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Platinum is one of the most effective electro catalysts for PEMFCs (proton exchange membrane fuel cells), but because of its prohibitive price, the use of this metal in industrial purposes is limited. As a consequence, during last years, several materials have been investigated, in order to obtain an efficient catalyst for both ORR (oxygen reduction reaction) and HOR (hydrogen oxidation reaction), which can replace the expensive platinum but preserving the same properties: high electrical conductivity, structural stability and good corrosion resistance. Moreover, one of the most important parameters for catalyst materials is the electrochemical surface area (real surface area), which has a strong influence on the reaction rate and also on the current density.
CNFs (carbon nanofibers) are considered to be a promising catalyst support material due to their unique characteristics, excellent mechanical, electrical and structural properties, high surface area and nevertheless, good interaction with platinum particles.
The possibility of preparing CNFs decorated with platinum by electrochemical methods was tested, using a hexachloroplatinic solution bath. The experiments were carried out with the aid of a Potentiostat/Galvanostat MMate 510, in a three – electrode cell.
The aim of the present work was to determine the electrochemical surface area of the CNFs – Pt catalysts, using an electrochemical method. The obtained results correlate very well with the particles size and distribution of platinum, analyzed by SEM (scanning electron microscopy) respectively with the quantity of deposited platinum determined by TG (thermo gravimetrical analyses). Cyclic voltammetry is a suitable method for estimation of the real surface area for catalyst particles.
In state of the art polymer electrolyte membrane fuel cells (PEMFC) rare and expensive platinum group metals (PGM) are used as catalyst material. Reduction of PGM in PEMFC electrodes is strongly required to reach cost targets for this technology. An optimal catalyst utilisation is achieved in the case of nano-structured particles supported on carbon material with a large specific surface area. In this study, graphitic material in form of carbon nanofibres (CNFs) is decorated with platinum (Pt) particles serving as catalyst material for PEMFC electrodes with low Pt loading. For electrode preparation CNFs have been previously activated by means of radio frequency induced oxygen plasma. This kind of treatment results in formation of functional groups on the CNF’s surface which directly influences the characteristics of subsequent Pt particle deposition. Different plasma parameters (plasma power, gas flow or exposure time) have to be set in order to achieve formation of oxygen containing functional groups (hydroxylic, carboxylic or carbonylic) on the CNF’s surface. In the frame of this experimental work, electrodes are investigated in respect of optimal morphology, microstructure as well as electrochemical properties. Therefore, samples were characterised by means of scanning electron microscopy combined with energy dispersive X-ray analysis, transmission electron microscopy, thermogravimetry, X-ray diffraction, X-ray fluorescence as well as polarisation measurements.
Steganography, the art of concealing information in different types of medias, is a very old practice. Yet, it only recently started being used by malware operators on a large scale. Malware programmers and operators are increasing their efforts in developing covert communication channels between infected computers and their command and control servers. In addition to steganography, recent examples include hiding communication in inconspicuous network traffic such as DNS queries or HTTP 404 error messages.
When used properly, these covert communication channels can bypass many automated detection mechanisms and render malware communication difficult to detect and block. From an attacker's perspective, covert communication channels are a valuable addition because they allow messages to blend in with legitimate traffic and thus significantly lower the chance of being detected even when inspected by a human analyst.
This presentation studies recent advances in covert communication channels used by real-world malware. First, we will show how steganography has recently been used in three different malware families (Stegoloader, Vawtrak, and Lurk). We will dive into the implementation details on how steganography is implemented and discuss the strengths and weaknesses of each approach. Furthermore, we will detail and compare the usage of inconspicuous carrier protocols for covert communication channels in malware. Examples will span commodity cybercrime as well as targeted attack malware.
The cases that are discussed in this presentation are based on real life incidents. While it is easy to speculate how covert communication channels might be used by malicious actors, documentation of real-world cases is sparse. Yet covert communication channels have arrived in both, the commodity cybercrime and targeted attack world. It is thus vital to understand the status-quo and identify current trends in cybercriminal and targeted attack malware. As such, we believe that it is mandatory to highlight what is currently being used in the wild.