Free-standing electrochemically coated MoSx based 3D-printed nanocarbon electrode for solid-state supercapacitor application

Aqueous Multivalent Metal-ion Batteries: Toward 3D-printed Architectures

Energy storage has become increasingly crucial, necessitating alternatives to lithium-ion batteries due to critical supply constraints. Aqueous multivalent metal-ion batteries (AMVIBs) offer significant potential for large-scale energy storage, leveraging the high abundance and environmentally benign nature of elements like zinc, magnesium, calcium, and aluminum in the Earth's crust. However, the slow ion diffusion kinetics and stability issues of cathode materials pose significant technical challenges, raising concerns about the future viability of AMVIB technologies. Recent research has focused on nanoengineering cathodes to address these issues, but practical implementation is limited by low mass-loading. Therefore, developing effective engineering strategies for cathode materials is essential. This review introduces the 3D printing-enabled structural design of cathodes as a transformative strategy for advancing AMVIBs. It begins by summarizing recent developments and common challenges in cathode materials for AMVIBs and then illustrates various 3D-printed cathode structural designs aimed at overcoming the limitations of conventional cathode materials, highlighting pioneering work in this field. Finally, the review discusses the necessary technological advancements in 3D printing processes to further develop advanced 3D-printed AMVIBs. The reader will receive new fresh perspective on multivalent metal-ion batteries and the potential of additive technologies in this field.

Electrochemical Deposition and Etching of Quasi-Two-Dimensional Periodic Membrane Structure

In this paper, two experimental procedures are reported, namely electro-deposition in the ultrathin liquid layer and chemical micro-etching. Firstly, a large area quasi-two-dimensional periodic membrane with adjustable density is deposited on a Si substrate driven by half-sinusoidal voltage, which is composed of raised ridges and a membrane between the ridges. The smaller the voltage frequency is, the larger the ridge distance is. The height of a raised ridge changes synchronously with the amplitude. The grain density distribution of membrane and raised ridge is uneven; the two structures change alternately, which is closely related to the change of growth voltage and copper ion concentration during deposition. The structural characteristics of membrane provide favorable conditions for micro-etching; stable etching speed and microscope real-time monitoring are the keys to achieve accurate etching. In the chemical micro-etching process, the membrane between ridges is removed, retaining the raised ridges, thus a large scale ordered micro-nano wires array with lateral growth was obtained. This method is simple and controllable, can be applied to a variety of substrates, and is the best choice for designing and preparing new functional materials. This experiment provides a basis for the extension of this method.

Multi-walled carbon nanotubes/carbon black/rPLA for high-performance conductive additive manufacturing filament and the simultaneous detection of acetaminophen and phenylephrine

The combination of multi-walled carbon nanotubes (MWCNT) and carbon black (CB) is presented to produce a high-performance electrically conductive recycled additive manufacturing filament. The filament and subsequent additively manufactured electrodes were characterised by TGA, XPS, Raman, and SEM and showed excellent low-temperature flexibility. The MWCNT/CB filament exhibited an improved electrochemical performance compared to an identical in-house produced bespoke filament using only CB. A heterogeneous electrochemical rate constant, [Formula: see text] of 1.71 (± 0.19) × 10-3 cm s-1 was obtained, showing an almost six times improvement over the commonly used commercial conductive CB/PLA. The filament was successfully tested for the simultaneous determination of acetaminophen and phenylephrine, producing linear ranges of 5-60 and 5-200 μM, sensitivities of 0.05 μA μM-1 and 0.14 μA μM-1, and limits of detection of 0.04 μM and 0.38 μM, respectively. A print-at-home device is presented where a removable lid comprised of rPLA can be placed onto a drinking vessel and the working, counter, and reference components made from our bespoke MWCNT/CB filament. The print-at-home device was successfully used to determine both compounds within real pharmaceutical products, with recoveries between 87 and 120% over a range of three real samples. This work paves the way for fabricating new highly conductive filaments using a combination of carbon materials with different morphologies and physicochemical properties and their application to produce additively manufactured electrodes with greatly improved electrochemical performance.

