38 research outputs found
Preparation and characterization of CoeRu/TiO2/MWCNTs electrocatalysts in PEM hydrogen electrolyzer
The subject of this study is preparation and characterization of hypoehyper d-electrocatalysts
with reduced amount of precious metals aimed for water electrolysis. The studied electrocatalysts contain 10% mixed metallic phase (Co:Ru ΒΌ 1:1 wt., Co:Ru ΒΌ 4:1 wt. and
Co:Ru:Pt ΒΌ 4:0.5:0.5 wt.), 18% TiO2 as a crystalline anatase deposited on multiwalled carbon nanotubes (MWCNTs). Previously, MWCNTs were activated in 28% nitric acid. As a reference electrocatalyst for hydrogen evolution reaction, corresponding electrocatalysts with pure Pt metallic phase and mixed CoPt (Co:Pt ΒΌ 1:1 wt.) metallic phase were prepared. Also, as a reference electrocatalyst for oxygen evolution reaction, electrocatalyst with pure Ru
metallic phase was prepared.
The prepared electrocatalysts were structurally characterized by means of XPS, XRD,TEM, SEM and FTIR analysis.
Electrochemical characterization was performed by means of cyclic voltammetry and potentiodynamic method in the PEM hydrogen electrolyzer. The range of the catalytic
activity for hydrogen evolution of studied electrocatalysts was the following: CoRuPt (4:0.5:0.5) > CoPt (1:1) > Pt > CoRu (1:1) > CoRu (4:1). The order of the catalytic activity for oxygen evolution was the following: CoRu (1:1) > Ru > CoRu (4:1) > Pt > CoRuPt (4:0.5:0.5) > CoPt (1:1)
Π’ΠΎΠΊΡΠΈΡΠ½ΠΈ Π΅Π»Π΅ΠΌΠ΅Π½ΡΠΈ Π²ΠΎ ΠΎΡΠΈΠ·, ΠΏΡΠ΅Π½ΠΈΡΠ½ΠΎ Π±ΡΠ°ΡΠ½ΠΎ ΠΈ ΠΏΡΠΎΠΈΠ·Π²ΠΎΠ΄ΠΈ ΠΎΠ΄ Π±ΡΠ°ΡΠ½ΠΎ ΠΎΠ΄ ΠΌΠ°ΠΊΠ΅Π΄ΠΎΠ½ΡΠΊΠΈΠΎΡ ΠΏΠ°Π·Π°Ρ
