Graphite Surface Research Articles

Recycled graphite enabled superior performance for lithium ion batteries

Recycling graphite attracts growing attention since cumulative amount of spent Li-ion batteries and the shortage of graphite supply chain. Although various recycling methods have been reported, the recycled graphite cannot reach the strict commercial standards of purity, scalability, efficiency, and capacity, preventing it from battery manufacturing. Herein, the important roles of defects and functional groups on the graphite surface are deeply studied, and a closed-loop graphite recycling process with the surface recovery and modification for the graphite from the end-of-life batteries is demonstrated. The recovered graphite delivers a purity of over 99.9 % and an average initial coulombic efficiency of 91.5 %. Compared with commercial graphite in industrial standard battery testing parameters, full cells with recovered graphite possess enhanced rate reversibility, doubled cycle life, over 10 % higher capacity along with half anode material cost. These impressive results not only underscore the transformative potential of surface reconstruction and modification in graphite recycling, but also present economic feasibility and sustainable pathway for significantly improving battery performance and addressing global resource challenges via integration with the hydrometallurgical recycling process.

Rheological properties and excellent thermal shock stability of Al2O3-SiC-C castables containing continuous TiC coated graphite

High-flux molten iron and intermittent circulation accelerated the damage process of Al2O3-SiC-C castables under alternating thermal stress. A continuous TiC coated graphite was prepared using sol-gel combined with carbothermal reduction to investigate its influence on the flow properties, microstructure, mechanical properties and thermal shock resistance of Al2O3-SiC-C castables. The results show that a lower Ti/C molar ratio and higher heat treatment temperature are more favorable for the synthesis of TiC and the formation of a continuous and complete TiC coated graphite layer on the graphite surface. The introduction of TiC coated graphite significantly enhance the mechanical properties and thermal shock stability of Al2O3-SiC-C castables, with a remarkable 227% increase in residual strength after thermal shock. In addition, during the oxidation process of the samples with TiC coated graphite, TiO2 generated from the oxidation of TiC fills the pores and facilitates the growth of Al6Si2O13, which enhances the tightness of the bonding of the castable matrix, thus contributing to the improvement of the overall performance.

Coupling effect of gas solubility in a solvent and substrate structure on performance in nanobubble morphological changes

The distribution morphologies of nanobubbles on Highly Oriented Pyrolytic Graphite (HOPG) surfaces prepared using the alcohol-water exchange test method were observed using atomic force microscopy. In situ observation revealed the distinct growth evolution behavior of nanobubble morphology. Molecular dynamics simulation was employed to replicate the experimental test and investigate the influence of the coupling effect of gas solubility and substrate structure on the morphological features of nanobubble distribution in alcohol-water exchange experiments. The results demonstrate that gas solubility plays a pivotal role in the nucleation of surface nanobubbles during alcohol-water exchange. Specifically, stable surface nanobubbles form only when the solubility exceeds 0.02535. Furthermore, under conditions where gas solubility satisfies the nucleation criteria, the surface potential energy of concave and defective structures exhibits concave characteristics, giving rise to the nucleation of cap-shaped nanobubbles. In contrast, the step structure, characterized by the smallest average surface potential energy, results in relatively flat properties in the lowest area, with nanobubble nucleation taking the form of layer-shaped features. yields relatively uniform characteristics at the lowest level, where nanobubble nucleation manifests in the form of layered features. As time progresses, cap-shaped nanobubbles coalesce, leading to the escape of gas molecules and subsequent dissipation, whereas the layer-shaped nanobubbles adsorb gas molecules from the solution, prompting their expansion.

