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Detection of individual nanoparticles is of high importance to basic science as well as to applied one, i.e., for remediation efforts. Electrochemistry was shown previously to play an important role in detection, counting and measuring individual nanoparticles. Here we show that individual molybdenum nanoparticles can be detected and counted by chronoamperometry upon their impact on the carbon electrode surface. The size determination of individual nanoparticles by electrochemical measurement is consistent with the size determination by scanning electron microscopy. Keywords: Individual nanoparticle detection, Metal, Dissolution, Chronoamperometry, Anodic particle coulometry

MoS2 nanosheets of one to few layer thickness present novel electronic and enhanced catalytic properties with respect to the bulk material. Here we show that a simple and highly scalable ball-milling procedure can lead to significant improvements of the electrochemical and catalytic properties of the bulk natural MoS2. We characterized the material before and after the milling process by means of scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy in order to evaluate morphological and chemical features. We investigated the electrochemical properties by means of voltammetry techniques to monitor the electron transfer with [Fe(CN)6]4−/3− redox probe and the catalytic properties by monitoring the electrochemical hydrogen evolution reaction (HER). A significant overpotential lowering of about 210 mV is obtained for the HER by the ball-milled material when compared to bulk materials. This has a huge potential for the lowering of the energy consumption during hydrogen evolution. Ball-milling offers highly scalable dry method for large scale production of electrocatalyst with enhanced properties. Keywords: Molybdenum sulfide, Ball-milling, Hydrogen evolution reaction

Graphene related materials are widely expected to play a major role as materials for the construction of supercapacitors. We demonstrate here that graphene oxides prepared by various well-established methods exhibit dramatically different capacitances. We exfoliated graphite oxide sonographically to graphene oxide (GO) and we reduced GO by chemical or electrochemical means to chemically reduced graphene oxide (CRGO) and electrochemically reduced graphene oxide (ERGO); in addition, graphite oxide was thermally exfoliated leading to thermally reduced graphene oxide (TRGO). We found clear dependence of weight specific capacitance upon amount of oxygen containing groups presented on the surface of these graphenes. GO exhibits the lowest and TRGO the highest values of weight specific capacitance. Keywords: Graphene, Capacitance, Graphene oxide