Methanol electrooxidation at nickel-modified rhodanine self assembled monolayer films: A new class of multilayer electrocatalyst

Nickel modified rhodanine (Rh) self-assembled monolayer films (Rh-SAM/Ni) were fabricated on copper from 10.0 mM Rh containing methanol. The films were characterized with the help of scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDX) techniques. The methanol oxidation activity of the Rh-SAM/Ni electrode was tested in 1.0 M methanol containing 0.1 M KOH solution using many electrochemical techniques. The results indicated that well-ordered and very homogeneously distributed Rh-SAM films were assembled over the copper surface. The rate of methanol electrooxidation reaction can be enhanced by modifying copper surface with Rh-SAM/Ni multi-layer film. The enhanced activity was related to increasing active sites over the surface for adsorption and oxidation of methanol as well as facilitating oxidation or desorption of adsorpted intermediates of the process. It was suggested that the Rh-SAM layer could be a candidate supporting material for fabricating direct methanol fuel cell (DMFCs) anodes.     

Oxidation of methanol on perovskite-type La2-xSrxNiO4 (0 ≤ x ≤ 1) film electrodes modified by dispersed nickel in 1 M KOH

Finely-dispersed nickel particles are electrodeposited on high surface-area perovskite-type La_2-xSr_xNiO₄ (0 ≤ x ≤ 1) electrodes for possible use in a direct methanol fuel cell (DMFC). The study is conducted by cyclic voltammetry, chronoamperometry, impedance spectroscopy and anodic Tafel polarization techniques. The results show that the apparent electrocatalytic activities of the modified oxide electrodes are much higher than those of unmodified electrodes under similar experimental conditions; the observed activity is the greatest with the modified La_1.5Sr_0.5NiO₄ electrode. At 0.550 V (vs. Hg|HgO) in 1 M KOH + 1 M CH₃OH at 25 °C, the latter electrode delivers a current density of over 200 mA cm⁻², whereas other electrodes of the series produce relatively low values (65–117 mA cm⁻²). To our knowledge, such high methanol oxidation current densities have not been reported on any other non-platinum electrode in alkaline solution. Further, the modified electrodes are not poisoned by methanol oxidation intermediates/products.     

Influence of the nature of conductive support on the electrocatalytic activity of electrodeposited Ni films towards methanol oxidation in 1 M KOH

The study of electrochemical behaviour of dispersed Ni on graphite, glassy carbon, and Ti electrodes, obtained by an electro-deposition method, is carried out in 1 M KOH + 1 M CH₃OH at 25 °C. Results show that the nature of substrate influences the apparent electrocatalytic activities of the Ni over layer greatly. It is observed that at E = 0.50 V vs. Hg/HgO (25 °C), the dispersed Ni on graphite is approx. 300 times more active than that dispersed on Ti and is approx. 260 times more active than that dispersed on glassy carbon. Further, these electrodes show quite good resistance against electrode poisoning by the methanol oxidation intermediates/products.     

Electrocatalytic oxidation of methanol on mono and bimetallic composite films: Pt and Pt–M (M = Ru,Ir and Sn) nano-particles in poly(o-aminophenol)

Mono and bimetallic composite catalysts have been formed by a three-step process, whereby the surface of aluminum electrode was pretreated upon immersion into a Pd(NH₃)₄Cl₂ solution (p-Al), was subsequently coated with a thin poly(o-aminophenol) (PoAP) layer by potentiodynamic electropolymerization of o-aminophenol and Pt and Pt alloys nano-particles were finally dispersed into the PoAP film by electrochemical methods. The electrocatalytic properties of the platinum doped (Pt/PoAP/p-Al) and Pt alloys doped (Pt–M/PoAP/p-Al, M = Ru, Ir and Sn) electrodes towards the methanol oxidation were investigated by cyclic voltammetry and compared with the electrocatalytic properties of pristine Pt and Pt particles on pretreated Al (Pt/p-Al) electrodes. The enhancement of the electrocatalytic activity of the Pt nano-particles, when Ru, Ir and Sn, are co-deposited in the polymer is also studied in detail. The effects of various parameters on the electrooxidation of methanol as well as the long-term stability of doped electrodes have also been investigated.