One-step ultrafast laser-induced graphitization on PS-SiC surfaces for superior friction performance

Pressureless sintered silicon carbide (PS-SiC) ceramics are widely used as friction materials in the aerospace industry, and enhancing the self-lubricating properties of PS-SiC ceramics under dry friction is highly significant. In this study, an infrared femtosecond laser was used to treat the surface of PS-SiC ceramics, and the effects of various processing parameters on surface microstructure, chemical composition, and graphitization degree were investigated. More importantly, SiC decomposes into amorphous carbon and stays on the surface of PS-SiC ceramics under the photothermal effect, and the amorphous carbon realizes the transition to the ordered graphite structure by controlling the laser energy. The highly graphitized, carbon-containing micro/nanostructures on the surface of laser-treated PS-SiC ceramics promote the formation of stable carbon-based tribofilms during sliding, which significantly enhances the tribological properties of PS-SiC ceramics under dry friction. This study proposes a method for inducing graphitization on the surface of PS-SiC ceramics using an infrared femtosecond laser, providing a manufacturing approach and theoretical support for the development of high-performance PS-SiC ceramic friction materials.

Incorporation of phenylcarbonyl groups in the sidechain: A tool to induce ordered assembly of peptides on surfaces.

The possibility of introducing various functionalities on peptides with relative ease allows them to be used for molecular applications. However, oligopeptides prepared entirely from proteinogenic amino acids seldom assemble as ordered structures on surfaces. Therefore, sidechain modifications of peptides that can increase the intermolecular interactions without altering the constitution of a given peptide become an attractive route to self-assembling them on surfaces. We find that replacing phenylalanine residues with unusual amino acids that have phenylcarbonyl sidechains in oligopeptides increases the formation of ordered self-assembly on a highly ordered pyrolytic graphite surface. Peptides containing the modified amino acids provided extended long-range ordered assemblies, while the analogous peptides containing phenylalanine residues failed to form long-range assemblies. X-ray crystallographic analysis of the bulk structures of these peptides and the analogous peptides containing phenylalanine residues reveal that such modifications do not alter the secondary structure in crystals. It also reveals that the secondary hydrogen bonding interaction through phenylcarbonyl sidechains facilitates extended growth of the peptides on graphite.

Achieving precise graphenization of diamond coatings below the interfacial thermal stress threshold

Abstract Diamond coatings possess numerous excellent properties, making them desirable materials for high-performance surface applications. However, without a revolutionary surface modification method, the surface roughness and friction behavior of diamond coatings can impede their ability to meet the demanding requirements of advanced engineering surfaces. This study proposed the thermal stress control at coating interfaces and demonstrated a novel process of precise graphenization on conventional diamond coatings surface through laser induction and mechanical cleavage, without causing damage to the metal substrate. Through experiments and simulations, the influence mechanism of surface graphitization and interfacial thermal stress was elucidated, ultimately enabling rapid conversion of the diamond coating surface to graphene while controlling the coating's thickness and roughness. Compared to the original diamond coatings, the obtained surfaces exhibited a 63–72% reduction in friction coefficients, all of which were below 0.1, with a minimum of 0.06, and a 59–67% decrease in specific wear rates. Moreover, adhesive wear in the friction counterpart was significantly inhibited, resulting in a reduction in wear by 49–83%. This demonstrated a significant improvement in lubrication and inhibition of mechanochemical wear properties. This study provides an effective and cost-efficient avenue to overcome the application bottleneck of engineered diamond surfaces, with the potential to significantly enhance the performance and expand the application range of diamond-coated components.

Preparation and Formation Mechanism of β-SiC Coatings Using a SiCl4-CH4-H2-N2 System.

The mechanism of β-SiC preparation via chemical vapor deposition (CVD) of the SiCl4-CH4-H2-N2 system remains unclear. Consequently, the change of molar Gibbs free energy of the CVD β-SiC chemical reaction in the SiCl4-CH4-H2-N2 system has been studied by the Helsinki Software Corporation (HSC) Chemistry code for the first time. The role of nitrogen in the reaction was confirmed. Seven potential reaction pathways of CVD β-SiC were presented, and the thermodynamic equilibrium components of each reaction were calculated systematically. The most viable reaction pathway and corresponding optimal temperature range for CVD β-SiC were determined. In addition, a kinetic study of CVD β-SiC was conducted. The microscopic morphology and crystal structure of β-SiC coatings prepared on the graphite surface at different temperatures were charactered by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman, etc. Ultimately, through SEM, XRD, and Raman observation, uniform and dense β-SiC coatings with fine grains and high crystallinity were successfully obtained. Furthermore, large β-SiC-coated graphite trays with diameters of 230 and 465 mm were prepared by CVD using the SiCl4-CH4-H2-N2 system, and the average thickness of β-SiC was about 100.6 μm. This study provides a theoretical basis and technical recommendations for the fabrication of SiC-coated graphite trays used in metal-organic chemical vapor deposition (MOCVD) equipment.