The safety of the cereal products is of high nutritional and toxicological interest, since the cereal industry and its products have a big economic and social importance worldwide. In this pilot research the presence and the content of toxic trace elements arsenic, cadmium and lead in three samples of rice: 11,67+5,69mg/kg, 25,67+6,43mg/kg, 47,67+18,01mg/kg for As, Cd and Pb respectively, wheat flour: 7+5mg/kg, 9+1,73mg/kg, 69,92+16,92mg/kg and flour products (bread: 9,33+2,08mg/kg, 6,67+0,58mg/kg, 36+3,6mg/kg, pasta: 1,61+1,15mg/kg, 2,67+2,08mg/kg, 30+7mg/kg and tea biscuits: 4,67+4,04mg/kg, 1,33+0,58mg/kg, 53+9,64mg/kg for As, Cd and Pb respectively) produced by three different manufacturers from Macedonia was determined by applying the hydride generation and electrothermal atomic absorption spectrometry with wet digestion. In this research the contribution to the average daily intake for toxic elements through daily intake of cereal and cereal products (20% of the all-day meal) has been determined. The contribution of As (9,86%), Cd (10,02%) and Pb (11,39%) compared to the average daily intake and the PTDI was low, which indicates that these products are safe for consumption concerning the examined toxic elements. The levels of the toxic elements in the samples of Macedonian rice, wheat flour, bread, pasta and tea biscuits are comparable to those obtained from various parts of the world and their consumption does not pose any health risks.ΠΠ΅Π·Π±Π΅Π΄Π½ΠΎΡΡΠ° Π½Π° ΠΆΠΈΡΠ°ΡΠ° ΠΈ ΠΆΠΈΡΠ½ΠΈΡΠ΅ ΠΏΡΠΎΠΈΠ·Π²ΠΎΠ΄ΠΈ Π΅ ΠΎΠ΄ Π³ΠΎΠ»Π΅ΠΌΠΎ Π½ΡΡΡΠΈΡΠΈΠ²Π½ΠΎ ΠΈ ΡΠΎΠΊΡΠΈΠΊΠΎΠ»ΠΎΡΠΊΠΎ Π·Π½Π°ΡΠ΅ΡΠ΅, Π±ΠΈΠ΄Π΅ΡΡΠΈ ΠΆΠΈΡΠ½Π°ΡΠ° ΠΈΠ½Π΄ΡΡΡΡΠΈΡΠ° ΠΈ Π½Π΅ΡΠ·ΠΈΠ½ΠΈΡΠ΅ ΠΏΡΠΎΠΈΠ·Π²ΠΎΠ΄ΠΈ ΠΈΠΌΠ°Π°Ρ Π³ΠΎΠ»Π΅ΠΌΠ° Π΅ΠΊΠΎΠ½ΠΎΠΌΡΠΊΠ° ΠΈ ΡΠΎΡΠΈΡΠ°Π»Π½Π° Π²Π°ΠΆΠ½ΠΎΡΡ Π½Π° ΡΠ²Π΅ΡΡΠΊΠΎ Π½ΠΈΠ²ΠΎ. ΠΠΎ ΠΎΠ²Π° ΠΏΠΈΠ»ΠΎΡ ΠΈΡΡΡΠ°ΠΆΡΠ²Π°ΡΠ΅ Π΅ ΠΈΡΠΏΠΈΡΠ°Π½Π° ΠΊΠΎΠ½ΡΠ΅Π½ΡΡΠ°ΡΠΈΡΠ°ΡΠ° Π½Π° ΡΠΎΠΊΡΠΈΡΠ½ΠΈΡΠ΅ Π΅Π»Π΅ΠΌΠ΅Π½ΡΠΈ Π²ΠΎ ΡΡΠ°Π³ΠΈ Π°ΡΡΠ΅Π½, ΠΊΠ°Π΄ΠΌΠΈΡΠΌ ΠΈ ΠΎΠ»ΠΎΠ²ΠΎ, Π²ΠΎ ΡΡΠΈ ΠΌΠΎΡΡΡΠΈ ΠΎΠ΄ ΡΠ°Π·Π»ΠΈΡΠ½ΠΈ ΠΏΡΠΎΠΈΠ·Π²ΠΎΠ΄ΠΈΡΠ΅Π»ΠΈ Π½Π° ΠΎΡΠΈΠ·: 11,67+5,69mg/kg, 25,67+6,43mg/kg, 