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A high-performance V4C3TX@NiO-RGO//DRGO asymmetric supercapacitor device is assembled based on a 3D free-standing V4C3TX@NiO-RGO hydrogel as a positive electrode and a 3D DRGO hydrogel as a negative electrode.

Design and engineering of effective electrode catalysts represents a critical first step for hydrogen production by electrochemical water splitting. Nanocomposites based on ruthenium atomically dispersed within a carbon scaffold have emerged as viable candidates. In the present study, ruthenium metal centers are atomically embedded within graphitic carbon nitride/reduced graphene oxide nanosheets by thermal refluxing. Subsequent chemical reduction/oxidation leads to ready manipulation of the ruthenium valence state, as evidenced in microscopic and spectroscopic measurements, and hence enhancement/diminishment of the electrocatalytic activity towards hydrogen evolution reaction in both acidic and alkaline media. This is largely ascribed to the increased/reduced contribution of the Ru valence electrons to the density of state near the Fermi level which dictates the binding and reduction of hydrogen. Results from this study highlight the significance of the valence state of metal centers in the manipulation and optimization of the catalytic performance of single atom catalysts.

Asymmetric supercapacitors (ASCs) based on a battery-type anode and a capacitive-type cathode have been attracting extensive interest because of their high energy density. Herein, NiO nanosheets are hydrothermally deposited onto a V4C3TX substrate, which are then assembled into a 3D porous heterostructure hydrogel through a graphene oxide-assisted self-convergence hydrothermal process at low temperatures. The resultant hierarchical V4C3TX@NiO-reduced graphene oxide (RGO) hydrogel exhibits an ultrahigh specific capacitance up to 1014.5 F g− 1 at 1 A g− 1. Separately, a defective reduced graphene oxide (DRGO) hydrogel is prepared by a cost-effective hydrothermal procedure followed by cobalt-catalyzed gasification, which shows a higher specific capacitance (258 F g− 1 at 1 A g− 1) than untreated RGO hydrogel (176 F g− 1). These two electrodes are then assembled into an ASC, the device features a stable operating voltage of 1.8 V, a maximum energy density of 86.22 Wh kg− 1 at 900 W kg− 1, along with good cycling stability at 96.4% capacitance retention after 10,000 cycles at 10 A g− 1. This work highlights the unique potential of MXenes-based materials for the construction of high-performance ASCs.

Metal phosphates, such as LiFePO4 (LFP), have been attracting extensive attention as electrode materials for next-generation rechargeable metal-ion batteries (MIBs), due to their high theoretical capacity, good chemical stability, long lifespan, and natural abundance. In this review, the recent progress of the design and engineering of metal phosphate-based electrode materials for MIBs is summarized. Specifically, the survey will focus on three types of phosphates, monometallic phosphates, bimetallic phosphates, and multi-metal phosphates, within the context of their intrinsic structure and corresponding electrochemical performance. A range of experimental variables will be carefully analyzed, such as sample synthesis, crystal structure, and electrochemical reaction mechanism, in conjunction with theoretical calculations. The applications of these materials as MIB electrodes are then featured for diverse MIBs, such as lithium-ion battery, sodium-ion batteries, potassium-ion batteries, calcium-ion batteries, and magnesium-ion batteries. We conclude the review with a perspective where the promises and challenges of phosphate-based electrodes for MIBs are highlighted, along with future research directions.

Copper compounds have been extensively investigated for diverse applications. However, studies of cuprous hydroxide (CuOH) have been scarce, due to structural metastability. Herein, a facile, wet-chemistry procedure is reported for the preparation of stable CuOH nanostructures via deliberate functionalization with select organic ligands, such as acetylene and mercapto derivatives. The resulting nanostructures are found to exhibit a nanoribbon morphology consisting of small nanocrystals embedded within a largely amorphous nanosheet-like scaffold. The acetylene derivatives are found to anchor onto the CuOH forming Cu-Cࣽ linkages, whereas Cu-S- interfacial bonds are formed with the mercapto ligands. Effective electronic coupling occurs at the ligand-core interface in the former, in contrast to mostly non-conjugated interfacial bonds in the latter, as manifested in spectroscopic measurements and confirmed in theoretical studies based on first principles calculations. Notably, the acetylene-capped CuOH nanostructures exhibit markedly enhanced photodynamic activity in the inhibition of bacteria growth, as compared to the mercapto-capped counterparts, due to a reduced material bandgap and effective photocatalytic generation of reactive oxygen species. Results from this study demonstrate that deliberate structural engineering with select organic ligands is an effective strategy in the stabilization and functionalization of CuOH nanostructures, a critical first step in exploring their diverse applications. This article is protected by copyright. All rights reserved.

With the rapid development of wireless telecommunication technologies, it is of fundamental and technological significance to design and engineer high-performance shielding materials against electromagnetic interference (EMI). Herein, a three-step procedure is developed to produce hydrophobic, flexible nanofiber films for EMI shielding and pressure sensing based on hydrolysate of waste leather scraps (HWLS): (i) electrospinning preparation of HWLS/polyacrylonitrile (PAN) nanofiber films, (ii) adsorption of silver nanowires (AgNWs) onto HWLS/PAN nanofiber films, and (iii) coating of HWLS/PAN/AgNWs nanofiber films with polydimethylsiloxane (PDMS). Scanning electron microscopy studies show that AgNWs are interweaved with HWLS/PAN nanofibers to form a conductive network, exhibiting an electrical conductivity of 10

Nano research 14(8), 2762 – 2769 (2020). doi:10.1007/s12274-020-3281-z, In this work, we demonstrate the power of a simple top-down electrochemical erosion approach to obtain Pt nanoparticle with controlled shapes and sizes (in the range from ∼ 2 to ∼ 10 nm). Carbon supported nanoparticles with narrow size distributions have been synthesized by applying an alternating voltage to macroscopic bulk platinum structures, such as disks or wires. Without using any surfactants, the size and shape of the particles can be changed by adjusting simple parameters such as the applied potential, frequency and electrolyte composition. For instance, application of a sinusoidal AC voltage with lower frequencies results in cubic nanoparticles; whereas higher frequencies lead to predominantly spherical nanoparticles. On the other hand, the amplitude of the sinusoidal signal was found to affect the particle size; the lower the amplitude of the applied AC signal, the smaller the resulting particle size. Pt/C catalysts prepared by this approach showed 0.76 A/mg mass activity towards the oxygen reduction reaction which is ∼ 2 times higher than the state-of-the-art commercial Pt/C catalyst (0.42 A/mg) from Tanaka. In addition to this, we discussed the mechanistic insights about the nanoparticle formation pathways., Published by Springer, New York, NY [u.a.]