Graphene Carbon Nanotubes Research Articles

Intrinsic Defect‐Rich Carbon‐Supported Iron Phthalocyanine as Beyond‐Pt Oxygen Reduction Catalysts for Zinc–Air Batteries

Molecular iron phthalocyanine (FePc) bearing a single‐atom Fe–N4 moiety is a high‐profile non‐platinum catalyst toward the oxygen reduction reaction (ORR), but its unsatisfactory activity and inadequate stability hinder the practical application. Herein, a novel strategy by hybridizing FePc with fullerene‐derived intrinsic defect‐rich carbon to improve its ORR activity and stability is reported. Via alkali‐assisted thermal pyrolysis, C60 molecules are disintegrated into tiny fragments that then restructure into pentagon‐ and edge‐rich carbon (FC). Utilizing FC as a support of FePc leads to a significantly improved ORR activity compared to other supports including reduced graphene oxide and carbon nanotube that hold distinct structural features. The optimized FePc/FC with a Fe loading of 3 wt% presents a half‐wave potential of 0.917 V, far beyond that of Pt/C (0.846 V), via selective four‐electron ORR pathway and excellent stability under accelerated stress test. The practical applicability of FePc/FC is also demonstrated as a high‐performing cathode catalyst of aqueous zinc–air batteries. It is, for the first time, explicitly disclosed that strong interactions between FePc molecules and intrinsic carbon defects (e.g., pentagons and edges) not only strengthen the anchoring effect of supported FePc but also enhance the intrinsic ORR activity of single‐atom Fe–N4 sites.

Synthesis Processes of Carbonaceous Material/Conducting Polymer Nanocomposites in Relation to Grafting and Electrochemical Properties for Supercapacitor Application: A Review

Supercapacitors are the energy storage devices that have gained increased attention due to high charge storage capacity, fast charge-discharge rate, high specific power and excellent cycle stability. Recently, research on supercapacitors is focused on the development of new electrode materials prepared by surface engineering to obtain superior electrochemical performance. Carbonaceous materials (CM) such as graphene, graphene oxide (GO), reduced graphene oxide (rGO) and carbon nanotubes (CNTs) etc. and conducting polymer (CP) based composite materials have gained increased attention for their use in supercapacitors. The nanocomposites obtained by merely mixing these two components pose some serious drawbacks such as low conductivity or poor film forming ability. The conjugation of CPs to CMs through covalent bonds is able to address these drawbacks. This review mainly provide collective information about various synthetic strategies to obtain CP grafted CMs for supercapacitor application. Herein, we provide information on different CP-CM conjugation reactions for obtaining the composites and their effects on electrochemical performances. The analysis revealed the importance of CP-CM grafting is important for tuning the electrochemical properties of the materials.

Performance analysis of carbon nanotube and graphene nanoribbon based biochemical sensors at atomic scale

Advancements in fabrication technologies have led to the possibility of synthesizing atomic-scale graphene nanoribbon (GNR) and carbon nanotube (CNT) based nanodevices. The purpose of this study was to model the electronic properties and electrical characteristics of these devices by atomistic modeling using density functional theory and the non-equilibrium Green’s function and compare the effects of molecular functionalization and sensing. The potential profile of the device was computed using the three-dimensional Poisson equation for smaller applied bias within one voltage range. Simulations showed a bandgap of 1 eV for armchair GNRs (AGNRs), which were insensitive to functionalized amine molecules, resulting in fewer alterations in the density of states (DoS), transmission spectra and the device current (ΔI). The bandgap further increased to 2 eV upon rolling the GNR into a armchair CNT (ACNT), which further decreased sensitivity. However, changing the configuration of the AGNR to a zigzag GNR (ZGNR) led to remarkable changes in the DoS and transmission spectra and a significant improvement in sensitivity. This improvement increased by 1.5–2 times upon rolling the ZGNR into a zigzag CNT (ZCNT). Thus, at lower dimensions in atomic scale, we found an alteration in device current of the carbon structures that was directly proportional to sensitivity in the following order: ΔI ACNT < ΔI AGNR < ΔI ZGNR < ΔI ZCNT. However, the same was found to fall for ZGNR and ZCNT with an increase in width to length (W/L) ratio. This highlights the importance of smaller atomic structures and this work provides a guideline for effective utilization of these structures for biochemical sensing.