47,67+18,01mg/kg, ΠΏΡΠ΅Π½ΠΈΡΠ½ΠΎ Π±ΡΠ°ΡΠ½ΠΎ: 7+5mg/kg, 9+1,73mg/kg, 69,92+16,92mg/kg Π·Π° As, Cd ΠΈ Pb, ΡΠΎΠΎΠ΄Π²Π΅ΡΠ½ΠΎ, ΠΈ ΠΏΡΠΎΠΈΠ·Π²ΠΎΠ΄ΠΈ ΠΎΠ΄ Π±ΡΠ°ΡΠ½ΠΎ (Π»Π΅Π±: 9,33+2,08mg/kg, 6,67+0,58mg/kg, 36+3,6mg/kg, ΡΠ΅ΡΡΠ΅Π½ΠΈΠ½ΠΈ: 1,61+1,15mg/kg, 2,67+2,08mg/kg, 30+7mg/kg ΠΈ ΡΠ°ΡΠ½ΠΈ ΠΊΠΎΠ»Π°ΡΠΈ: 4,67+4,04mg/kg, 1,33+0,58mg/kg, 53+9,64mg/kg Π·Π° As, Cd ΠΈ Pb, ΡΠΎΠΎΠ΄Π²Π΅ΡΠ½ΠΎ) ΠΎΠ΄ ΠΌΠ°ΠΊΠ΅Π΄ΠΎΠ½ΡΠΊΠΈΠΎΡ ΠΏΠ°Π·Π°Ρ, ΡΠΎ ΡΠΏΠΎΡΡΠ΅Π±Π° Π½Π° Ρ
ΠΈΠ΄ΡΠΈΠ΄Π½ΠΎ Π³Π΅Π½Π΅ΡΠΈΡΠ°ΡΠΊΠ° ΠΈ Π΅Π»Π΅ΠΊΡΡΠΎΡΠ΅ΡΠΌΠΈΡΠΊΠ° Π°ΡΠΎΠΌΡΠΊΠ° Π°ΠΏΡΠΎΡΠΏΡΠΈΠΎΠ½Π° ΡΠΏΠ΅ΠΊΡΡΠΎΠΌΠ΅ΡΡΠΈΡΠ° ΡΠΎ ΠΌΠΎΠΊΡΠ° Π΄ΠΈΠ³Π΅ΡΡΠΈΡΠ°. ΠΠ·Π²ΡΡΠ΅Π½Π° Π΅ ΠΏΡΠ΅ΡΠΌΠ΅ΡΠΊΠ° Π½Π° ΡΡΠ΅ΡΡΠ²ΠΎΡΠΎ Π²ΠΎ ΠΏΡΠΎΡΠ΅ΡΠ½ΠΈΠΎΡ Π΄Π½Π΅Π²Π΅Π½ Π²Π½Π΅Ρ Π·Π° ΡΠΎΠΊΡΠΈΡΠ½ΠΈ Π΅Π»Π΅ΠΌΠ΅Π½ΡΠΈ Π²Π½Π΅ΡΠ΅Π½ΠΈ ΠΏΡΠ΅ΠΊΡ Π΄Π½Π΅Π²Π½Π° ΠΊΠΎΠ½ΡΡΠΌΠ°ΡΠΈΡΠ° Π½Π° ΠΆΠΈΡΠΎ ΠΈ ΠΏΡΠΎΠΈΠ·Π²ΠΎΠ΄ΠΈ ΠΎΠ΄ ΠΆΠΈΡΠΎ (20% ΠΎΠ΄ ΡΠ΅Π»ΠΎΠ΄Π½Π΅Π²Π½ΠΈΠΎΡ ΠΎΠ±ΡΠΎΠΊ). ΠΡΠΈΠ΄ΠΎΠ½Π΅ΡΠΎΡ Π½Π° As (9,86%), Cd (10,02%) ΠΈ Pb (11,39 %) ΡΠΏΠΎΡΠ΅Π΄Π΅Π½ ΡΠΎ ΠΏΡΠΎΡΠ΅ΡΠ½ΠΈΠΎΡ Π΄Π½Π΅Π²Π΅Π½ Π²Π½Π΅Ρ ΠΈ ΠΏΡΠΈΡΠ°ΡΠ»ΠΈΠ²ΠΈΠΎΡ ΡΠΎΠ»Π΅ΡΠΈΡΠ°Π½ Π΄Π½Π΅Π²Π΅Π½ Π²Π½Π΅Ρ, PTDI, Π±Π΅ΡΠ΅ Π½ΠΈΠ·ΠΎΠΊ, ΡΡΠΎ ΠΏΠΎΠΊΠ°ΠΆΡΠ²Π° Π΄Π΅ΠΊΠ° ΠΎΠ²ΠΈΠ΅ ΠΏΡΠΎΠΈΠ·Π²ΠΎΠ΄ΠΈ ΡΠ΅ Π±Π΅Π·Π±Π΅Π΄Π½ΠΈ Π·Π° ΡΠΏΠΎΡΡΠ΅Π±Π° Π²ΠΎ ΠΎΠ΄Π½ΠΎΡ Π½Π° ΠΈΡΠΏΠΈΡΠ°Π½ΠΈΡΠ΅ ΡΠΎΠΊΡΠΈΡΠ½ΠΈ Π΅Π»Π΅ΠΌΠ΅Π½ΡΠΈ. ΠΠΈΠ²ΠΎΠ°ΡΠ° Π½Π° ΡΠΎΠΊΡΠΈΡΠ½ΠΈΡΠ΅ Π΅Π»Π΅ΠΌΠ΅Π½ΡΠΈ Π²ΠΎ ΠΌΠΎΡΡΡΠΈΡΠ΅ Π½Π° ΠΌΠ°ΠΊΠ΅Π΄ΠΎΠ½ΡΠΊΠΈΠΎΡ ΠΎΡΠΈΠ·, ΠΏΡΠ΅Π½ΠΈΡΠ½ΠΎ Π±ΡΠ°ΡΠ½ΠΎ ΠΈ ΠΏΡΠΎΠΈΠ·Π²ΠΎΠ΄ΠΈ ΠΎΠ΄ Π±ΡΠ°ΡΠ½ΠΎ ΡΠ΅ ΡΠΏΠΎΡΠ΅Π΄Π»ΠΈΠ²ΠΈ ΡΠΎ ΡΠ΅Π·ΡΠ»ΡΠ°ΡΠΈΡΠ΅ Π΄ΠΎΠ±ΠΈΠ΅Π½ΠΈ ΠΎΠ΄ ΡΠ°Π·Π»ΠΈΡΠ½ΠΈ Π΄Π΅Π»ΠΎΠ²ΠΈ ΠΎΠ΄ ΡΠ²Π΅ΡΠΎΡ ΠΈ Π½ΠΈΠ²Π½ΠΈΠΎΡ Π²Π½Π΅Ρ Π½Π΅ ΠΏΡΠ΅ΡΡΡΠ°Π²ΡΠ²Π° Π·Π΄ΡΠ°Π²ΡΡΠ²Π΅Π½ ΡΠΈΠ·ΠΈΠΊ Π·Π° ΠΏΠΎΡΡΠΎΡΡΠ²Π°ΡΠΈΡΠ΅
Electrocatalysts in the last 30 years β from precious metals to cheaper but sophisticated complex systems
The paper is concerned with the advance and diversification of materials used as electrodes for evolution of
