Hydrothermal synthesis and electrochemical sensing properties of copper vanadate nanocrystals with controlled morphologies

Morphology-controlled synthesis of copper vanadate nanocrystals is of great significance in electrochemical sensing applications.A facile hydrothermal process for synthesizing copper vanadate nanocrystals with various morphologies(e.g.,nanoparticles,nanobelts and nanoflowers)was reported.Phase,morphology and electrochemical performance of the as-synthesized copper vanadate nanocrystals were characterized by X-ray diffraction(XRD),scanning electron microscope(SEM)and cyclic-voltammogram(CV)techniques.The results revealed that the morphologies of the Cu3V2O7(OH)2·2H2O(CVOH)nanocrystals could be controlled by changing copper salts,surfactants and pH values.The CVOH samples showed enhanced electrochemical response to ascorbic acid.Comparatively,the CVOH nanobelts had the higher electrochemical sensing performance than those of CVOH nanoparticles and nanoflowers.The CVOH-nanobelts-modified GCEs had a linear relationship between the peak currents in their CVs and ascorbic acid concentration.The CVOH nanocrystals can be used as potential electrochemical active materials for the determination of ascorbic acid.

Robust copper nanocrystal/nitrogen-doped carbon monoliths as carbon monoxide-resistant electrodes for methanol oxidation reaction

Noble metal-based electrocatalysts present high activities for methanol oxidation reaction(MOR),but are limited by their high cost,low stability and poor resistance to carbon monoxide(CO) poisoning.The development of active and stable non-noble metal electrocatalysts for MOR is desired,but remains a challenge.Herein,we report a simple strategy to make copper nanocrystal/nitrogen-doped carbon(Cu/N-C)monoliths,which can serve as active and robust electrodes for MOR.Copper nanocrystals were electrochemically deposited onto a conductive polyaniline hydrogel and calcined to form Cu/N-C monolith,where the active copper nanocrystals are protected by nitrogen-doped carbon.Owing to their extremely high electrical conductivity(1.25 × 10^(5) S cm^(-1)) and mechanical robustness,these Cu/N-C monoliths can be directly used as electrodes for MOR,without using substrates or additives.The optimal Cu/N-C(FT)@500 monolith shows a high MOR activity of 189 mA cm^(-2) at 0.6 V vs.SCE in alkaline methanol solution,superior to most of reported Cu-based MOR catalysts.Cu/N-C(FT)@500 also presents a better stability than Pt/C catalyst in the long-term MOR test at high current densities.Upon carbon monoxide(CO) poisoning,Cu/N-C(FT)@500 retains 96% of its MOR activity,far exceeding the performance of Pt/C catalyst(61% retention).Owing to its facile synthesis,outstanding activity,high stability and mechanical robustness,Cu/N-C(FT)@500 monolith is promising as a low-cost,efficient and CO-resistant electrocatalyst for MOR.

Precipitation of flaky moolooite and its thermal decomposition

Moolooite particles with flaky morphology were synthesized by mixing dilute solutions of copper nitrate and sodium oxalate in the presence of citric acid. Solution p H value, citric acid concentration, and stirring were found to have large effect on the shape of the precipitated particles. Under the stirring, the radial area of flaky moolooite particles was enlarged and extended to become a thinner and larger flake. This is ascribed to growth promotion caused by the selective absorption of citric ligands onto a particular crystalline surface of the moolooite particles. Flaky shape of the moolooite particles tended to become spherical and disappeared completely when decomposed under an Ar atmosphere, leading to the formation of large porous aggregated particles composed of many tiny nanosized copper crystals.

Quaternized chitosan-assisted in situ synthesized CuS/cellulose nanofibers conductive paper for flexible electrode

Cellulose nanofibers(CNF)are considered to be a potential substrate of energy material for energy storage devices due to the foldable,lightweight,recyclable and environmentally friendly feature.However,the energy materials tend to distribute unevenly or fall off from CNF easily,resulting in the decrease of the devices’overall performance.Here,for the first time,we used quaternized chitosan(QCS)as stabilizer and adhesive to in situ synthesize and deposite copper sulfide nanocrystals(CuS-NCs)on CNF and further obtained the conductive paper for flexible supercapacitors.In the presence of QCS,CuS-NCs deposited in situ on CNF can be capped and stabilized by the QCS molecular chains for uniform distribution,which is conducive to the capacitive behavior and electrochemical stability of composite paper.The result shows that the specific capacitance of the composite paper was as high as 314.3 F/g at a current density of 1 A/g,a high rate capacitance of 252.6 F/g was achieved even at a high current density of 10 A/g.It reveals that the composite paper exhibited better electrochemical performance than many other CuS-based electrode materials for supercapacitor.More importantly,the composite paper performed well in various folding state without changing much electrochemical performance.Therefore,this work provides a novel strategy to in situ fabricate paper-based electrode for nextgeneration flexible energy-storage system.