxide (GO) bulk heterojunctions to efficiently reduce CO2 into selective industrial hydrocarbons under gas-phase reaction and visible-light illumination. High selectivity of chemical products (methanol and acetaldehyde) was observed. Moreover, the hybrid photocatalyst’s solar-to-fuel conversion efficiency was 13.5 times higher than that of pure GO. The increased production yield stems from the co-catalytic and sensitizing role of P3HT in the hybrid system due to its ability to extend light absorption to the visible range and improve interfacial charge transfer to GO. The hybrid P3HT-GO formed a type II heterojunction, and its static and dynamic exciton behaviors were examined using fluorescence spectroscopy and exciton lifetime mapping. A reduced fluorescence decay time was observed by interfacial manipulation for improved dispersion, indicating a more efficient charge transfer from the excited P3HT to GO. Thus, the conducting polymer nanoparticles, 2D nanocarbon, have demonstrated superior performance as a metal-free, non-toxic, low-cost, and scalable heterogeneous photocatalyst for CO2 reduction to solar fuel, a solid–gas system.

Sulfurized polyacrylonitrile (S-cPAN) has been recognized as a particularly promising cathode material for lithium-sulfur (Li-S) batteries due to its ultra-stable cycling performance and high degree of sulfur utilization. Though the synthetic conditions and routes for modification of S-cPAN have been extensively studied, details of the molecular structure of S-cPAN remain yet unclear. Herein, a more reasonable molecular structure consisting of pyridinic/pyrrolic nitrogen (NPD/NPL) is proposed, based on the analysis of combined X-ray photoelectron spectroscopy, 13C/15N solid-state nuclear magnetic resonance, and density functional theory data. The coexistence of vicinal NPD/NPL entities plays a vital role in attracting S2 molecules and facilitating N-S bond formation apart from the generally accepted C-S bond in S-cPAN, which could explain the extraordinary electrochemical features of S-cPAN among various nitrogen-containing sulfurized polymers. This study provides new insights and a better understanding of structural details and relevant bond formation mechanisms in S-cPAN, providing a foundation for the design of new types of sulfurized cathode materials suitable for application in next-generation high-performance Li-S batteries.

Correction for ‘Local synergetic collaboration between Pd and local tetrahedral symmetric Ni oxide enables ultra-high-performance CO2 thermal methanation’ by Che Yan et al., J. Mater. Chem. A, 2020, 8, 12744–12756, DOI: 10.1039/D0TA02957B.

The combined effect of concentrated electrolyte and cycling protocol on the cyclic performance of the anode-free battery (AFB) is evaluated systematically. In situ deposition of Li in the AFB configuration in the presence of a concentrated electrolyte containing fluorine-donating salt and resting the deposit enables the formation of stable and uniform SEI. The SEI intercepts the undesirable side reaction between the deposit and solvent in the electrolyte and reduces electrolyte and Li consumption during cycling. The synergy between the laboratory-prepared concentrated 3 M LiFSI in the ester-based electrolyte and our resting protocol significantly enhanced cyclic performances of AFBs in comparison to the commercial carbonate-based dilute electrolyte, 1 M LiPF6. Benefitting from the combined effect, Cu∥LiFePO4 cells delivered excellent cyclic performance at 0.5 mA/cm2 with an average CE of up to 98.78%, retaining a reasonable discharge capacity after 100 cycles. Furthermore, the AFB can also be cycled at a high rate up to 1.0 mA/cm2 with a high average CE and retaining the encouraging discharge capacity after 100 cycles. The fast cycling and stable performance of these cells are attributed to the formation of robust, flexible, and tough F-rich conductive SEI on the surface of the in situ-deposited Li by benefiting from the combined effect of the resting protocol and the concentrated electrolyte. A condescending understanding of the mechanism of SEI formation and material choice could facilitate the development of AFBs as future advanced energy storage devices.

