The characterisation of PbO2–coated electrodes prepared from aqueous methanesulfonic acid under controlled deposition conditions

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Description/Abstract

A series of PbO2 electrodes on planar carbon substrates has been prepared by anodic
4 deposition in aqueous methanesulfonic acid (MSA) under galvanostatic conditions. The effect
5 of four experimental parameters, i.e., lead(II) methanesulfonate and MSA concentrations,
6 current density and temperature was analysed. Surface characterisation by XRD, SEM-EDX
7 and AFM has provided information about the structural (phase distribution, degree of
8 crystallinity and crystallite size), morphological (crystallite shape, degree of porosity) and
9 tribological (surface roughness) properties of the PbO2 coatings, respectively.
10 Electrochemical studies based on linear and cyclic voltammetry allowed comparison between
11 electrodes prepared in MSA and classical electrodes prepared in HNO3. Pure - or -PbO2
12 and  +  mixtures were obtained depending on the conditions, being temperature the most
13 influential deposition parameter. A temperature rise caused a transition to pure -PbO2 and
14 led to a higher degree of crystallinity with a progressive increase of crystallite size, always
15 within the range of 10-30 nm, as well as to a remarkably higher roughness, from smooth (35-
16 50 nm rms) to rough (up to 500 nm rms) surfaces. Low MSA and high lead(II)
17 methanesulfonate concentrations were required to avoid the formation of excessively porous
18 powdery coatings, as well as cracks, pits and holes. Most of the coatings obtained in MSA
19 were uniform, nanocrystalline and moderately rough. Their electrocatalytic behaviour was
20 comparable to that of the electrodes prepared in HNO3, showing an O2-overpotential of + 0.66
21 V in 0.05 M Na2SO4 at pH 3.0. Such coatings can then be envisaged as suitable anodes for
22 energy and water treatment applications. Prolonged electrolysis has shown their stability
23 against leaching