Synthesis and Characterization of Os and Pt−Os/Carbon Nanocomposites and their Relative Performance as Methanol Electrooxidation Catalysts

Abstract

Thermal treatment of cis-(2,2‘-bipyridine)2OsCl2, (η6-cymene)2Os2Cl4, or [(bpy)2Os(μ-bpm)PtCl2][CF3SO3]2/Vulcan carbon powder composites under solely reductive conditions affords Os or Pt−Os/carbon nanocomposites consisting of metal nanoparticles highly dispersed on the carbon support. Nanocomposites containing ca. 35−50 wt % metal with metal nanocrystals of ca. 5−6 nm average diameter are formed. Evaluation of the performance of these nanocomposites as methanol electrooxidation catalysts in direct methanol fuel cells and in an electrochemical cell designed for combinatorial testing reveals that, although the Os/carbon nanocomposites and the Pt−Os alloy/carbon nanocomposite give open circuit potentials indicative of thermodynamically favorable methanol oxidation, the kinetics of these oxidations are too low to be of practical importance. Unfortunately, the Os-containing electrocatalysts prepared by this synthesis strategy did not exhibit high performance for methanol oxidations as predicted by theoretical computations.

An overview of unsolved deficiencies of direct methanol fuel cell technology: factors and parameters affecting its widespread use

“…Therefore, the utility of a second metal that can act as a promoter by providing oxygenated species at lower potentials for oxidative removal of adsorbed CO has been investigated [67,68]. Subsequently, many binary and multimetallic Pt-based alloy compositions, such as Pt/Ru, Pt/Os, Pt/Sn, Pt/Mo, Pt/Ir, Pt/Ru/Sn/W and Pt/Ru/Sn, have been proposed for the purpose of improving the electrooxidation of CH 3 OH [67][68][69][70][71][72][73][74][75][76][77]. However, the use of Pt in combination with non-noble metals as an anodic catalyst material for CH 3 OH electro-oxidation poses two major limitations: (i) uncertainty over long-term stability; and (ii) uncertainty and time dependence of the available active surface area due to a leaching out effect.…”

High dispersion and electrocatalytic activity of Pd/titanium dioxide nanotubes catalysts for hydrazine oxidation

“…The fabrication and electrocatalytic properties of metal catalysts deposited on nanomaterials have been intensely investigated in recent years, motivated by the desire to improve the performance of fuel cells [1][2][3][4][5][6][7][8][9][10]. Among many possible combinations of metal catalyst and inert support, palladium (Pd) and palladium group metals-based nanocomposites are one of the most widely employed catalysts for the electrochemical reactions in fuel cells operating with acid or alkaline electrolytes [5,6,8].…”

Direct Electrochemistry of Hemoglobin Immobilized on Carbon‐Coated Iron Nanoparticles for Amperometric Detection of Hydrogen Peroxide

“…Recently, nanosized carbon-metal composites have attracted great interest because of their unique physical and chemical properties and the importance of these materials as catalysts [18,19]. Commercial carbonmetal nanocomposites containing Pt, Pd, etc., have been commonly used as electrooxidation catalysts in direct methanol fuel cells [20,21]. Shen et al have investigated the electrochemical properties of C/Fe nanocomposite and used them to fabricate a mediator-free glucose biosensor successfully [22].…”