In-depth mechanistic understanding of CO2 reduction reaction (CRR) and CO2 evolution reaction (CER) is the prerequisite to develop stable and efficient Li–CO2 batteries. In this study, we investigate the redox reaction of CO2 on the porous carbon surface in ionic liquid electrolyte via synchrotron-based in situ ambient pressure X-ray photoelectron spectroscopy (APXPS) technique. We used ionic liquid to facilitate CO2 capture and stabilize CRR intermediate anions owing to its strong solvation for Li+. We demonstrate that pure CO2 reduction is not electrochemically active at room temperature on porous carbon electrode and its kinetics can be remarkably improved by H2O, which could be responsible for the discrepancy on CRR kinetics in the literature. However, in the presence of H2O, the formed LiOH gradually converted to Li2CO3 leading to severe electrolyte degradation in charging reaction. With the assistance of O2 in the ionic liquid-based electrolyte, we show, for the first time, CRR yields a low-valence amorphous carbon and Li2O2/Li2O in the Li–CO2 batteries. The formed amorphous carbon, Li2O2 and Li2O exhibit higher rechargeability and faster kinetics compared with Li2CO3-oxidation. These new findings provide direct evidence of CRR mechanism and insights in resolving the discrepancy on CRR kinetics in Li–CO2 batteries.

Ru–Pd nanoparticles (NPs) with Pt atomic cluster modification were synthesized using polyol reactions with a sequence design. Such modification resulted in the formation of Ru in the inner core and Pd on the outer shell structure (Rucore–Pdshell) via transmetalation between the Pt ion and Pd atom followed by thermal reduction. The Pt modified Rucore–Pdshell NPs improve the on-set potential by 0.041 volt and reduce Pt loading to less than ∼2%, as compared with that of carbon supported Pt NPs. For the optimum case, the MA (current degradation) of Ru–Pd NPs is improved (suppressed) by ∼345% (18.1%) in the accelerated degradation test (ADT) at 0.85 volt (vs. RHE) for 5000 cycles by intercalating Pt clusters (2 to 9 at%) in the NP surface. These improvements are attributed to the electron localization and reinforcement by surface Pt clusters, which facilitated the oxygen reduction activity and chemical durability of NPs.

The unregulated growth of lithium dendrite upon cycling is hampering the applications of lithium metal batteries. The inherent artificial solid electrolyte interphase (SEI) formed during the first few cycles cannot provide the desired stability of lithium deposition. In the anode free battery (AFB) configuration, uncontrolled lithium plating on bare copper imposes a more serious lithium dendrite growth. Herein, we modify the copper current collector with a binder-free ultra-thin spin-coated graphene oxide (GO). The synchronize smooth and conductive GO-coated artificial SEI with lithium fluoride derived from fluoroethylene carbonate (FEC) electrolyte additive greatly control the lithium deposition. Accordingly, the synergistic effect enables smooth, uniform, and dendrite-free lithium plating. Moreover, the AFB with GO film and 5% FEC in the carbonate-based electrolyte is capable of achieving high coulombic efficiency of an average 98% and attains ~44% of its initial capacity after 50 cycles. In contrast, the full cell with bare Cu//LiNi1/3Mn1/3Co1/3O2 (NMC) has a coulombic efficiency of 89% and retains 26.9% after 20 cycles. Our results demonstrate that the synergy of GO-coated artificial SEI with FEC additive can be a promising approach to impede lithium dendrites growth and result in enhanced electrochemical performance in an AFB.