Carbon-based self-powered terahertz detector with multi-walled carbon nanotubes-graphene heterostructure

A vertically aligned multi-walled carbon nanotubes (MWCNTs) array was synthesized via the chemical vapor deposition (CVD) method and subsequently transformed into horizontally ordered films using a mechanical roll-pressing technique, and these films were then stacked with graphene to form a van der Waals (vdW) heterostructure. In the metal-MWCNTs-graphene-metal structure, low-energy photon detection in the submillimeter-wave and terahertz (THz) spectral range is achieved at room temperature. The results demonstrate that without external bias conditions, the device exhibits a remarkable responsivity of up to 24.6 mA/W at 0.11 THz, with a response time of only 12.6 μs and a noise equivalent power as low as 64.1 pW Hz−0.5. These research findings represent an important step in exploring the efficient application of carbon-based materials in low-energy THz photon detection.

Investigation of thermoelectric properties of high concentration PEDOT: PSS inks doped with graphene and multi-walled carbon nanotubes

The use of wearable technologies in various aspects of life, particularly in health and entertainment, is experiencing a remarkable increase. This intensity of usage brings with it the energy needs of these devices. Polymer-based thermoelectric generator solutions are one of the most emphasized issues in energy harvesting applications and stand out as a solution method. In this study, we introduce a high-concentration poly(3,4-ethylenedioxy-thiophene): polystyrene sulfonate (PEDOT: PSS)-based conductive polymer ink, which has been doped with graphene and multi-walled carbon nanotubes (MWCNT) for thermoelectric applications. We also explore the film properties derived from this ink. The fabrication process involves cryogenic freezing, lyophilization, and re-dispersion of a mixture of water and dimethyl sulfoxide (DMSO) with a commercial PEDOT: PSS aqueous solution, followed by the addition of specific additives. These added compounds have led to a significant increase in electrical conductivity, resulting in materials with high electrical conductivity levels ranging from 100 to 200 S/cm. Remarkably, even after subjecting the material to 100 bending cycles, no significant change in electrical conductivity was observed. All the materials produced exhibited p-type semiconductor properties, and the high concentration of PEDOT: PSS, along with the addition of graphene and multi-walled carbon nanotubes, notably enhanced the Seebeck coefficient, reaching a maximum of 25 μV K⁻1.

Statistical analysis of coupled oscillations with a single fixed endpoint and its application to carbon nanomaterials

Squared deviations from the equilibrium positions of one-dimensional coupled harmonic oscillators with fixed and free endpoints are calculated, and the time averages are expressed as a function of the initial displacements and velocities. Furthermore, we consider the averages of squared deviations over an ensemble of initial displacements and velocities, which distribute based on a product of the same distribution functions with variances of the initial coordinates σx2 and velocities σv2 , respectively. We demonstrate that the mean squared deviation linearly increases as the oscillator separates further from the fixed endpoint because of the asymmetrical boundary conditions, and that the increase rate depends only on σv2 and not on σx2 . This simple statistical property of harmonic oscillation is similarly observed in the oscillations of a graphene sheet and carbon nanotube in molecular dynamics simulations, in which the interacting forces are nonlinear.

