Co-Magneli phases electrocatalysts for hydrogen/oxygen evolution

Abstract

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

Electrochemical study of Ir–Sn–Sb–O materials as catalyst-supports for the oxygen evolution reaction

“…For instance, the high operational potentials limit the use of carbon based support materials in SPEWEs, the most common material support used in fuel cells, because degradation and loss of electrical contact with the electroactive material is typically observed. Therefore, the catalyst support materials should possess several important features: (i) a highly superficial surface to allow for good dispersion of the catalyst nanoparticles, (ii) a high electrical conductivity to allow for efficient transport of electrons to the ions involved in the electrochemical reactions, (iii) mechanical and chemical stability, and (iv) a good metal support interaction to improve the intrinsic catalytic activity of the catalyst phase [13,14]. The support materials that have been studied for OER are based on oxides and other ceramics, which include Ti n O 2n-1 [14], TiC, SiC-Si, SnO 2 [15,16] and Sb-SnO 2 [5].…”

“…Therefore, the catalyst support materials should possess several important features: (i) a highly superficial surface to allow for good dispersion of the catalyst nanoparticles, (ii) a high electrical conductivity to allow for efficient transport of electrons to the ions involved in the electrochemical reactions, (iii) mechanical and chemical stability, and (iv) a good metal support interaction to improve the intrinsic catalytic activity of the catalyst phase [13,14]. The support materials that have been studied for OER are based on oxides and other ceramics, which include Ti n O 2n-1 [14], TiC, SiC-Si, SnO 2 [15,16] and Sb-SnO 2 [5]. Although these materials have exhibited good properties as catalyst support, new material and/or modification of existing methods for the synthesis of supports are still desired to enhance the electrocatalytic properties and stability of the active materials for the OER.…”

Oxygen evolution on Ebonex-supported Pt-based binary compounds in PEM water electrolysis

“…The stable behavior and good corrosion resistance at the high anodic potentials of Ebonex has been already demonstrated during oxygen evolution, where Magneli phases serve not only as a supporting material, but also contribute to the efficiency of the composite catalyst [31]. For the compositions studed herein, the XPS analysis showed a realization of electronic hypo-hyper-d-metal-support interactions and Pt-M alloying leading to changes in the electronic density of the atoms and the surface-intermediate bond strength as well.…”

Oxygen‐Deficient Ti0.9Nb0.1O2‐x as an Efficient Anodic Catalyst Support for PEM Water Electrolyzer

“…[24] For the IrO 2 /TNO−Hx (x=600, 750, 900) samples, all the shapes of these voltammograms are similar with that of IrO 2 /TiO 2 and IrO 2 /TNO except an additional peak appear at approximately 0.7 V vs . RHE, which could be associated with the voltammetric response of the introduced oxygen vacancies . The unsupported IrO 2 shows the lowest voltammetric charges, and IrO 2 /TiO 2 exhibits higher voltammetric charges than unsupported IrO 2 , which could be the efficient dispersion of IrO 2 supported on TiO 2 .…”