Current Trends and Promising Electrode Materials in Micro-Supercapacitor Printing

The development of scientific and technological foundations for the creation of high-performance energy storage devices is becoming increasingly important due to the rapid development of microelectronics, including flexible and wearable microelectronics. Supercapacitors are indispensable devices for the power supply of systems requiring high power, high charging-discharging rates, cyclic stability, and long service life and a wide range of operating temperatures (from -40 to 70 °C). The use of printing technologies gives an opportunity to move the production of such devices to a new level due to the possibility of the automated formation of micro-supercapacitors (including flexible, stretchable, wearable) with the required type of geometric implementation, to reduce time and labour costs for their creation, and to expand the prospects of their commercialization and widespread use. Within the framework of this review, we have focused on the consideration of the key commonly used supercapacitor electrode materials and highlighted examples of their successful printing in the process of assembling miniature energy storage devices.

Direct Ink Writing of Pickering Emulsions Generates Ultralight Conducting Polymer Foams with Hierarchical Structure and Multifunctionality

Porous materials with multiple hierarchy levels can be useful as lightweight engineering structures, biomedical implants, flexible functional devices, and thermal insulators. Numerous routes have integrated bottom-up and top-down approaches for the generation of engineering materials with lightweight nature, complex structures, and excellent mechanical properties. It nonetheless remains challenging to generate ultralight porous materials with hierarchical architectures and multi-functionality. Here, the combined strategy based on Pickering emulsions and additive manufacturing leads to the development of ultralight conducting polymer foams with hierarchical pores and multifunctional performance. Direct writing of the emulsified inks consisting of the nano-oxidant-hydrated vanadium pentoxide nanowires-generated free-standing scaffolds, which are stabilized by the interfacial organization of the nanowires into network structures. The following in situ oxidative polymerization transforms the nano-oxidant scaffolds into foams consisting of a typical conducting polymer-polyaniline. The lightweight polyaniline foams featured by hierarchical pores and high surface areas show excellent performances in the applications of supercapacitor electrodes, planar micro-supercapacitors, and gas sensors. This emerging technology demonstrates the great potential of a combination of additive manufacturing with complex fluids for the generation of functional solids with lightweight nature and adjustable structure-function relationships.

Padinjareveetil AK, Pumera M. Edges of Layered FePSe3 Exhibit Increased Electrochemical and Electrocatalytic Activity Compared to Basal Planes

Transition metal trichalcogenphosphites (MPX₃), belonging to the class of 2D materials, are potentially viable electrocatalysts for the hydrogen evolution reaction (HER). Many 2D and layered materials exhibit different magnitudes of electrochemical and electrocatalytic activity at their edge and basal sites. To find out whether edges or basal planes are the primary sites for catalytic processes at these compounds, we studied the local electrochemical and electrocatalytic activity of FePSe₃, an MPX₃ representative that was previously found to be catalytically active. Using scanning electrochemical microscopy, we discovered that electrochemical processes and the HER are occurring at an increased rate at edge-like defects of FePSe₃ crystals. We correlate our observations using optical microscopy, confocal laser scanning microscopy, scanning electron microscopy, and electron-dispersive X-ray spectroscopy. These findings have profound implications for the application of these materials for electrochemistry as well as for understanding general rules governing the electrochemical performance of layered compounds.

Hydrogen Evolution Reaction Performance of Ni-Co-Coated Graphene-Based 3D Printed Electrodes

Additive manufacturing has been a very promising topic in recent years for research and development studies and industrial applications. Its electrochemical applications are very popular due to the cost-effective rapid production from the environmentally friendly method. In this study, three-dimensional (3D) printed electrodes are prepared by Ni and Co coatings in different molar ratios. Different Ni/Co molar ratios (x:y) of the Ni/Co/x:y alloys are prepared as 1:1, 1:4, and 4:1 and they are named Ni/Co/1:1, Ni/Co/4:1, and Ni/Co/1:4, respectively. According to the results, when the 3D electrode samples are coated with Ni and Co at different molar ratios, the kinetic performance of the NiCo-coated 3D electrode samples for hydrogen evolution reaction is enhanced compared to that of the uncoated 3D electrode sample. The results indicate that the Ni/Co/1:4-coated 3D electrode has the highest kinetic activity for hydrogen evolution reactions (HERs). The calculated Tafel's slope and overpotential value (η₁₀) for HER are determined as 164.65 mV/dec and 101.92 mV, respectively. Moreover, the Ni/Co/1:4-coated 3D electrode has an 81.2% higher current density than the other electrode. It is observed that the 3D printing of the electrochemical electrodes is very promising when they are coated with Ni-Co metals in different ratios. This study provides a new perspective on the use of 3D printed electrodes for high-performance water electrolysis.