Electrospun polymeric nanohybrids with outstanding pollutants adsorption and electroactivity for water treatment and sensing devices

Graphene oxide (GO) and carbon nanotubes (CNTs) were loaded at different mutual ratios into poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) matrix and electrospun to construct mats that were assessed as smart sorbents for decontaminating water from methylene blue (MB) pollutant, while ensuring the additional possibility of detecting the dye amounts. The results revealed that sorption capacity enhances upon increasing GO content, which is beneficial to wettability and active area. Equilibrium adsorption of these materials is precisely predicted by the Langmuir isotherm model and the maximum capacities herein achieved, ranging from 120 to 555 mg/g depending on the formulation, are higher than those reported for similar systems. The evolution of the structure and properties of such materials as a function of dye adsorption was studied. The results reveal that MB molecules prompted the increase of electrical conductivity of the samples in a dose-dependent manner. Mats containing solely CNTs, while displaying the worst sorption performance, showed the highest electrical performances, displaying interesting changes in their electrical response as a function of the dye amount adsorbed, with a linear response and high sensitivity (309.4 µS cm−1 mg−1) in the range 0–235 µg of dye adsorbed. Beyond the possibility to monitor the presence of small amounts of MB in contaminated water and the saturation state of sorbents, this feature could even be exploited to transform waste sorbents into high-added value products, including flexible sensors for detecting low values of pressure, human motion, and so on.Graphical Multifunctional materials for dye absorption and detection, pressure sensing, fabricated by integrating GO and CNTs into PVDF-HFP matrix via electrospinning.

Welded Carbon Nanotube-Graphene Hybrids with Tunable Strain Sensing Behavior for Wide-Range Bio-Signal Monitoring.

Carbon nanotubes (CNTs) and graphene have commonly been applied as the sensitive layer of strain sensors. However, the buckling deformation of CNTs and the crack generation of graphene usually leads to an unsatisfactory strain sensing performance. In this work, we developed a universal strategy to prepare welded CNT-graphene hybrids with tunable compositions and a tunable bonding strength between components by the in situ reduction of CNT-graphene oxide (GO) hybrid by thermal annealing. The stiffness of the hybrid film could be tailored by both initial CNT/GO dosage and annealing temperature, through which its electromechanical behaviors could also be defined. The strain sensor based on the CNT-graphene hybrid could be applied to collect epidermal bio-signals by both capturing the faint skin deformation from wrist pulse and recording the large deformations from joint bending, which has great potential in health monitoring, motion sensing and human-machine interfacing.

Development of Composite Nanostructured Electrodes for Water Desalination via Membrane Capacitive Deionization.

Novel two-layer nanostructured electrodes are successfully prepared for their application in membrane capacitive deionization (MCDI) processes. Nanostructured carbonaceous materials such as graphene oxide (GO) and carbon nanotubes (CNTs), as well as activated carbon (AC) are dispersed in a solution of poly(vinyl alcohol) (PVA), mixed with polyacrylic acid (PAA) or polydimethyldiallylammonium chloride (PDMDAAC), and subsequently cast on the top surface of an AC-based modified graphite electrode to form a thin composite layer that is cross-linked with glutaraldehyde (GA). Cyclic voltammetry (CV) is performed to investigate the electrochemical properties of the composite electrodes and desalination experiments are conducted in batch mode using a MCDI unit cell to investigate the effects of i) the nanostructured carbonaceous material, ii) its concentration in the polymer blend, and iii) the molecular weight of the polymers on the desalination efficiency of the system. Comparative studies with commercial membranes are performed proving that the composite nanostructured electrodes are more efficient in salt removal. The improved performance of the composite electrodes is attributed to the ion exchange properties of the selected polymers and the increased specific capacitance of the nanostructured carbonaceous materials. This research paves the way for wider application of MCDI in water desalination.

Graphene Oxide, Carbon Nanotubes, and Polyelectrolytes-Based Impedanciometric E-Tongue for Estrogen Detection in Complex Matrices.