Enhancing Performance of Composite-Based Triboelectric Nanogenerators Through Laser Surface Patterning and Graphite Coating for Sustainable Energy Solutions

The performance of composite-based triboelectric nanogenerators (C–TENGs) was significantly enhanced through laser surface patterning and graphite coating. The laser etching process produced accurate and consistent patterns, increasing surface area and improving charge accumulation. SEM imagery confirmed the structural differences and enhanced surface properties of the laser-etched C–TENGs. Graphite fibers further augmented the contact surface area, enhancing charge accumulation and diffusion. Experimental results demonstrated that the optimized C–TENGs, especially those with line patterns and graphite coating, achieved a maximal 98.87 V open-circuit voltage (VOC) and a 0.10 µA/cm2 short-circuit current density (JSC) under a 20 N external force. Environmental tests revealed a slight decrease in performance with increased humidity, while long-term stability tests indicated consistent performance over three weeks. Practical application tests showed the potential of C–TENGs integrated into wearable devices, generating sufficient energy for low-power applications, thereby highlighting the promise of these devices for sustainable energy solutions.

Helmholtz Plane Regulation Empowers PF6− Permselectivity Towards High Coulombic Efficiency Dual Ion Battery of 5.5 V

AbstractHigh‐voltage dual ion battery (DIB) is promising for stationary energy storage applications owing to its cost‐effectiveness, which has been a hot topic of research in rechargeable battery fields. However, it still suffers from rapid battery failure caused by the severe solvent co‐intercalation and electrolyte oxidation. To address these bottlenecks, herein a functional electrolyte additive hexafluoroglutaric anhydride (HFGA) is presented based on a Helmholtz plane regulation strategy. It is demonstrated that the HFGA can precisely enter into the Helmholtz plane and positively regulate anion solvation behaviors near the graphite electrode surface owing to its considerable H−F affinity with ethyl methyl carbonate (EMC), thus alleviating EMC‐related co‐intercalation and oxidation decomposition during DIB charging. Meanwhile, HFGA can copolymerize with the presence of PF5 at the Helmholtz plane to participate in forming a CF2‐rich CEI layer with excellent PF6− permselectivity, conducive to achieving PF6− de‐solvation and simultaneously suppressing electrolyte oxidation decomposition. By virtue of such beneficial effects, the graphite cathode enables a 5.5 V DIB with a prominent capacity retention of 92 % and a high average Coulombic efficiency exceeding 99 % within 2000 cycles at 5 C, demonstrating significantly enhanced electrochemical reversibility. The Helmholtz plane regulation strategy marks a milestone in advancing DIB technologies.

Helmholtz Plane Regulation Empowers PF6 - Permselectivity Towards High Coulombic Efficiency Dual Ion Battery of 5.5 V.

High-voltage dual ion battery (DIB) is promising for stationary energy storage applications owing to its cost-effectiveness, which has been a hot topic of research in rechargeable battery fields. However, it still suffers from rapid battery failure caused by the severe solvent co-intercalation and electrolyte oxidation. To address these bottlenecks, herein a functional electrolyte additive hexafluoroglutaric anhydride (HFGA) is presented based on a Helmholtz plane regulation strategy. It is demonstrated that the HFGA can precisely enter into the Helmholtz plane and positively regulate anion solvation behaviors near the graphite electrode surface owing to its considerable H-F affinity with ethyl methyl carbonate (EMC), thus alleviating EMC-related co-intercalation and oxidation decomposition during DIB charging. Meanwhile, HFGA can copolymerize with the presence of PF5 at the Helmholtz plane to participate in forming a CF2-rich CEI layer with excellent PF6 - permselectivity, conducive to achieving PF6 - de-solvation and simultaneously suppressing electrolyte oxidation decomposition. By virtue of such beneficial effects, the graphite cathode enables a 5.5 V DIB with a prominent capacity retention of 92 % and a high average Coulombic efficiency exceeding 99 % within 2000 cycles at 5 C, demonstrating significantly enhanced electrochemical reversibility. The Helmholtz plane regulation strategy marks a milestone in advancing DIB technologies.