chlorine, hydrogen and oxygen. In the first part a survey is given of our research in the field of electrocatalysis 30
years ago, when Ru and other precious metals were the exclusive electrocatalyst materials. A brief scope of the
achievements of electrocatalysis in that period is given as well. The second part deals with our recent research on
formulation and characterization of a new class of electrocatalysts, based on a combination of non-precious metals,
but still exhibiting an ability to promote hydrogen evolution reaction as successful as platinum and other precious
metals are.
Among the produced (non-platinum) catalysts the best performance for the hydrogen evolution reaction was
measured at the electrocatalyst containing Co or CoNi as hyper d phase and TiO2 as hypo d phase. A typical formulation
of the electrodes is, e.g.: 18% (TiO2) alloyed with 10% Co and applied on a substrat of carbon powder (Vulcan
XC-72). At this electrocatalyst hydrogen evolution overpotential at 10 mAΒ·cmβ2 was 40 mV higher than that on a
corresponding electrode containing platinum as hyper d phase.
For both electrocatalyst systems of interest analysis is made and aimed to recognize the sources that cause the
electrocatalytic activity. This is the proper way how to use the acquired knowledge for further improvement of the
existing materials or/and to discover new ones.
Key words: electrocatalysis; hydrogen evolution; hypo-hyper d-electrocatalyst
Improvement of performances of complex non-platinum electrode materials for hydrogen evolution
Abstract
Structural and electrochemical characteristics of hypoβhyper d-electrocatalytic materials aimed for preparation of electrodes for hydrogen
evolution were studied and modified in order to improve their performances. All studied materials were of general composition 10% Ni + 18%
TiO2 +C.