Currently, it is necessary to maintain the quality of aquifers and water bodies, which means the need for sensors that detect molecules as emerging pollutants (EPs) at low concentrations in aqueous complex solutions. In this work, an electronic tongue (e-tongue) prototype was developed to detect 17β-estradiol in tap water. To achieve such a prototype, an array of sensors was prepared. Each sensor consists of a solid support with interdigitated electrodes without or with thin films prepared with graphene oxide, nanotubes, and other polyelectrolytes molecules adsorbed on them. To collect data from each sensor, impedance spectroscopy was used to analyze the electrical characteristics of samples of estrogen solutions with different concentrations. To analyze the collected data from the sensors, principal components analysis (PCA) method was used to create a three-dimensional plane using the calculated principal components, namely PC1 and PC2, and the estrogen concentration values. Then, damped least squares (DLS) was used to find the optimal values for the hyperplane calibration, as the sensitivity of this e-tongue was not represented by a straight line but by a surface. For the collected data, from nanotubes and graphene oxide sensors, a calibration curve for concentration given by the 10PC1×0.492-PC2×0.14-14.5 surface was achieved. This e-tongue presented a detection limit of 10-16 M of 17β-estradiol in tap water.

Flexible Strain Sensors Based on Bionic Parallel Vein-like Structures for Human Motion Monitoring.

In recent years, strain sensors have penetrated various fields. The capability of sensors to convert physical signals into electrical signals is of great importance in healthcare. However, it is still challenging to obtain sensors with high sensitivity, large operating range and low cost. In this paper, a stretchable strain sensor made of a double-layer conductive network, including a biomimetic multilayer graphene-Ecoflex (MLG-Ecoflex) substrate and a multilayer graphene-carbon nanotube (MLG-CNT) composite up-layer was developed. The combined action of the two layers led to an excellent performance with an operating range of up to 580% as well as a high sensitivity (gauge factor (GFmax) of 1517.94). In addition, a pressure sensor was further designed using the bionic vein-like structure with a multi-layer stacking of MLG-Ecoflex/MLG-CNT/MLG-Ecoflex to obtain a relatively high deformation along the direction of thickness. The device presented a high sensing performance (up to a sensitivity of 0.344 kPa-1) capable of monitoring small movements of the human body such as vocalizations and gestures. The good performance of the sensors together with a simple fabrication procedure (flip-molding) make it of potential use for some applications, for example human health monitoring and other areas of human interaction.

Synthesis and applications of metal nanoparticles (Au, Ag)@C-graphene oxide and carbon nanotubes hybrid nanoarchitectures

In this work, we made an effort to use dopamine hydrochloride and the solid state method to anchor the gold and silver metallic nanoparticles over the graphene oxide-carbon nanotubes to improve the metal nanoparticles' interaction with the support materials. Because the hybrid nanoarchitectures of graphene-CNT provide enhanced electron transfer ability, which facilitates the catalytic activity more quickly and enhances the rate. Additionally, carbon nanotubes–graphene oxide-metal nanoparticles based hybrid catalyst was developed in a similar fashion. The formation of metallic nanoparticles in a size range of 3–15 nm is visible in the micrographs. These particles developed as nano-islands. The excess reductant formed as polydopamine acts as a stabilizer, and further, we utilise this polydoapmine into carbon by the calcination process. It results that carbonous materials will enhance the interaction between metal and support (CNT/GO). This leads to improved catalytic activity towards the reduction of 4-nitrophenol and catalytic decolorization of methylene blue at room temperature. The suggested technique for synthesizing metal nanoparticles over carbon nanostructures is simple and environmentally friendly.

Novel Surface-Enriched Spiky Ball With Spines NiCo2S4@GO/CNT Electrode Material for a High-Performance Flexible Asymmetric Supercapacitor

