Interfacial and Vacancies Engineering of Copper Nickel Sulfide for Enhanced Oxygen Reduction and Alcohols Oxidation Activity

Rational design and construction of highly efficient nonprecious electrocatalysts for oxygen reduction and alcohols oxidation reactions(ORR,AOR)are extremely vital for the development of direct oxidation alkaline fuel cells,metal-air batteries,and water electrolysis system involving hydrogen and value-added organic products generation,but they remain a great challenge.Herein,a bifunctional electrocatalyst is prepared by anchoring CuS/NiS_(2)nanoparticles with abundant heterointerfaces and sulfur vacancies on graphene(Cu_(1)Ni_(2)-S/G)for ORR and AOR.Benefiting from the synergistic effects between strong interfacial coupling and regulation of the sulfur vacancies,Cu_(1)Ni_(2)-S/G achieves dramatically enhanced ORR activity with long term stability.Meanwhile,when ethanol is utilized as an oxidant for AOR,an ultralow potential(1.37 V)at a current density of 10 mA cm-2 is achieved,simultaneously delivering a high Faradaic efficiency of 96%for ethyl acetate production.Cu_(1)Ni_(2)-S/G also exhibits catalytic activity for other alcohols electrooxidation process,indicating its multifunctionality.This work not only highlights a viable strategy for tailoring catalytic activity through the synergetic combination of interfacial and vacancies engineering,but also opens up new avenues for the construction of a self-driven biomass electrocatalysis system for the generation of value-added organic products and hydrogen under ambient conditions.

Boosting the electrochemical performance and reliability of conducting polyme microelectrode via intermediate graphene for on-chip asymmetric micro-supercapacitor

High-performance anode is hurdle for on-chip planar microsupercapacitor(MSC).Polypyrrole(PPy)is a highly attractive pseudocapacitive material,but its low cycling stability,and low adhesion with current collector hinder its practicability.Herein we propose one-prong generic strategy to boost the cycling stability of PPy.For our strategy,the electrochemical deposition of multilayered reduced graphene oxide(rGO)on micropatterned Au is utilized,and the resultant rGO@Au pattern is then used for growing highly porous PPy nanostructures by facile electrochemical polymerization.The fabricated PPy anode on rGO@Au has quasi rectangular cyclic voltammetry curves up to-0.7 V and exceptional cycling stability,retaining82%of capacitance after 10,000 charge/discharge cycles in 2 M KCl electrolyte.The outstanding reliability of PPy on rGO@Au is due to the flexibility of rGO,accommodating structural pulverization and providing a promising background for the nucleation of highly porous nanostructure.Further,an all-polymer based asymmetric aqueous MSC(AMSC)is constructed with PPy anode and PEDOT cathode,which exhibited excellent electrochemical performance compared with conventional symmetric MSCs based on conducting polymers.The constructed AMSC delivered a maximum areal capacitance of 15.9 m F cm^-2(99.3 F cm^-3),high specific energy and power densities of 4.3μWh cm^-2(27.03 mWh cm^-3)and 0.36 W cm^-2(0.68 W cm^-3)at 1.4 V,respectively.The enhanced electrochemical performances can be illustrated by nucleation mechanism,in which surface topology of r GO generates a promising background for nucleation and electrochemical growth of nanoporous pseudocapacitive conducting polymers with superior interfacial contact and improved surface area.

Macroscopic synthesis of ultrafine N–doped carbon nanofibers for superior capacitive energy storage

Carbon nanofibers(CNFs)with excellent electric conductivity and high surface area have attracted immense research interests in supercapacitors.However,the macroscopic production of CNFs still remains a great challenge.Herein,ultrafine N–doped CNFs(N–CNFs)with a diameter of$20 nm are synthesized through a simple and scalable sol-gel method based on the self-assembly of phenolic resin and cetyltrimethylammonium bromide.When employed in aqueous supercapacitors,the obtained activated N–CNFs manifest a high gravimetric/areal capacitance(380 Fg-1/1.7 Fcm-2)as well as outstanding rate capability and cycling stability.Besides,the activated N–CNFs also demonstrate excellent capacitive performance(330 Fg-1)in flexible quasi-solid-state supercapacitors.The remarkable electrochemical performance as well as the easy and scalable synthesis makes the N–CNFs a highly promising electrode material for supercapacitors.

MoS2/MnO2 heterostructured nanodevices for electro- chemical energy storage

Hybrid or composite heterostructured electrode materials have been widely studied for their potential application in electrochemical energy storage. Whereas their physical or chemical properties could be affected significantly by modulating the heterogeneous interface, the underlying mechanisms are not yet fully understood. In this work, we fabricated an electrochemical energy storage device with a MoS2 nanosheet/MnO2 nanowire heterostructure and designed two charge/discharge channels to study the effect of the heterogeneous interface on the energy storage performances. Electrochemical measurements show that a capadty improvement of over 50% is achieved when the metal current collector was in contact with the MnO2 instead of the MoS2 side. We propose that this enhancement is due to the unidirectional conductivity of the MoS2/MnO2 heterogeneous interface, resulting from the unimpeded electrical transport in the MnO2-MoS2 channel along with the blocking effect on the electron transport in the MoS2-MnO2 channel, which leads to reaction kinetics optimization. The present study thus provides important insights that will improve our understanding of heterostructured electrode materials for electrochemical energy storage.

Activated carbon clothes for wide-voltage high-energy-density aqueous symmetric supercapacitors

Commercial carbon clothes have the potential to be utilized as supercapacitor electrodes due to their low cost and high conductivity.However,the negligible surface area of the carbon clothes serves as a serious impediment to their utilization.Herein,we report a facile calcination activation method for carbon cloths to realize remarkable comprehensive electrochemical performance.The activated carbon cloths deliver a high areal capacitance(1700 mF/cm^2),good rate capability,and stable cycling performance up to 20,000 cycles.Owing to the stability in the wide potential window,a designed symmetric capacitor can function in a cell voltage of 2.0 V and delivers high volumetric and gravimetric energy densities of 7.62 mWh/cm^3 and 18.2 Wh/kg,respectively.The remarkable electrochemical performance is attributed to rich microporosity with high surface area,superior electrolyte wettability,and stability in wide potential window.