All materials were prepared of amorphous or crystalline TiO2, crystalline Ni or NiCo (10β20 nm) and Vulcan XC-72, by solβgel procedure.
Both, materialβs intrinsic catalytic activity and surface area were affected by applied modifications. As a result, the electrocatalytic activity
was improved, e.g. transformation of TiO2 into anatase form lowers the HER overpotential for 60mV. Introduction of MWCNTs was even more
effective, lowering Ξ· for 120mV. Co addition to metallic phase lowers Ξ· for utmost 195mV.
Combined modification of TiO2 and carbon substrate lowers Ξ· for 145mV, while the complete modification of all three catalystβs components
was the most effective with 230mV decrease of overpotential.
Β© 2006 Elsevier Ltd. All rights reserved.
Keywords: Hydrogen evolution; Hypoβhyper d-electrocatalysts; Non-platinum metal
ΠΠ΅ΡΠ΅ΠΊΡΠΈΡΠ° ΠΈ Π°Π½Π°Π»ΠΈΠ·Π° Π½Π° ΡΡΠΎΠΏΠ°Π½ΡΠΊΠΈΡΠ΅ Π΅ΠΊΡΠΏΠ»ΠΎΠ·ΠΈΠ²ΠΈ ΠΏΠΎ Π½ΠΈΠ²Π½ΠΎΡΠΎ Π°ΠΊΡΠΈΠ²ΠΈΡΠ°ΡΠ΅ - Π΅ΠΊΡΠΏΠ»ΠΎΠ·ΠΈΡΠ°
ΠΠΎ ΡΡΡΠ΄ΠΎΡ ΡΠ΅ Π²ΡΡΠ΅Π½ΠΈ ΠΈΡΠΏΠΈΡΡΠ²Π°ΡΠ°, ΠΎΠ΄Π½ΠΎΡΠ½ΠΎ Π΄Π΅ΡΠ΅ΠΊΡΠΈΡΠ° Π½Π° ΡΡΠΎΠΏΠ°Π½ΡΠΊΠΈΡΠ΅ Π΅ΠΊΡΠΏΠ»ΠΎΠ·ΠΈΠ²ΠΈ ΠΏΠΎΡΠ»Π΅ Π½ΠΈΠ²Π½Π°ΡΠ° Π΅ΠΊΡΠΏΠ»ΠΎΠ·ΠΈΡΠ°. ΠΠ° ΡΠ°Π° ΡΠ΅Π» ΠΈΠ·Π²ΡΡΠ΅Π½ΠΎ Π΅ Π°ΠΊΡΠΈΠ²ΠΈΡΠ°ΡΠ΅ Π½Π° 1 ΠΊΠ³ ΡΡΠΎΠΏΠ°Π½ΡΠΊΠΈ Π΅ΠΊΡΠΏΠ»ΠΎΠ·ΠΈΠ² Π°ΠΌΠΎΠ½Π΅ΠΊΡ. ΠΠΊΡΠΈΠ²ΠΈΡΠ°ΡΠ΅ΡΠΎ Π΅ ΠΈΠ·Π²ΡΡΠ΅Π½ΠΎ ΡΠΎ ΡΡΠ°Π½Π΄Π°ΡΠ΄Π½ΠΎ ΡΡΠ΅Π΄ΡΡΠ²ΠΎ Π·Π° ΠΈΠ½ΠΈΡΠΈΡΠ°ΡΠ΅. ΠΠΎ Π΅ΠΊΡΠΏΠ»ΠΎΠ°ΡΠ°ΡΠΈΡΠ°ΡΠ°, Π½Π° ΡΠ°Π·Π½ΠΈ ΡΠ°ΡΡΠΎΡΠ°Π½ΠΈΡΠ°, Π΅ Π·Π΅ΠΌΠ΅Π½ Π±ΡΠΈΡ. ΠΠΎ Π΄Π²Π΅ΡΠ΅ ΠΏΡΠΎΠ±ΠΈ ΡΠΎ ΠΏΠΎΠΌΠΎΡ Π½Π° ΠΌΠ΅ΡΠΎΠ΄ΠΎΡ Π½Π° ΡΠ΅ΡΠ½Π° Ρ
ΡΠΎΠΌΠ°ΡΠΎΠ³ΡΠ°ΡΠΈΡΠ° ΡΠ΅Π³ΠΈΡΡΡΠΈΡΠ°Π½ΠΎ Π΅ ΠΏΡΠΈΡΡΡΡΠ²ΠΎ Π½Π° Π°ΠΌΠΎΠ½ΠΈΡΠΌ Π½ΠΈΡΡΠ°Ρ, ΡΡΠΈΠ½ΠΈΡΡΠΎΡΠΎΠ»ΡΠ΅Π½ ΠΈ Ρ
Π΅ΠΊΡΠΎΠ³Π΅Π½
Modifications for the improvement of catalyst materials for hydrogen evolution
Abstract: The structural and electrocatalytic characteristics of composite materials
based on non-precious metals were studied. Precursors of metallic phase (Ni, Co or
CoNi) and oxide phase (TiO2) were grafted on a carbon substrate (Vulcan XC-72) by
the solβgel procedure and thermally treated at 250 ΒΊC. Ni and CoNi crystals of 10β20
nm were produced, in contrast the Co and TiO2 were amorphous. The dissimilar
electronic character of the components gives rise to a significant electrocatalytic activity
for the hydrogen evolution reaction (HER), even in the basic series of prepared
