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Ebonex CoHydrogen evolution Oxygen evolution a b s t r a c tThe subject of this work is the use of non-stoichiometric titanium oxides e Magneli phases as support material of Co-based electrocatalysts aimed for hydrogen/oxygen evolution reaction. Commercial micro-scaled Ebonex (Altraverda, UK) was mechanically treated for 4, 8, 12, 16 and 20 h and further Co metallic phase was grafted by sol-gel method.Morphology of Co/Ebonex electrocatalysts was observed by means of TEM and SEM microscopy, while electrochemical behavior by means of cyclic voltammetry and steadystate galvanostatic method.As the duration of mechanical treatment increases, the size of Magneli phases decreases, and consequently catalytic activity of the corresponding electrocatalysts increases.Structural characteristics of the electrocatalysts deposited on Ebonex treated for 16 and 20 h are very similar. Also, these electrocatalysts show similar electrocatalytic activity for both hydrogen and oxygen evolution reaction. So, optimal duration of mechanical treatment of Magneli phases is in the range of 16e20 h.Catalytic activity for hydrogen evolution of the studied electrocatalysts is inferior related to the corresponding catalysts deposited on carbonaceous support materials such as activated multiwalled carbon nanotubes or Vulcan XC-72 þ TiO 2 (anatase). This inferiority is due to lower real surface area of the Magneli phases.Catalytic behavior for oxygen evolution achieves its maximal value even at the catalyst deposited on Ebonex treated for 12 h and it is very promising related to the similar electrocatalytic system such as CoPt/Ebonex. ª 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved. IntroductionRecent intensive development of hydrogen economy as an alternative energy system in the future imposes invention and research on new effective electrode materials. The modern electrode materials are composed of nanostructured catalytic phase dispersed over the support material that has to possess several very important characteristics, such as: i) highly developed surface area to provide better dispersion of the nano-scaled catalytic particles; ii) high electric conductivity to allow efficient electron transfer to ions involved in the electrochemical reactions, iii) mechanical and chemical stability and iv) to improve intrinsic catalytic activity of the active catalytic phase through the strong metalesupport interaction (SMSI) [1,2]. Carbon nanostructured materials such as carbon blacks are commercially the most used support material [3,4], * Corresponding author. Tel./fax: þ389 2 3064 392. E-mail address: pericap@tmf.ukim.edu.mk (P. Paunovi c).A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / h e i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 5 ( 2 0 1 0 ) 1 0 0 7 3 e1 0 0 8 0

<p class="Adressess">The preparation of a large number of materials trough the propagating exothermic reactions has been the objective of numerous investigation. Self-propagating reactions are typically associated with high temperatures and extremely steep thermal gradients and thus offer the opportunity to investigate the formation of intermediate and metastable phases. Such reactions are also of interest from a practical point of view since, as has been described in numerous literature accounts, they provide the opportunity to prepare materials with unique properties.</p><p class="Adressess">In this study the thermal effects of dissolution on the solid nickel in liquid aluminum and formation intermetallic phases was studied by simple experimental procedure. The thermal effects generated by exothermic solid-liquid metal interaction was judged by the rise of temperature in the system. Depending on experimental conditions, two different regimes of behavior were found: solid-liquid interaction leading to the considerable rise of the temperature in the system, and characterized by continuos decrease of the temperature in the system with time. The results of the experiments on the heat effects during the interaction of solid nickel with different particle size and liquid aluminum, with and without external mixing, are presented. It has been shown that, depending on experimental conditions, the evolved heat may influence the structure of a zone near to the solid-liquid interface. The experimental procedure correlates with the practical conditions of semi-industrial production of aluminum-nickel master alloys with relatively high percentage of nickel.</p>

This study is concerned with preparation and characterization of Co-Ru based hypo-hyper d-electrocatalysts aimed for water electrolysis. The composition of the studied electrocatalysts was: 10 % mixed metallic phase (Co : Ru = 1 : 1 wt., Co:Ru = 4 : 1 wt. and Co : Ru : Pt = 4 : 0.5 : 0.5), 18 % TiO2 as a crystalline anatase deposited on activated multiwalled carbon nanotubes (MWCNTs). For comparison, corresponding electrocatalysts with pure hyper d-metallic phase (Co and Ru) were prepared. The structural characterization of the studied electrocatalysts was performed by means of XRD, SEM and FTIR analysis. The prepared hypo-hyper d-electrocatalysts were electrochemically studied by cyclic voltammetry and potentiodynamic method in the alkaline hydrogen electrolyser. The order of the catalytic activity for hydrogen evolution of studied electrocatalysts was the following: Ru > CoRuPt (4 : 0.5 : 0.5, wt.) > CoRu (1 : 1 wt.) > CoRu (4 : 1 wt.) > Co. The electrocatalyst with only 20 % precious metals (Pt and Ru) in the metallic phase (the rest being Co-metal) exhibited excellent performance approaching that of the electrocatalyst with 100 % precious metallic phase (Ru).