Electrospun polyporous VN nanofibers for symmetric all-solid-state supercapacitors

To promote the energy density of symmetric all-solid-state supercapacitors(SCs),efforts have been dedicated to searching for high-performance electrode materials recently. In this paper,vanadium nitride(VN) nanofibers with mesoporous structure have been fabricated by a facile electrospinning method. Their crystal structures and morphology features were characterized by X-ray diffraction,scanning electron microscopy,and transmission electron microscopy. The mesoporous structure of VN nanofibers,which can provide short electrolyte diffusion routes and conducting electron transport pathways,is beneficial to their performance as a supercapacitor electrode. Under a stable electrochemical window of 1.0 V,VN nanofibers possess an excellent mass specific capacitance of 110.8 F/g at a scan rate of 5 mV/s. Moreover,the VN nanofibers were further assembled into symmetric all-solid-state SCs,achieving a high energy density of 0.89 mW·h/cm^3 and a high power density of 0.016 W/cm^3 over an operating potential range from 0 to 1.0 V. These results demonstrate that VN nanofibers could be potentially used for energy storage devices.

Layer-structured Cr/Cr_(x)N coating via electroplating-based nitridation achieving high deuterium resistance as the hydrogen permeation barrier

Hydrogen isotope permeation through structural materials is a key issue for developing nuclear fusion energy,which will cause fuel loss and radioactive pollution.Developing ceramic coatings with high thermal shock and hydrogen resistance is an effective strategy to solve this issue.In this work,a layer-structured Cr/Cr_(x)N coating was successfully fabricated by a facile electroplatingbased nitridation technique,which is easy,facile,and applicable to coating complex-shaped substrates.The Cr/Cr_(x)N coating,composed of a bottom Fe/Cr interdiffusion zone,a middle Cr layer,and a top Cr_(x)N layer,exhibits high bonding strength,high anti-thermal-shock ability,and high deuterium permeation resistance.Its bonding strength achieves 43.6 MPa.The Cr/Cr_(x)N coating remains intact even after suffering 300 thermal shock cycles under a 600℃–water condition.Through optimizing the nitridation temperature,the Cr/Cr_(x)N coating achieves a deuterium permeation reduction factor(PRF)as high as 3599 at 500℃.Considering its scalable fabrication technique and considerable properties,the developed Cr/Cr_(x)N coating may serve as a novel high-performance hydrogen permeation barrier in various fields.

Direct writing of silver microfiber with precise control on patterning for robust and flexible ultrahigh-performance transparent conductor

Ultrafine silver fiber is an alternative to commercial indium tin oxide(ITO) as a new-generation flexible transparent conductor that can be used in flexible electronics.However,its primary limitation is the unrepeatable optoelectronic properties due to the disordered distribution of silver fibers.In this work,we report the in-situ direct writing of the silver microfiber pattern with high conductivity and transparency to attain a flexible transparent conductor.The silver network is composed of silver microfibers,which can be artificially designed and regularly patterned under the precise control of the fiber position and shape;this is crucial for regulating its optoelectronic properties.Herein,a high-performance conductor is achieved in the silver network with high stability.This novel conductor has a sheet resistance of 2 Ω sq-1at 90% transparency,which corre sponds to a high Figure of merit σdc/σopt=1742.The in-situ direct writing technique developed here is distinct from other fabrication methods because it requires no transfer steps,templates or heating.Further,this silver network is integrated into a light-printable rewritable device,and can be used as a wearable heater;this heater when driven by a 1.5 V battery attains a temperature of up to 55.6℃.Therefore,in-situ direct writing is expected to offer a new platform for facile,scalable,and ultralow-cost production of high-performance metal networks for flexible transparent conductors.