Manganese-modified biochar for sediment remediation: Effect, microbial community response, and mechanism

Heavy metal sediment pollution has become an increasingly serious problem associated with industrial development, so extensive studies have been conducted concerning their removal. Biochar has recently shown good potential for in-situ remediation of heavy metal-contaminated sediments. The heavy metal adsorption capacity of inexpensive biochar can be improved by loading it with metal oxides. In this study, manganese-modified biochar (MBC) was prepared by KMnO4-modified waste-activated sludge biochar and applied to immobilize Pb and Cd in sediments. Its effects on the sediment microbial community were also investigated. The Results showed that manganese modification of the biochar made it more conducive to the adsorption of heavy metals, owing to its higher specific surface area and graphitization structure, more active sites and oxygen-containing groups, and the presence of Mn2O3 crystal structure on the surface. The maximum adsorption capacities of this material for Pb2+ and Cd2+ in solution were 176.9 mg/g and 44.0 mg/g, respectively. The application of MBC to the remediation of heavy metal-contaminated sediments transformed Pb and Cd in the sediments from exchangeable to residual state. The F4 content of Pb in the sediments increased from 40.52%-42.36% to 49.11%–51.14% after application of 1% MBC, and to 63.94%–64.49% after application of 5% MBC. Correspondingly, the F1 content of Pb in the sediments decreased from 29.09%-30.68% to 17.43%–17.69% after the application of 5% MBC. Furthermore, MBC efficiently enriched the microbial biodiversity and affected the microbial population structure within 60 days. The relative abundance of uncultured f Symbiobacteraceae and Fonticella communities significantly increased after incubation. The results may provide empirical support for the combination of metal oxides and biochar for the remediation of heavy metal-contaminated sediments.

Outstanding Activity and Durability of Supported NiCo2O4 Nanoparticles for Direct Ethanol Fuel Cells

ABSTRACTThe rational design of noble metal‐free electrocatalysts represents one of the basic stones for fuel cell development. With the exploration of eco‐friendly nanomaterials for the investigated alcohol oxidation process, nickel‐based electrodes have been recognized as the most auspicious anodes with promoted activity and stability. In this work, a series of NiCo2O4 nanoparticles were deposited onto graphite sheets (NiCo2O4/T) introducing varied proportions of cobalt oxide species. Co‐precipitation protocol of the respective metallic hydroxides onto the carbonaceous support was followed with consecutive annealing in an air atmosphere at 400°C. The fabricated mixed metallic oxide nanopowder was physically studied using X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X‐ray analysis (EDX), X‐ray photoelectron spectroscopy (XPS), and selected area electron diffraction (SAED). Uniformly arranged nanoparticles were observed on graphite surface as evidenced by SEM and TEM. The cubic lattice structure of formed NiCo2O4 crystals was also confirmed by XRD through the defined peaks of binary metallic oxides clarifying their successful preparation scheme. The electrocatalytic properties of these NiCo2O4/T nanocatalysts were evaluated for oxidizing ethanol molecules in basic solution. Pronounced oxidation current densities were remarkably measured at NiCo2O4/T electrodes in relation to that at NiO/T. Differing the introduced cobalt oxide content into the synthesized nanocatalyst significantly controlled its catalytic performance. NiCo2O4/T‐20 exhibited the highest activity and stability among the prepared nanomaterials. Much decreased charge transfer resistances were also recorded at this electrode demonstrating its promoted electron transfer characteristics. This work could provide a reasonable route for the simple synthesis of comparable transition metallic oxides with promising attitudes for energy generation purposes.