materials. Further improvement of the catalysts was achieved by modification of all
three components. Hence, Mo was added into the metallic phase, TiO2 was converted
into the crystalline form and multiwall carbon nanotubes (MWCNTs) were
used instead of carbon particles. The improvement, expressed in terms of the lowering
the hydrogen evolution overpotential at 60 mA cm-2, was the most pronounced
in the Ni-based systems grafted on MWCNTs (120 mV lower HER overpotential)
compared to 60 mV in case of Ni-based systems grafted on crystalline TiO2 (TiO2
prepared at 450 ΒΊC) and of Ni-based systems containing 25 at.% Mo. Nevertheless,
even with the realized enhancement, of all the tested materials, the Co-based systems
remained superior HER catalysts.
Keywords: composite electrocatalysts, hydrogen evolution, electronic interaction,
real surface area
Study of structural and electrochemical characteristics of Co-based hypoβhyper d-electrocatalysts for hydrogen evolution
Abstract
Structural and electrochemical characteristics of hypoβhyper d-electrocatalytic materials aimed for preparation of electrodes for hydrogen
evolution were studied. The basic catalytic material was prepared of 10% amorphous Co (grain size <2 nm), 18% amorphous TiO2 and Vulcan
XC-72, by solβgel procedure. A number of modifications were applied aimed at improving the materials performances: (i) TiO2 was transformed
into anatase by heating at 480 β¦C for 1 h, (ii) multiwalled carbon nanotubes (MWCNT) were used as a catalyst support instead of Vulcan XC-72
and (iii) Mo was added to Co phase in a quantity of 25 at.% (Mo:Co = 1:3).
Both, materialβs intrinsic catalytic activity and surface area were affected by these modifications. As a result, the electrocatalytic activity for
hydrogen evolution was improved, e.g. transformation of TiO2 into anatase form lowers the HER overpotential (Ξ·) for 15mV at 60mAcmβ2.
Introduction of MWCNTs lowered Ξ· for 30mV, while addition of Mo to metallic phase for 40mV.
The complete modification of all three catalystβs components (10% MoCo3 + 18% anatase + MWCNTs) was the most effective with 60mV
decrease of overpotential.
Characterization was made by XRD, SEM, IR and XPS methods. Surface area was measured by means of cyclic voltammetry.
Β© 2007 Elsevier Ltd. All rights reserved.