RGO nanosheet wrapped β-phase NiCu2S nanorods for advanced supercapacitor applications

A new integration strategy of transition metal sulfide with carbon-based materials is used to boost its catalytic property and electrochemical performances in supercapacitor application. Herein, crystalline reduced graphene oxide (rGO) wrapped ternary metal sulfide nanorod composites with different rGO ratios are synthesized using hydrothermal technique and are compared for their physical, chemical, and electrochemical performances. It is found that their properties are tuned by the weight ratios of rGO. The electrochemical investigations reveal that β-NiCu₂S/rGO nanocomposite electrode with 0.15 wt.% of rGO is found to possess maximum specific capacitance of 1583 F g^-1 at current density of 15 mA g^-1 in aqueous electrolyte medium. The same electrode shows excellent cycling stability with capacitance retention of 89% after 5000 charging/discharging cycles. The reproducibility test performed on NiCu₂S/rGO nanocomposite electrode with 0.15 wt.% of rGO indicates that it has high reproducible capacitive response and rate capability. Thus, the present work demonstrates that the β-NiCu₂S/rGO nanocomposite can serve as a potential electrode material for developing supercapacitor energy storage system.

COF-Based Electrodes with Vertically Supported Tentacle Array for Ultrahigh Stability Flexible Energy Storage

As an emerging porous crystal polymer, covalent organic frameworks (COFs) possess unique characteristics, such as high porosity, excellent stability, diverse topologies, designable open channels, and functional tunability. However, limited by the solid powder form, most COFs display low active site utilization and weak binding force with the current collector. In this pioneering research, we integrate redox-active COFs onto carbon fiber surfaces (AC-COFs) via strong covalent bridging. The 2,6-diaminoanthraquinone (DAAQ) pillars embedded on the carbon fiber surface are the key to precisely controlling the growth direction of COFs. The obtained tentacle-like array vertically supported on the surface of the carbon fiber can effectively induce charge transfer and prevent COFs from aggregating/collapsing. The strong covalent coupling and increase of accessible active sites contributed to the high specific capacitance of AC-COFs electrode (1034 mF cm^-2). In addition, the COF-based flexible electrode retains an initial capacitance of 98% after 20000 charge-discharge cycles. The flexible all-solid-state symmetric supercapacitor is assembled by PVA/H₂SO₄ gel electrolyte with an areal capacitance of 715 mF cm^-2. Besides, a red LED can be easily powered by three-bending AC-COFs//AC-COFs devices. The innovative synthesis strategy opens up new opportunities to develop high-performance flexible energy storage devices based on COFs.

Adjusting the Connection Length of Additively Manufactured Electrodes Changes the Electrochemical and Electroanalytical Performance

Changing the connection length of an additively manufactured electrode (AME) has a significant impact on the electrochemical and electroanalytical response of the system. In the literature, many electrochemical platforms have been produced using additive manufacturing with great variations in how the AME itself is described. It is seen that when measuring the near-ideal outer-sphere redox probe hexaamineruthenium (III) chloride (RuHex), decreasing the AME connection length enhances the heterogeneous electrochemical transfer (HET) rate constant (k0) for the system. At slow scan rates, there is a clear change in the peak-to-peak separation (ΔEp) observed in the RuHex voltammograms, with the ΔEp shifting from 118 ± 5 mV to 291 ± 27 mV for the 10 and 100 mm electrodes, respectively. For the electroanalytical determination of dopamine, no significant difference is noticed at low concentrations between 10- and 100-mm connection length AMEs. However, at concentrations of 1 mM dopamine, the peak oxidation is shifted to significantly higher potentials as the AME connection length is increased, with a shift of 150 mV measured. It is recommended that in future work, all AME dimensions, not just the working electrode head size, is reported along with the resistance measured through electrochemical impedance spectroscopy to allow for appropriate comparisons with other reports in the literature. To produce the best additively manufactured electrochemical systems in the future, researchers should endeavor to use the shortest AME connection lengths that are viable for their designs.