Nanoscale friction and wear of graphite surface in ambient and underwater conditions

The tribological properties of graphite are extremely sensitive to surrounding environment, which affects its longevity and friction reduction performance. This study aims to develop a comprehensive understanding of the effects of a liquid environment on interactions at the sliding interface, thereby influencing the nanoscale tribological properties of graphite surfaces. By combining atomic force microscopy experiments and molecular dynamics simulations, we conducted a comparative analysis of friction and wear behavior of graphite under two different environmental conditions: ambient (air) and underwater condition. Our investigations explored both the step edge and interior (step-free) graphite surfaces. The experimental results revealed a notable contrast in the frictional and wear behavior of graphite at nanoscale in these two environments. The interior surface exhibited a friction coefficient (COF) of approximately 0.003 and 0.006 against a diamond-coated surface in ambient and underwater conditions, respectively. Interestingly, the underwater environment not only increased friction but also significantly compromised the wear resistance of graphene layers near the graphite surface compared to the ambient environment, as evidenced in both step edge and interior step-free regions. The interior region sustained up to ∼7400 nN load in ambient condition but failed at ∼1500 nN under water. Similarly, the step edge failed at ∼375 and ∼187.5 nN in ambient and underwater conditions, respectively. Our simulations revealed that the increased friction in underwater condition is due to resistance of surrounding water molecules during tip sliding. The presence of water at tip-graphite contact interface generated substantial localized stress, leading to the initiation of wear and revealing the pronounced effect of water on the wear characteristics of graphite in underwater condition.

Metal single-atom interaction with graphitic C3N4 surface based on density functional theory calculations and linear regression analysis

This paper discusses the adsorption of metal single-atoms (SAs) on graphitic C3N4 (gCN) multilayered surface models based on density functional theory (DFT) calculations. We systematically searched stable adsorption sites on gCN and showed that the cavity site is preferred for metal SAs. We also discussed the usefulness of several descriptors, such as the distance between the SA and gCN, charge donation (electron transfer), and atomic radius, for evaluating the SA adsorption energy, based on the linear regression method. In addition, the most stable adsorption energy for fifth- and sixth-row metals can be predicted using only the “group” descriptor of the periodic table. The group descriptor is closely related to the atomic radius, and hence the stability of fifth- and sixth-row metals is determined from the fit between the SA radius and the gCN cavity size. The study findings facilitate the development of various metal-dopant techniques for gCN-based applications.

Binary imidazolium based aqueous ionic liquid droplet on a rough surface: a molecular dynamics study

Ionic liquids (ILs) have garnered immense attention due to their tunable physicochemical properties. In this study, we delve into the wetting behaviour and interfacial properties of aqueous binary IL mixtures containing [EMIM] [BF4] and [HMIM] [BF4] on both smooth and rough graphite surfaces. Employing classical molecular dynamics simulations, we systematically explored the effects of IL concentration and surface morphology on wetting phenomena. To ensure the equilibrium of the systems, we began by calculating the interaction energies between the components. Subsequently, contact angles were computed, shedding light on the wetting characteristics of the aqueous binary IL mixtures. We meticulously examined the density profiles of the IL systems from the substrate to unravel the dominance of one IL over the other, exploiting the hydrophilic nature of [EMIM] [BF4] and the hydrophobic nature of [HMIM] [BF4]. A comprehensive analysis of hydrogen bond distribution allowed us to discern the intricate nature of these aqueous binary IL droplets. We probed the changes in intermolecular forces within the aqueous IL solution by investigating surface tensions. The tunability of these ILs emerges as a significant aspect of our study, paving the way for their tailored application in engineering and scientific domains. Schematic diagram showing the density distribution of hydrophilic and hydrophobic ILs ([EMIM] [BF4] and [HMIM] [BF4]) in water and also the hydrogen bond (HB) distribution of anion ([BF4]−) water inside the droplet on a pillared surface with a surface fraction ( f ) of 0.4 and pillar height of H = 4 .