The performance of lithium ion batteries rapidly falls at lower temperatures due to decreasing conductivity of electrolytes and solid electrolyte interphase (SEI) on graphite anode. Hence, it limits the practical use of lithium ion batteries at subzero temperatures and also affects the development of lithium ion batteries for widespread applications. The SEI formed on the graphite surface is very influential in determining the performance of the battery. Herein, a new electrolyte additive, 4-chloromethyl-1,3,2-dioxathiolane-2-oxide (CMDO), is prepared to improve the properties of commonly used electrolyte constituents-ethylene carbonate (EC), and fluoroethylene carbonate. The formation of an efficient passivation layer in propylene carbonate-based electrolyte for MCMB electrode was investigated. The addition of CMDO resulted in a much less irreversible capacity loss and induces thin SEI formation. However, the combination of the three additives played a key role to enhance reversible capacity of MCMB electrode at lower or ambient temperature. The electrochemical measurement analysis showed that the SEI formed from a mixture of the three additives gave better intercalation-deintercalation of lithium ions.

The formation of a high quality interface between metallic and organic semiconducting thin films is critically important in achieving high-performance organic electronics devices. In this regard, the importance of understanding the multifaceted issue of structure damage incurred to organic films by the evaporated metal atoms cannot be overstated. In the present study, we have investigated the change of a structurally ordered, organic semiconducting (o.s.) thin film of 5,11-bis(triethylsilylethynyl)anthradithiophene (TESADT) effected by gold atoms by means of synchrotron-based soft X-ray spectroscopies including ultraviolet photoemission spectroscopy (UPS) and X-ray photoemission spectroscopies (XPS) with imaging capability, near edge X-ray absorption fine structure (NEXAFS) spectroscopy, and atomic force microscopy (AFM). This work shows that gold atoms readily diffuse into the organic films and nucleate into nanometer-size clusters, damage chemical structure, destroy structural ordering of the organic fi...

Solvent–vapor annealing was used to increase the field-effect mobility of soluble triethylsilylethynyl anthradithiophene spin-coated on organosilane-terminated silicon dioxide, yielding a high value of 1.2 cm 2 V −1 s −1 . The cause of improvement was investigated by atomic force microscopy, X-ray diffraction, and near-edge X-ray absorption fine structure spectroscopy. Vapor annealing exerts little effect on the molecular tilt and the crystallinity normal to the surface, but improves the film morphology significantly, yielding larger grains with perhaps better in-plane crystallinity.

Cubic shells and spherical nanoparticles of β-SiC were produced at 1273 K by processing the ceramic precursors formed from the reactions between vapors of organochlorosilanes, Me 2 SiCl 2 , MeSiCl 3 , MeSiHCl 2 , and PhSiCl 3 , and liquid Na at 523-723 K. From Me 2 SiCl 2 , a flexible linear polycarbosilane precursor was synthesized and covered the NaCI byproduct surface to form a cubic shape. Hollow cubic β-SiC shells were produced after the NaCl templates were removed. From MeSiCl 3 , a rigid cross-linked polycarbosilane was produced and phase segregated from the NaCl byproduct. The precursor was transformed into nanoparticles without special morphology. MeSiHCl 2 produced a cross-linked polysilane precursor at low temperatures, which can be converted into a mixture of β-SiC and Si nanoparticles. At high temperatures, the polysilane converted to polycarbosilane and produced hollow cubic β-SiC shells. The carbon-rich PhSiCl 3 generated cube-like particles as the final product, which contained β-SiC and carbon.