Nickel cobalt sulfide (NiCo2S4) nanoparticles on graphene oxide GO sheets and carbon nanotube (CNT) were fabricated successfully via a simple solvothermal route. Most NiCo2S4 nanoparticles cover both sides of the GO sheets, and the carbon nanotubes are arranged at the edge of the composite, creating a Spiky ball structure that effectively prevents the accumulation of GO. Synthesized hybrid nanocomposite (NiCo2S4/GO/CNT) has an optimum specific surface area and pore nature, and the coupling between CNT and GO enhances the electrochemical properties of NiCo2S4. The structural, morphological, and spectral characteristics were analysed using diffraction, microscopy, and spectroscopy techniques. To determine the electrochemical activity, cyclic voltammetry (CV), galvanostatic charge-discharge spectroscopy, and electrochemical impedance spectroscopy (EIS) were performed in a 3 M KOH electrolyte solution, the prepared sample was evaluated as an active electrode material for the supercapacitor. It delivers a very high specific capacitance of 845 Fg−1 at a current density of 2 Ag −1 as compared with NiCo2S4 (423 Fg−1). Coin cell was fabricated and tested using NiCo2S4/GO/CNT as cathode and graphite as an anode. The device exhibited an excellent energy density of 30.8 Wh kg−1, a power density of 3691 Wkg−1, and good cyclic stability with 82% retention after 1000 cycles.

Carbon nanotube graphene multilevel network based phase change fibers and their energy storage properties

Carbon nanotube graphene multilevel network based phase change fibers and their energy storage properties

Advanced hydrophobic cotton threads enhanced with graphene/SWCNT nanocomposites for exceptionally high electrical conductivity

This study investigates the fabrication and characterization of conductive threads using graphene and single-walled carbon nanotubes (SWCNTs), focusing on their application in wearable electronics and smart textiles. We employed the drop casting method to coat cotton threads with a polar solvent-based dispersion of graphene and SWCNTs, aiming to enhance their electrical conductivity and hydrophobic properties. Our results demonstrate that the electrical conductivity of these conductive threads significantly increases with the concentration of graphene and SWCNTs, reaching a peak conductivity of 68.75 S. cm−1 in threads coated with a SWCNT layer followed by a graphene layer. These threads exhibit metallic behavior across a broad temperature range (room temperature to 130 °C) and maintain electrical stability over an extended period. Additionally, varying degrees of hydrophobicity were observed among the different thread compositions. A washability study revealed that threads with a bilayer of SWCNT and graphene maintained higher electrical conductivity after multiple wash cycles compared to those fabricated with a mixed layer of these materials. This research not only highlights the potential of graphene and SWCNTs in developing advanced conductive threads but also addresses the challenges in scalability and reproducibility, paving the way for future innovations in smart textile applications.

Interface Welding via Thermal Pulse Sintering to Enable 4.6 V Solid‐State Batteries

AbstractNASICON‐type Li1.3Al0.3Ti1.7(PO4)3 (LATP) is one of the most promising solid‐state electrolytes (SSEs) to achieve high‐energy‐density solid‐state batteries (SSBs) due to its high ionic conductivity, high‐voltage stability, and low cost. However, its practical application is constrained by inadequate interfacial compatibility with cathode materials and significant incompatibility with lithium metal. In this work, a cost‐effective interface welding approach is reported, utilizing an innovative thermal pulse sintering (TPS) to fabricate LATP‐based solid‐state batteries. Initially, the rapid thermal pulses enhance the ionic conductivity of LATP SSE by inducing selective growth of LATP nanowires, effectively occupying interparticle voids. Additionally, this process results in the formation of a dense layer (GCM) comprising graphene oxide, carbon nanotubes, and MXene with a controlled Li+ transport pathway, facilitating lithium stripping and plating processes. Moreover, these thermal pulses facilitate the interfacial fusion between LATP and cathode materials, while avoiding undesired phase diffusion. As a result, SSBs with a LiCoO2 cathode deliver favorable cycle stability at 4.6 V, marking significant progress. This facile interface welding strategy represents a substantial step toward high‐energy‐density SSB development.