Supramolecular Anchoring of Fe(III) Molecular Redox Catalysts into Graphitic Surfaces Via CH‐π and π–π Interactions for CO2 Electroreduction

AbstractPhotoelectrochemical devices require solid anodes and cathodes for the easy assembling of the whole cell and thus redox catalysts need to be deposited on the electrodes. Typical catalyst deposition involves drop casting, spin coating, doctor blading or related techniques to generate modified electrodes where the active catalyst in contact with the electrolyte is only a very small fraction of the deposited mass. We have developed a methodology where the redox catalyst is deposited at the electrode based on supramolecular interactions, namely CH‐π and π–π between the catalyst and the surface. This generates a very well‐defined catalysts‐surface structure and electroactivity, together with a very large catalytic response. This approach represents a new anchoring strategy that can be applied to catalytic redox reactions in heterogeneous phase and compared to traditional methods involves about 4–5 orders of magnitude less mass deposition to achieve comparable activity and with very well‐behaved electroactivity and stability.

Molecular recognition characteristics of co-assembled peptides on atomically flat graphite surfaces

Molecular recognition, involving the binding of two or more molecules, is widely found in multiple disciplines. It plays a crucial role in driving specific molecular functionalization or biological activities such as antigen–antibody interactions. Recently, the molecular recognition of single peptides self-assembly at interfaces has been widely investigated since their broad applications in biosensors and bioelectronics. However, the recognition characteristics of peptide-peptide co-assembly on solids has not been investigated yet, which provides a basis for potential multi-probes biosensing or structure-intermingled functionalized bioelectronic applications. Here, we explored the molecular recognition characteristics of co-assembled peptides on two-dimensional (2D) layered nanomaterials, specifically graphite. Our findings showed distinct surface characteristics of peptide co-assembly in comparison to the independent peptides self-assembly. Peptide co-assembly exhibited the nucleation and growth heterogeneities with reduced nucleation and growth rates, dominated by a diffusion-limited step as confirmed via carrying out the sequential-assembled experiments. Moreover, molecular dynamics simulation reveals a slowdown binding process of co-assembled peptides to graphite. Furthermore, the misattachment of one peptide to arrays of another types of peptide with distinct structural ordering orientations severely postponed peptide elongation. Therefore, our work provides valuable insight into the fundamental surface characteristics of two co-assembled peptides as they specifically recognize graphite surface via undergoing continuous surface behaviors from binding to diffusion until final ordering process. The formation of co-assembled peptide patterns on 2D layered nanomaterials incorporates multiple functions enabling to provide potential applications in intermingled peptide-based biosensing or bioelectronic nanodevices.

Characterizing the surface compositions of supported bimetallic PtSn clusters: Effects of cluster-support interactions and surface adsorbates

PtSn bimetallic clusters on TiO2(110) and highly oriented pyrolytic graphite (HOPG) surfaces have been characterized by scanning tunneling microscopy, low energy ion scattering (LEIS), X-ray photoelectron spectroscopy, and temperature programmed desorption (TPD); density functional theory (DFT) calculations have also been performed to better understand adsorption of CO and D2 on the PtSn surfaces. On TiO2 at coverages of 2 ML of Pt and 2 ML of Sn, exclusively bimetallic clusters are formed for both orders of deposition because clusters of the first metal completely cover the surface such that all atoms of the second metal are incorporated into the existing clusters. In contrast, on HOPG, the high mobility and weak cluster-support interactions on HOPG result in much larger 2 ML monometallic clusters (∼30 Å high) that do not completely cover the surface, and deposition of the second metal produces larger clusters as well as smaller ones. Despite the difference in cluster morphologies for the different orders of deposition and supports, the LEIS experiments demonstrate that in all cases, the PtSn clusters are rich in Sn at the surface, as expected based on the lower surface free energy for Sn compared to Pt. Furthermore, the +0.2 eV shift in the Sn(3d5/2) binding energy observed on all surfaces in the presence of Pt is consistent with PtSn alloy formation. Deposition of 2 ML of Sn on TiO2 produces two-dimensional clusters with oxidation of Sn and reduction of titania at the cluster-support interface, but addition of Pt to the Sn clusters causes Sn to diffuse away from this interface, leaving Sn in the metallic state. TPD experiments on 2 ML Pt/TiO2 with increasing coverages of Sn show that the number of adsorption sites for D2 sharply decreases to nearly zero at 0.5 ML, while CO adsorption decreases to zero only at much higher Sn coverages of 2 ML. DFT studies for Sn modified Pt surfaces and bulk structures demonstrate that for CO adsorption at low Sn coverages (≤0.25 ML), the strong Pt-CO interactions induce diffusion of Pt to the cluster surface and the formation of a bulk Pt3Sn alloy, whereas D2 adsorption does not lead to interactions with the Pt surface that are strong enough to induce alloy formation. A single Sn adatom prevents D2 adsorption on four neighboring Pt atoms via site-blocking and the donation of electron density to Pt.

