Metal-Oxide Decorated Multilayered Three-Dimensional (3D) Porous Carbon Thin Films for Supercapacitor Electrodes

A Review on Advanced Manufacturing for Hydrogen Storage Applications

Hydrogen is a notoriously difficult substance to store yet has endless energy applications. Thus, the study of long-term hydrogen storage, and high-pressure bulk hydrogen storage have been the subject of much research in the last several years. To create a research path forward, it is important to know what research has already been done, and what is already known about hydrogen storage. In this review, several approaches to hydrogen storage are addressed, including high-pressure storage, cryogenic liquid hydrogen storage, and metal hydride absorption. Challenges and advantages are offered based on reported research findings. Since the project looks closely at advanced manufacturing, techniques for the same are outlined as well. There are seven main categories into which most rapid prototyping styles fall. Each is briefly explained and illustrated as well as some generally accepted advantages and drawbacks to each style. An overview of hydrogen adsorption on metal hydrides, carbon fibers, and carbon nanotubes are presented. The hydrogen storage capacities of these materials are discussed as well as the differing conditions in which the adsorption was performed under. Concepts regarding storage shape and materials accompanied by smaller-scale advanced manufacturing options for hydrogen storage are also presented.

Carbon Transition-metal Oxide Electrodes: Understanding the Role of Surface Engineering for High Energy Density Supercapacitors

Supercapacitors store electrical energy by ion adsorption at the interface of the electrode-electrolyte (electric double layer capacitance, EDLC) or through faradaic process involving direct transfer of electrons via oxidation/reduction reactions at one electrode to the other (pseudocapacitance). The present minireview describes the recent developments and progress of carbon-transition metal oxides (C-TMO) hybrid materials that show great promise as an efficient electrode towards supercapacitors among various material types. The review describes the synthetic methods and electrode preparation techniques along with the changes in the physical and chemical properties of each component in the hybrid materials. The critical factors in deriving both EDLC and pseudocapacitance storage mechanisms are also identified in the hope of pointing to the successful hybrid design principles. For example, a robust carbon-metal oxide interaction was identified as most important in facilitating the charge transfer process and activating high energy storage mechanism, and thus methodologies to establish a strong carbon-metal oxide contact are discussed. Finally, this article concludes with suggestions for the future development of the fabrication of high-performance C-TMO hybrid supercapacitor electrodes.

High Entropy Oxides-A Cost-Effective Catalyst for the Growth of High Yield Carbon Nanotubes and Their Energy Applications

This report anticipates a thorough strategy for the utilization of high entropy oxide (HEO) nanoparticles (1) as a cost-effective catalyst for the growth of high yield carbon nanotubes (CNTs), resulting in HEO-CNT nanocomposites, and (2) the implementation of HEO-CNT nanocomposites for energy applications such as electrochemical capacitors (ECs). In the first step, HEO nanoparticles were synthesized by a simple sol-gel autocombustion method and then the as-synthesized HEO nanoparticles were ground and used as the catalyst for the growth of CNTs by chemical vapor deposition technique. The as-grown CNTs (HEO-CNT nanocomposite) exhibited unexpectedly high yield, a superior specific surface area of ∼151 m² g^-1, and encapsulation and diffusion of the catalyst throughout the HEO-CNT nanocomposite, providing remarkably high mechanical strength, which make them a promising candidate for energy applications. To study the electrochemical activity of the HEO-CNT nanocomposite, half-cell and full-cell ECs were assembled in different electrolytes. Stupendously, a complete 100% capacitance retention and a Coulombic efficiency up to 15 000 cycles were realized for the HEO-CNT nanocomposite-based full-cell EC assembled in the polyvinyl alcohol/H₂SO₄ hydrogel electrolyte. Additionally, a high specific capacitance value of 286.0 F g^-1 at a scan rate of 10 mV s^-1 for the HEO-CNT nanocomposite-based full-cell EC assembled in the [BMIM][TFSI] electrolyte with a wide potential window of 2.5 V is reported. Also, high energy density and power density of ∼217 W h kg^-1 and ∼24 521 W kg^-1, respectively, are reported. Furthermore, the HEO-CNT nanocomposite-based full-cell EC assembled in the [BMIM][TFSI] electrolyte can successfully light up a red light-emitting diode, demonstrating great potential of the HEO-CNT nanocomposite in the various energy applications.

Three-dimensional porous carbonaceous network with in-situ entrapped metallic cobalt for supercapacitor application

Herein, we outline the fabrication of highly porous three-dimensional carbon-fiber network anchored with uniform metallic cobalt (Co) via electrospinning and subsequent post-modification approaches. First, cobalt acetate solution saturated electrospun polyacrylonitrile (PAN) nanofibrous mat was subjected to sodium borohydride (NaBH₄) solution which results in the fabrication of three dimensional (3D) hierarchical multilayer network. Restructuring of the 2D mat into multilayered sponges with metal particles entrapment is attributed to the in-situ generated hydrogen gas into the interconnected pores of the fibrous network simultaneous with reduction of cobalt salt into metallic cobalt by NaBH₄. The resulting mesh was stabilized and carbonization at inert atmosphere to obtain metallic cobalt (Co) embedded 3D carbon nanofibrous networks (Co@3D-CNFs). Physicochemical characterization and electrochemical analysis were performed. Results show carbon network was found to be expanded with bubbling like structures often embedded metallic Co nanoparticles. X-ray diffraction (XRD) pattern confirms the existence of the metallic cobalt particles on the carbon fiber networks. Furthermore, we establish a resulting composite (Co@3D-CNFs) identify the enhanced electrochemical performance having specific capacitance 762 F g^-1 compared to 173 and 180 F g^-1 for corresponding @3D-CNFs and 2D carbon nanofiber network with cobalt doped (Co@2D-CNFs) counterparts, respectively. The assembled Co2@3D-CNFs//NGH ASC device exhibits a high energy density 24.6 W h Kg^-1 at 797 W kg^-1 power density with an operating voltage of 1.6 V (vs Ag/AgCl). The device further shows good capacitance retention (90.1%) after 5000 cycles. This research shows the simple and cost-effective strategy to make metallic particles embedded 3D porous carbonaceous electrode materials which can have great potential for energy storage application.

Facile reduction of para-nitrophenols: catalytic efficiency of silver nanoferns in batch and continuous flow reactors

Catalytic application of Ag-nanoferns grown over carbon microfibers by electrodeposition and compatible reactor design for batch and continuous flow operations.