An advanced cement-based geocomposite with autonomous sensing and heating capabilities for enhanced intelligent transportation infrastructure

This study introduces an innovative multifunctional cementitious-based geocomposite with self-sensing and self-heating capability, generated for transportation infrastructural health monitoring and traffic recognition. In this route, hybrid graphene nanoplatelets (GNP) and carbon nanotubes (CNT) were uniformly dispersed within a matrix of stabilized sand containing 10% cement. The mechanical and microstructural performances of the composite were examined using various tests. The self-sensing capabilities of the composite were also investigated. In addition, the effects of temperature, moisture content, and loading shape, speed and magnitudes on the strain and stress sensing capability of the specimens were also investigated. The self-sensing performance of this cementitious geocomposite for the asphalt layer strain detection was assessed in a hybrid section including the asphalt mixture layer and smart geocomposite. Moreover, the research also examined the composite's capacity for self-heating, a highly relevant application within the transportation sector. The 0.98 ˚C/s heating rate, 526 mW/˚C heating power, and 251 ˚C maximum temperature proved the high heating potential of this geocomposite for deicing, self-healing, and temperature sensing applications. The specimens showed a supreme correlation between strain changes and fractional changes in electrical resistance (FCR) values in different loading patterns. Although increasing temperature amplified the piezoresistivity response of the composite, the introduction of humidity had adverse impacts. An appropriate correlation was observed between gauge factor, modulus, and digital image correlation analysis. The piezoresistive response of this geocomposite in the hybrid section including smart geocomposite and asphalt layer, representative of the common structural layers of urban pavements, showed the ability of this geocomposite in terms of strain and stress detection of itself and even in the asphalt layer. This study provides a bright horizon for smart materials development in civil infrastructures, particularly transportation and railways.

Cobalt Organic Framework Supported over Carbon-Based Materials as Novel Catalysts in the Hydrolysis of Sodium Borohydride

It is no secret that the global supplies of fossil fuel resources have been steadily dwindling. While there is no consensus on when the reserves will be completely depleted, there has been an effort among scientists to find a new, sustainable energy source for the future. It is generally agreed that such a source needs to not only be abundant, but also avoid the harmful biproducts of current fuel sources. Some proposed energy sources include solar, wind, geothermal and more. While each of these sources have their benefits, they also have their drawbacks and the cost to install and maintain these sources, as well as the environmental damage done during their construction can offset their benefits. One potential new energy source can be found in hydrogen gas. Hydrogen is not only the most abundant element in the universe, but its gaseous form can be burned to produce only energy and water [1-12]. The biggest hurdle a hydrogen economy faces is in the storage of the highly combustible gas. An interesting method of storing hydrogen is via adsorption within the chemical structure of a molecule. Sodium borohydride (NaBH4) for example is a chemical that contains 10.8% hydrogen by weight and steadily releases hydrogen gas when mixed with water.1 In order to efficiently utilize this reaction a catalyst is required. Typical catalysts are often precious metals like platinum, gold, and palladium, which tend to be expensive to use. By forming these metals into nanoparticles, their surface area can be increased, which increases their catalytic potential, however, these nanoparticles have a tendency to agglomerate in solution. Previous work by this team explored the catalytic capability of these metals and notes the use of carbon-based support structures can mitigate this agglomeration.2-4 This study aims to expand on those studies by using cobalt nanoparticles, which is a more cost-effective metal. Two novel Cobalt terephthalate complexes were combined with graphene and multiwalled carbon nanotubes (MWCNT) respectively, then tested for their ability to catalyze the hydrolysis of sodium borohydride. These materials were characterized using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Powdered X-ray diffraction (P-XRD), and Fourier Transform Infrared spectroscopy (FTIR). It was observed that after a single reaction, our materials appeared to be converted into cobalt borohydrides. The hydrogen produced for each material was 73 mL and 76 mL for the graphene and MWCNT materials, respectively. This study provides a possible method for producing cheaper, cleaner energy for a more sustainable future.