Keywords: Hydrogen evolution; Hypoβhyper d-electrocatalysis; Co-based electrocatalyst
ΠΠ·Π±ΠΎΡ Π½Π° ΡΠ°ΡΡΠ²ΠΎΡΡΠ²Π°Ρ Π·Π° ΠΈΠ΄Π΅Π½ΡΠΈΡΠΈΠΊΠ°ΡΠΈΡΠ° Π½Π° Π±ΡΠΈΠ·Π°Π½ΡΠ½ΠΈΡΠ΅ Π΅ΠΊΡΠΏΠ»ΠΎΠ·ΠΈΠ²Π½ΠΈ ΠΌΠ°ΡΠ΅ΡΠΈΠΈ
ΠΡΡΠ΅Π½ΠΈ ΡΠ΅ ΠΈΡΠΏΠΈΡΡΠ²Π°ΡΠ°, ΠΎΠ΄Π½ΠΎΡΠ½ΠΎ ΠΈΠ΄Π΅Π½ΡΠΈΡΠΈΠΊΠ°ΡΠΈΡΠ° Π½Π° Π±ΡΠΈΠ·Π°Π½ΡΠ½ΠΈ Π΅ΠΊΡΠΏΠ»ΠΎΠ·ΠΈΠ²Π½ΠΈ ΠΌΠ°ΡΠ΅ΡΠΈΠΈ ΠΊΠΎΠΈ ΡΠ΅ ΡΠΏΠΎΡΡΠ΅Π±ΡΠ²Π°Π°Ρ Π·Π° ΠΌΠΈΠ½ΠΈΡΠ°ΡΠ΅ Π²ΠΎ ΡΡΠ΄Π°ΡΡΡΠ²ΠΎΡΠΎ. ΠΠ° ΡΠ°Π° ΡΠ΅Π» ΠΈΠ·Π²ΡΡΠ΅Π½ΠΎ Π΅ Π°ΠΊΡΠΈΠ²ΠΈΡΠ°ΡΠ΅ Π½Π° 1 ΠΊΠ³. Π±ΡΠΈΠ·Π°Π½ΡΠ΅Π½ Π΅ΠΊΡΠΏΠ»ΠΎΠ·ΠΈΠ², ΠΏΠΎΠ·Π½Π°Ρ ΠΏΠΎΠ΄ ΠΈΠΌΠ΅ΡΠΎ Π°ΠΌΠΎΠ½Π΅ΠΊΡ. ΠΠΊΡΠΈΠ²ΠΈΡΠ°ΡΠ΅ΡΠΎ Π΅ ΠΈΠ·Π²ΡΡΠ΅Π½ΠΎ ΡΠΎ ΡΡΠ°Π½Π΄Π°ΡΠ΄Π½ΠΎ ΡΡΠ΅Π΄ΡΡΠ²ΠΎ Π·Π° ΠΈΠ½ΠΈΡΠΈΡΠ°ΡΠ΅..
Co-Magneli phases electrocatalysts for hydrogen/oxygen evolution
The 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 ΓΎ TiO2 (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
Effect of activation/purification of multiwalled carbon nanotubes (MWCNTs)on the activity of non-platinum based hypo-hyper d-electrocatalysts for hydrogen evolution
Commercial multiwalled carbon nanotubes (MWCNTs) were used as a catalyst support for non-platinum
hypo-hyper d-electrocatalysts. In order to improve the performance of these catalysts, activation/
purification of MWCNTs in acid medium (HNO3) was carried out. The physical and surface changes of
MWCNTs were investigated by DTA/TGA analysis, Raman spectroscopy, and cyclic voltammetry.
Structural changes of the electrocatalysts were observed by infrared spectroscopy and SEM. Their use as
a support for electrocatalysts for hydrogen evolution was demonstrated, and shown to be more suitable
compared to the traditional carbon support material οΏ½ carbon black (Vulcan XC-72). The electrocatalysts consisted of 10% Co + 18% TiO2 + MWCNTs. Activation/purification removes the amorphous carbon phase in theMWCNTs. As a result of both shortening and opening of carbon nanotubes, better dispersion of metallic particles (the active catalytic centers) was achieved. Thus, trans-particle and inter-particle porosity of the electrocatalytic material was improved, implying increase of catalytic activity for
hydrogen evolution