Electrodeposited Sulfur and CoxS Electrocatalyst on Buckypaper as High-Performance Cathode for Li-S Batteries

Lithium-sulfur batteries(LSBs)are considered as the next generation of advanced rechargeable batteries because of their high energy density.In this study,sulfur and CoxS electrocatalyst are deposited on carbon nanotube buckypaper(S/CoxS/BP)by a facile electrodeposition method and are used as a binder-free high-performance cathode for LSBs.Elemental sulfur is deposited on buckypaper by electrooxidation of a polysulfide solution(-S6^2-).This approach substantially increased the current and time efficiency of sulfur electrochemical deposition on conductive material for LSBs.S/CoxS/BP cathode could deliver an initial discharge capacity as high as 1650 mAh g^-1 at 0.1 C,which is close to the theoretical capacity of sulfur.At current rate of 0.5 C,the S/CoxS/BP has a capacity of 1420 mAh g^-1 at the first cycle and 715 mAh g^-1 after 500 cycles with a fading rate of 0.099%per cycle.The high capacity of S/CoxS/BP is attributed to both the homogeneous dispersion of nanosized sulfur within BP and the presence of CoxS catalyst.The sodium dodecyl sulfate(SDS)pretreatment of BP renders it polarity to bind polysulfides and thus facilitates the good dispersibility of nanosized sulfur within BP.CoxS catalyst accelerates the kinetics of polysulfide conversion and reduces the presence of polysulfide in the cathode,which suppresses the polysulfide diffusion to anode,i.e.,the shuttle effect.The mitigation of the active material loss improves not only the capacity but also the cyclability of S/CoxS/BP.

Nanosphere molecularly imprinted polymers doped with gold nanoparticles for high selectivity molecular sensors

We report the first attempt of using molecularly imprinted polymers （MIPs） in the shape of nanoparticles that were doped with gold nanoparticles （AuNPs） for surface enhanced Raman scattering （SERS）-based sensing of molecular spedes. Specifically, AuNPs doped molecularly imprinted nano-spheres （AuNPs@nanoMIPs） were synthesized by one-pot precipitation polymerization using Sudan IV as the template for the SERS sensing. The AuNPs@nanoMIPs were characterized by various modes of scanning transmission electron microscopy （STEM） that showed the exact location of the AuNPs inside the MIP particles. The effects of Au concentration and solution stirring on the shape and the polydispersity of the particles were studied. Significant enhancement of the Raman signals was observed only when the MIP particles were doped with the AuNPs. The SERS signal improved significantly with increase in the Au concentration inside the AuNPs@nanoMIPs. Selectivity measurements of the Sudan IV imprinted AuNPs@nanoMIPs carried out with different Sudan derivatives showed high selectivity of the AuNPs-doped MIP particles.

Methanol electro-oxidation to formate on iron-substituted lanthanum cobaltite perovskite oxides

Electrochemically producing formate by oxidizing methanol is a promising way to add value to methanol.Noble metal-based electrocatalysts,which have been extensively studied for the methanol oxidation reaction,can catalyze the complete oxidation of methanol to carbon dioxide,but not the mild oxidation to formate.As a result,exploring efficient and earth-abundant electrocatalysts for formate production from methanol is of interest.Herein,we present the electro-oxidation of methanol to formate,catalyzed by iron-substituted lanthanum cobaltite(LaCo_(1-x)Fe_(x)O_(3)).The Fe/Co ratio in the oxides greatly influences the activity and selectivity.This effect is attributed to the higher affinity of Fe and Co to the two reactants:CH3OH and OH,respectively.Because a balance between these affinities is favored,LaCo_(0.5)Fe_(0.5)O_(3) shows the highest formate production rate,at 24.5 mmol h^(-1) g_(oxide)^(-1),and a relatively high Faradaic efficiency of 44.4%in a series of(LaCo_(1-x)Fe_(x)O_(3))samples(x=0.00,0.25,0.50,0.75,1.00)at 1.6 V versus a reversible hydrogen electrode.

Effect of matrix-nanoparticle interactions on recognition of aryldiazonium nanoparticle-imprinted matrices

The selective recognition of nanoparticles (NPs) can be achieved by nanoparticle-imprinted matrices (NAIMs),where NPs are imprinted in a matrix followed by their removal to form voids that can reuptake the original NPs.The recognition depends on supramolecular interactions between the matrix and the shell of the NPs,as well as on the geometrical suitability of the imprinted voids to accommodate the NPs.Here,gold NPs stabilized with citrate (AuNPs-cit) were preadsorbed onto a conductive surface followed by electrografting of p-aryldiazonium salts (ADS) with different functional groups.The thickness of the matrix was carefully controlled by altering the scan number.The AuNPs-cit were removed by electrochemical dissolution.The recognition of the NAIMs was determined by the reuptake of the original AuNPs-cit by the imprinted voids.We found that the recognition efficiency is a function of the thickness of the NAIM layer and is sensitive to the chemical structure of the matrix.Specifically,a subtle change of the functional group of the p-aryldiazonium building block,which was varied from an ether to an ester,significantly affected the recognition of the NPs.