(Invited) New Synthesis Strategies to Develop High Performance Sulfur-Carbon Composites Cathodes for Lithium/Sulfur Batteries

Lithium/sulfur cells (Li/S) are recognized as a highly promising, inexpensive, and high-specific energy storage system due to the low cost of elemental sulfur and high theoretical specific capacity (1,675 mAh/g) of a sulfur cathode when paired with a lithium anode.1 However, practical applications of Li/S cells have been impeded by challenges related to sulfur cathodes, such as low sulfur conductivity of sulfur, the polysulfides shuttle, and changes in electrode microstructure during cycling.2-4 Sulfur-carbon (S-C) composites have been extensively studied as an effective approach to overcome these issues and improve the electrochemical performance of Li/S cells. Carbon materials, including graphene oxide, carbon nanotubes or nanofibers, and porous carbon, have been used in sulfur cathodes due to their high surface area, excellent electrical conductivity, and sulfur-immobilizing ability from their porous structure or surface functional groups.4 Designing high-performance S-C composites involves carefully considering various factors, such as the type of carbon materials, surface area or pore volume of carbon, sulfur-carbon weight ratio, and synthesis method, to achieve optimal performance. Key design strategies for high-performance S-C composites include: (1) confining nano-sized sulfur in porous carbon, (2) coating nano-sized sulfur onto sulfur-philic functional carbon surface, (3) engineering sulfur structures that form an adequate sulfur-electrolyte interface, and (4) preserving the electronically conductive carbon network in sulfur-carbon composite to minimize the electronic resistance of the sulfur cathode.4 S-C composites consisting of sulfur nanostructures confined in carbon porous structures or coated onto large sulfur-philic surface areas of carbon (e.g., graphene oxide) are promising composite designs as they can promote the kinetics and reversibility of the electrochemical process of the sulfur cathode. In this presentation, important recent findings about how to design and synthesize high performance S-C composite design will be introduced, and their effects on the electrochemical behavior of the sulfur cathode for Li/S cells will be discussed. References Bruce, P.G.; Freunberger, S.A.; Hardwick, L.J.; Tarascon, J.-M., Nat. Mater. 2012, 11, 19–29.Fotouhi, A.; Auger, D.J.; O’Neill, L.; Cleaver, T.; Walus, S., Energies 2017, 10, 1937.Peng, H.-J.; Huang, J.-Q.; Cheng, X.-B.; Zhang, Q., Adv. Energy Mater. 2017, 7, 1700260.Hwa, Y.; Cairn, E. J., ChemElectroChem 2020, 7, 3927-3942.

Supported Manganese Organic Framework as Catalyst for Hydrogen Evolution Reaction

The dependence on fossil fuels has caused significant harmful impact on the environment. The combustion of fossil fuels increases the harmful greenhouse gases including carbon dioxide and methane. The pollution not only worsens the impact of global warming but also affects human health. Many renewable energy sources have been discovered to replace fossil energy, but it is a challenge to find a cheap and effective energy source. Hydrogen arises as a potential candidate due to its high energy density and abundance. However, hydrogen was difficult to store. Hydrogen was often stored in liquid form at high pressure and extremely low temperature conditions. Another method of effectively storing hydrogen is by using hydrogen feedstock materials such as sodium borohydride. Sodium borohydride can be stored at room temperature and has a high gravimetric hydrogen capacity of 10% by weight. However, the process of extracting hydrogen from the materials was slow so it required catalysts. Many precious metal catalysts such as gold and silver catalyst have been applied to improve hydrogen generation reaction, but those metal catalysts were expensive to create. Additionally, those metal catalysts were often agglomerate and impossible to reuse. In this study, we used a non-precious metal complex supported over carbon-based materials to catalyze the hydrogen evolution reaction. We discovered a novel method of synthesizing manganese terephthalate complex at room temperature. The metals complex was coupled with graphene (G) and multiwalled carbon nanotubes (MWCNT) to increase its durability and efficiency. Each material was characterized by Powdered X-ray diffraction (P-XRD), Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). During the reaction with sodium borohydride, we discovered that the manganese terephthalate complex converted to manganese boride and further improved the catalysis process. In the first trial, the reaction catalyzed by Mn complex coupled with MWCNT produced 25ml of hydrogen. At the fifth reuse trials, the amount of generated hydrogen (~44 ml) was nearly doubled. A similar phenomenon was observed in Mn complex coupled with graphene. This study introduces a novel method in synthesizing a stable, cheap and efficient catalyst for hydrogen evolution.