Nanostructured Electrolytic Composites Based on Cobalt Alloys …
735
The chemical composition of the coatings was determined by energy-dispersive
X-ray spectroscopy by an Oxford INCA Energy 350 electron probe microanalysis
integrated into the system of the SEM. The X-rays were excited by exposure of the
samples to a beam of 15 keV electrons. The surface morphology of the deposits was
studied with a Zeiss EVO 40XVP scanning electron microscope (SEM). Images were
made registering secondary electrons (SEs) via scanning with an electron beam; this
mode made it possible to study topography with a high resolution and contrast ratio.
The surface relief and morphology were evaluated by the contact method on 10 ×
10 × 2 mm samples with an NT-206 scanning probe AFM microscope (lateral and
vertical resolutions 2 and 0.2 nm, respectively; 1024 × 1024 scanning matrix, CSC
cantilever B as a probe, probe tip radius being 10 nm) [22–24].
The structure of the coatings deposited onto the copper substrate was examined
by X-ray diffraction analysis using a diffractometer (DRON-3.0) in the emission of
cobalt anode and CuKα radiation. The compounds (phases) were identified by the
method of comparison of interplane distances (d, A), and relative intensities (I/I 0 )
of the experimental curve with electron PCPDFWIN card index data.
The polarization dependences were obtained for Co–Mo–W(Zr) electrodes using
the potentiostat PI-501.1, and the programmer PR-8 equipped with the special device
intended for the digital data registration. Cyclic voltammetry data (CVA) were
analyzed at the potential scanning rate of s = 0.002–0.05 V/s according to the algorithm given in [25]. The standard three-electrode cell was used for the measurements,
the platinum spiral served as an auxiliary electrode, and the reference electrode was
the saturated silver chloride connected to the cell via the salt bridge. The electrolytes
of 0.25 M NaOH and 0.25 M NaOH + 1 M CH 3 OH compositions were prepared
using purely for analysis reagents and distilled water.
The coating corrosion resistance was studied using the method of electrode
impedance in the model solution of 0.25 M NaOH. The electrochemical impedance
spectra (EIS) of the electrodes with the coatings that have a working area of 1 cm
2
arranged at a distance of 1 cm from each other in the two-electrode cell were registered
in the frequency range of 10
−2 –10
6 Hz at the free corrosion potential using the electrochemical module Autolab-30 (type PGSTAT301N Metrohm Autolab) equipped
with the frequency response analyzer module (type FRA-2). The measurements were
performed at 18 ± 1 °C. The module was controlled using the Autolab 4.9 program
according to the standard procedure with the subsequent processing by the Zview 2.0
package. The phase interface structure was simulated using the method of equivalent
circuits. The EIS results are discussed according to known approaches [26, 27].
2 Theoretical Preconditions
A complete methanol oxidation is a multistage process that can be represented as a
series of stages:
(CH 3 OH) L → (CH 3 OH) S → (HCHO) S → (HCOO
−
) S → (CO) S → CO 2 , (1)
735
The chemical composition of the coatings was determined by energy-dispersive
X-ray spectroscopy by an Oxford INCA Energy 350 electron probe microanalysis
integrated into the system of the SEM. The X-rays were excited by exposure of the
samples to a beam of 15 keV electrons. The surface morphology of the deposits was
studied with a Zeiss EVO 40XVP scanning electron microscope (SEM). Images were
made registering secondary electrons (SEs) via scanning with an electron beam; this
mode made it possible to study topography with a high resolution and contrast ratio.
The surface relief and morphology were evaluated by the contact method on 10 ×
10 × 2 mm samples with an NT-206 scanning probe AFM microscope (lateral and
vertical resolutions 2 and 0.2 nm, respectively; 1024 × 1024 scanning matrix, CSC
cantilever B as a probe, probe tip radius being 10 nm) [22–24].
The structure of the coatings deposited onto the copper substrate was examined
by X-ray diffraction analysis using a diffractometer (DRON-3.0) in the emission of
cobalt anode and CuKα radiation. The compounds (phases) were identified by the
method of comparison of interplane distances (d, A), and relative intensities (I/I 0 )
of the experimental curve with electron PCPDFWIN card index data.
The polarization dependences were obtained for Co–Mo–W(Zr) electrodes using
the potentiostat PI-501.1, and the programmer PR-8 equipped with the special device
intended for the digital data registration. Cyclic voltammetry data (CVA) were
analyzed at the potential scanning rate of s = 0.002–0.05 V/s according to the algorithm given in [25]. The standard three-electrode cell was used for the measurements,
the platinum spiral served as an auxiliary electrode, and the reference electrode was
the saturated silver chloride connected to the cell via the salt bridge. The electrolytes
of 0.25 M NaOH and 0.25 M NaOH + 1 M CH 3 OH compositions were prepared
using purely for analysis reagents and distilled water.
The coating corrosion resistance was studied using the method of electrode
impedance in the model solution of 0.25 M NaOH. The electrochemical impedance
spectra (EIS) of the electrodes with the coatings that have a working area of 1 cm
2
arranged at a distance of 1 cm from each other in the two-electrode cell were registered
in the frequency range of 10
−2 –10
6 Hz at the free corrosion potential using the electrochemical module Autolab-30 (type PGSTAT301N Metrohm Autolab) equipped
with the frequency response analyzer module (type FRA-2). The measurements were
performed at 18 ± 1 °C. The module was controlled using the Autolab 4.9 program
according to the standard procedure with the subsequent processing by the Zview 2.0
package. The phase interface structure was simulated using the method of equivalent
circuits. The EIS results are discussed according to known approaches [26, 27].
2 Theoretical Preconditions
A complete methanol oxidation is a multistage process that can be represented as a
series of stages:
(CH 3 OH) L → (CH 3 OH) S → (HCHO) S → (HCOO
−
) S → (CO) S → CO 2 , (1)