Co-complexes on modified graphite surface for steady green hydrogen production from water at neutral pH.

Green hydrogen production from water is one attractive route to non-fossil fuel and a potential source of clean energy. Hydrogen is not only a zero-carbon energy source but can also be utilized as an efficient storage of electrical energy generated through various other sources, such as wind and solar. Cost-effective and environmentally benign direct hydrogen production through neutral water (∼pH 7) reduction is particularly challenging due to the low concentration of protons. There is currently a major need for easy-to-prepare, robust, as well as active electrode materials. Herein we report three new molecular electrodes that were prepared by anchoring commercially available, and environmentally benign cobalt-containing electrocatalysts with three different ligand frameworks (porphyrin, phthalocyanine, and corrin) on a structurally modified graphite foil surface. Under the studied reaction conditions (over 7h at 22°C), the electrode with Co-porphyrin is the most efficient for the water reduction with starting ∼740mV onset potential (OP) (vs. RHE, current density 2.5mA/cm2) and a Tafel slope (TS) of 103mV/dec. It is followed by the molecular electrodes having Co-phthalocyanine [825mV (OP), 138mV/dec (TS)] and Vitamin-B12 (Co-corrin moiety) [830mV (OP), 194 mv/dec (TS)]. A clear time-dependent improvement (>200mV over 3h) in the H2 production overpotential with the Co-porphyrin-containing cathode was observed. This is attributed to the activation due to water coordination to the Co-center. A long-term chronopotentiometric stability test shows a steady production of hydrogen from all three cathode surfaces throughout seven hours, confirmed using an H2 needle sensor. At a current density of 10mA/cm2, the Co-porphyrin-containing electrode showed a TOF value of 0.45s-1 at 870mV vs. RHE, whereas the Co-phthalocyanine and Vitamin-B12-containing electrodes showed 0.37 and 0.4s-1 at 1.22V and 1.15V (vs. RHE), respectively.

Piezo tube stacked scanning tunneling microscope for use in extreme and confined environments

Scanning Tunneling Microscopy (STM) is widely used for observing atomic structures due to its ultra-high spatial resolution. As the core units of STM, the coarse stepper motor and imaging unit, have conflicting size requirements for piezo tubes. Longer piezo tubes yield greater output force and easier movement for the motor, while shorter tubes enhance imaging precision and stability for the scanner. Traditional STMs typically employ a large piezo tube for coarse stepping and a smaller one for independent imaging to address this issue. Here, we present the new design of a piezo tube stacked STM, in which two independent piezo tubes act together during tip-sample approach process and only one shorter tube works during scanning imaging. Both tubes are fixed to the framework, ensuring high rigidity and compactness. The new design enables us to achieve both coarse stepping and imaging functions with a total length of only 25 mm for the two tubes, effectively reducing the length of whole STM, facilitating its integration into narrow low-temperature spaces for imaging applications. Using this device, we obtained high-quality atomic images of graphite sample surfaces at room temperature. Continuous scanning imaging of the same area on Au film at 300 K demonstrates the STM’s high stability in both X-Y and Z directions. Atomic images, I-V spectra, and di/dv spectra obtained at 2 K on graphite surface illustrate the excellent application potential of this device in low-temperature environments. Finally, atomic images obtained of graphite in sweeping the magnetic fields from 0 T to 11 T in a huge vibrational dry magnet prove the new STM’s excellent performance in extreme conditions.