Preparation of Anodes for Methanol Oxidation by
Spontaneous Deposition of Pd onto Porous Ni or Co
Enrico Verlato, Sandro Cattarin, Nicola Comisso,
Marco Musiani, Lourdes Vázquez-Gómez
IENI CNR, Corso Stati Uniti 4, 35127 Padova, Italy
[email protected]
Anodes for the oxidation of methanol in basic media were prepared by a two-step
procedure involving: (i) the electrodeposition of porous Ni [1] (or Co) layers and then
(ii) the spontaneous deposition of Pd by immersion of these layers in acid PdCl 2
solutions. Pd deposition is testified by the appearance of a cathodic peak at ca. -0.29
V, due to PdO reduction, in the cyclic voltammograms recorded in 1 M KOH. The size
of this peak increases with the immersion time in the PdCl2 solution; the peak current
density measured after a 3-hour immersion is ca. 40 times higher than that measured
with a polished Pd electrode. The size of the peaks due to the NiO/NiOOH redox
system, centred at ca. 0.45 V, also increases with the immersion time, because Ni
corrosion promoted by Pd2+ tends to further increase the porous Ni surface area and Ni
does not become entirely coated by Pd.
A CV curve recorded in 1 M KOH + 0.5 M CH3OH shows that the Pd-modified porous
Ni electrode is very active in methanol oxidation. The peak current density, ca. 235 mA
cm-2, is almost 500 times higher than that measured on polished Pd and about twice
higher than that measured with electrodes based on ultrafine nanoporous Pd particles
[2]. Comparable performance is obtained by depositing Pd onto porous Co layers.
J in 1M KOH / A cm
-2
d
c
0.01
b
a
0.00
a: Porous Ni in 1M KOH
b: Pd Modified Porous Ni in 1M KOH
c: Pd Modified Porous Ni in 1M KOH
d: Pd Modified Porous Ni in 1M KOH
+ 0.5M CH 3OH
-0.01
-0.02
0.2
0.0
-0.2
-0.4
-0.03
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
J in 1M KOH + 0.5M CH3OH / A cm
-2
0.02
Cyclic voltammograms
recorded with porous
Ni (a) and Pd-modified
porous Ni electrodes (bd) in 1 M KOH (a-c) or
1 M KOH + 0.5 M
CH3OH (d). Immersion
time of porous Ni in
PdCl2 solution: 30 min
(b) or 3 hours (c, d).
Sweep rate: 10 mV s-1.
E vs Hg/HgO / V
Acknowledgment: The authors acknowledge the financial support of the Italian
Ministry for Economic Development (MSE) – MSE-CNR Agreement on National
Electrical System.
[1] C.A. Marozzi, A.C. Chialvo, Electrochim. Acta 45 (2000) 2111.
[2] X. Wang, W. Wang, Z. Qi, C. Zhao, H. Ji, Z. Zhang, Electrochem. Comm. 11
(2009) 1896.