3D Printing for Solid-State Energy Storage

Ever-growing demand to develop satisfactory electrochemical devices has driven cutting-edge research in designing and manufacturing reliable solid-state electrochemical energy storage devices (EESDs). 3D printing, a precise and programmable layer-by-layer manufacturing technology, has drawn substantial attention to build advanced solid-state EESDs and unveil intrinsic charge storage mechanisms. It provides brand-new opportunities as well as some challenges in the field of solid-state energy storage. This review focuses on the topic of 3D printing for solid-state energy storage, which bridges the gap between advanced manufacturing and future EESDs. It starts from a brief introduction followed by an emphasis on 3D printing principles, where basic features of 3D printing and key issues for solid-state energy storage are both reviewed. Recent advances in 3D printed solid-state EESDs including solid-state batteries and solid-state supercapacitors are then summarized. Conclusions and perspectives are also provided regarding the further development of 3D printed solid-state EESDs. It can be expected that advanced 3D printing will significantly promote future evolution of solid-state EESDs.

Recent Advances on 2D Materials towards 3D Printing

In recent years, 2D materials have been implemented in several applications due to their unique and unprecedented properties. Several examples can be named, from the very first, graphene, to transition-metal dichalcogenides (TMDs, e.g., MoS2), two-dimensional inorganic compounds (MXenes), hexagonal boron nitride (h-BN), or black phosphorus (BP). On the other hand, the accessible and low-cost 3D printers and design software converted the 3D printing methods into affordable fabrication tools worldwide. The implementation of this technique for the preparation of new composites based on 2D materials provides an excellent platform for next-generation technologies. This review focuses on the recent advances of 3D printing of the 2D materials family and its applications; the newly created printed materials demonstrated significant advances in sensors, biomedical, and electrical applications.

Celery-derived porous carbon materials for superior performance supercapacitors

Supercapacitors are of paramount importance for next-generation applications, demonstrating high energy output and an ultra-long cycle life, and utilizing green and sustainable materials. Herein, we utilize celery, a common biomass from vegetables, by a facile low-cost pyrolysis and activation method for use in high-voltage, high-energy, and high-power supercapacitors. The as-synthesized hierarchically porous carbon materials with a high surface area of 1612 m2 g-1 and a large quantity of nitrogen and phosphorus heteroatoms exhibit a high specific capacitance of 1002.80 F g-1 at 1 A g-1 and excellent cycling stability of 95.6% even after 10 000 cycles (10 A g-1) in aqueous electrolytes. Moreover, the assembled symmetric cell delivers a high energy density of 32.7 W h kg-1 at 1200 W kg-1 and an ultra-high stability (loss of 4.8% after 10 000 cycles). Therefore, the outstanding electrochemical performance of the materials will be of use in the development of high-performance, green supercapacitors for advanced energy storage systems.

MXene and MoS3- x Coated 3D-Printed Hybrid Electrode for Solid-State Asymmetric Supercapacitor

Recently, 2D nanomaterials such as transition metal carbides or nitrides (MXenes) and transition metal dichalcogenides (TMDs) have attracted ample attention in the field of energy storage devices specifically in supercapacitors (SCs) because of their high metallic conductivity, wide interlayer spacing, large surface area, and 2D layered structures. However, the low potential window (ΔV ≈ 0.6 V) of MXene e.g., Ti₃ C₂ T_x limits the energy density of the SCs. Herein, asymmetric supercapacitors (ASCs) are fabricated by assembling the exfoliated Ti₃ C₂ T_x (Ex-Ti₃ C₂ T_x ) as the negative electrode and transition metal chalcogenide (MoS_{3- x} ) coated 3D-printed nanocarbon framework (MoS_{3- x} @3DnCF) as the positive electrode utilizing polyvinyl alcohol (PVA)/H₂ SO₄ gel electrolyte, which provides a wide ΔV of 1.6 V. The Ex-Ti₃ C₂ T_x possesses wrinkled sheets which prevent the restacking of Ti₃ C₂ T_x 2D layers. The MoS_{3- x} @3DnCF holds a porous structure and offers diffusion-controlled intercalated pseudocapacitance that enhances the overall capacitance. The 3D printing allows a facile fabrication of customized shaped MoS_{3- x} @3DnCF electrodes. Employing the advantages of the 3D-printing facilities, two different ASCs, such as sandwich- and interdigitated-configurations are fabricated. The customized ASCs provide excellent capacitive performance. Such ASCs combining the MXene and electroactive 3D-printed nanocarbon framework can be used as potential energy storage devices in modern electronics.