Due to its special properties, amorphous carbon (a-C) materials have been reported to display novel functions for many potential optical [1,2], frictional [3] and electronic [2,4] applications. These include protective coating, ultra durable anti-reflection coatings [1,2], mechanical devices [2,3], and electron emitters [4]. The ability to fabricate a-C into desired physical shapes has attracted much attention. For example, anodic aluminum oxide (AAO) has been used as templates to shape a-C into tubular shapes by pyrolyzing propylene inside the AAO channels [5]. In our study herein we report on a process to grow a-C tubes (a-CT) by coupling two fabrication methods we recently developed [6,7]. First, a layer of short aligned a-CT was deposited by LPCVD from SiCl3CCl3 on an AAO substrate [6]. Then, by employing the Na-filled AAO (Na@AAO) reactive template method, we were able to significantly elongate the a-CT [7]. Using a hot-wall LPCVD reactor with a base pressure of 10 1 Pa, SiCl3CCl3 (Aldrich, 97%) was evaporated at 273 K without carrier gas. The precursor was decomposed at 1273 K and 10 Pa to deposit a layer of carbon on AAO substrates (Whatman Anodisc 13, observed pore diameter: 280 nm, thickness: 60 lm). After 3 h, the AAO substrates turned black and the product a-C film on AAO (a-C/AAO) was obtained. As shown by the scanning electron microscope (SEM, JEOL JSM-6330F at 15 kV) images in Fig. 1, the average diameter of the open-ended a-CT, 330–340 nm, is close to the channel diameter in the AAO. The average thickness of the a-CT wall was 30 nm. In Fig. 1(b), the average thickness of the array layer was estimated to be 800 nm, much thinner than the AAO thickness of 60 lm. We speculate that the activated species generated from SiCl3CCl3, :CCl2, cannot diffuse effectively into the AAO channels to form a thick carbon layer. Fig. 1(b) also shows that the a-CT array is connected as a layer of film on top of the AAO. Using energy dispersive spectroscopy (EDS), the composition of the isolated tube array layer was confirmed to be carbon. Thus, the data support the conclusion that we have successfully deposited a-C on AAO (a-C/AAO) in the form of short a-CT array. We also attempted to perform this process on a home-made AAO with a channel diameter of 30 nm. However, :CCl2 apparently could not diffuse into the narrow AAO channels to grow into an a-CT layer. After the short a-C/AAO layer was fabricated by LPCVD, we explored the possibility of extending the tube length by the sodium reactive template method that had been previously developed [6]. By decomposing NaH (Aldrich, 0.2 g, 8 mmol) on a-C/AAO inside a tube furnace at 623 K under 1 atm of Ar (flow rate: 30 sccm) for 0.5 h, Na filled the channels of AAO to generate Na@a-C/AAO. Further reaction of Na@a-C/AAO with Carbon 43 (2005) 2618–2641

Bimetallic nanostructured core-shell structures are commonly used as catalysts in a wide variety of reactions. We surmised that the addition of an additional metal would potentially allow catalytic tailoring with the possibility of an increase in activity. Here a tri-metallic catalytic structure, consisting of clustered catalytic Pt on the surface of a Pd shell supported on a rod shaped Au core was fabricated. The significance of the additional metallic component is shown by comparative electrochemically active surface area (ECSA) analysis results for the trimetallic Aurod-Pdshell-Ptcluster, bimetallic Aurod-Ptcluster and monometallic JM-Pt (used as a reference), which have respective ECSA values (cm(2)/mgPt) of 1883.0, 1371.7 and 879. The potential utility of the trimetallic catalysts was shown in a hydrogen peroxide sensing protocol, which showed the catalyst to have a sensitivity of 604 ìA/mMcm(2) within a linear range of 0.0013-6.191 mM.

Carbon materials with different morphology were prepared by reacting CCl 4 and Mo at 873–1173 K. At 873–973 K, hollow spheres (diameter: 1–3 μm, shell thickness: 50 nm) were obtained. At 1073 K, particles (diameter: 50–100 nm) encapsulated in spherical shells (diameter: 1–5 μm) were collected. At 1173 K, formation of particles (diameter: 200–300 nm) was observed. Mo acted as a reagent to remove chlorine atoms from the carbon source and a template for the formation of the spherical structures. We propose that reaction temperature and polymerization of chlorinated species formed from the pyrolysis of CCl 4 affect the morphology of carbon products greatly.

A simple galvanic reduction for direct growth of Au nanowires on silicon wafers is developed. The nanowires were prepared by reacting HAuCl4(aq) with Sn(s) in the presence of CTAC(aq) (cetyltrimethylammonium chloride) and NaNO3(aq), which were important to the product morphology development. The nanowire diameter was 50−100 nm, and the length was more than 20 µm.