Catalysts for the electro‐oxidation of small molecules

Abstract

Direct oxidation‐type fuel cells (DOFCs) have attracted great interest as a primary power source for portable electronic devices, wheelchairs, vehicles, and robots because of their simple system (no additional equipment such as a fuel reformer) and ease of maintenance. The direct methanol fuel cell (DMFC) is a typical example of DOFC. Development of highly active anode catalysts for them is one of the most important issues in achieving high‐energy conversion efficiency in DOFCs. To design such new electrocatalysts, we discuss the mechanism of methanol oxidation reaction (MOR) as well as CO oxidation reaction at several electrodes, based on in situ FTIR spectroscopy and X‐ray photoelectron spectroscopy combined with an electrochemical cell (EC‐XPS). We also show changes in the MOR activities at various Pt alloy electrodes over the wide temperature range from 20 to 120 °C, obtained by using a thin‐layer flow cell under pressurized operation. The electrooxidation of methoxy fuels is briefly discussed.

Electrocatalytic oxidation of small organic molecules in acid medium: Enhancement of activity of noble metal nanoparticles and their alloys by supporting or modifying them with metal oxides

“…Significant progress has been made in this area, but there are still a number of fundamental problems to be resolved not only in fuel cell design but also in the choice of electrode materials and their utilization [1-7]. In particular, FC limitations are connected to ( i ) the poor activity/stability of conventional electrocatalysts, ( ii ) the poisoning of electrocatalytically active species by strong adsorption of intermediate products during reaction (i.e.…”

“…In particular, FC limitations are connected to ( i ) the poor activity/stability of conventional electrocatalysts, ( ii ) the poisoning of electrocatalytically active species by strong adsorption of intermediate products during reaction (i.e. CO during oxidation of alcohols); ( iii ) slow kinetics of electrode reactions including that of oxygen reduction at the cathode, and complexity and thus low efficiency of the oxidation processes that may be considered at the anode; and ( iv ) fuel cross-over through the membrane, which depolarizes the cathode and decreases its activity [1-3,8-12]. Moreover, the necessity of cost reduction and improvement of the performance of conventional Pt-based catalysts requires development of multicomponent systems capable of operating at low temperatures, certainly below 150 °C [13] but practically much lower than 100 °C.…”

“…A common approach to enhancing the reactivity of platinum involves its nanostructuring to produce electrocatalysts of high surface area and dispersion [1-4]. Further optimization of Pt-based electrocatalysts has been achieved through the formation of bi- and tri-metallic alloys such as PtCr and PtCo (oxygen reduction), PtRu (oxidation of methanol), PtPd (oxidation of formic acid), and PtSn (oxidation of ethanol).…”

“…With such systems, that have been recently discussed and reviewed [4-7], enhancement of the Pt catalytic activity has been understood in terms of changes in the electronic nature and morphology of the Pt surface and mutual interactions between alloy-forming metals. In the present review, we concentrate mostly on efficient electrocatalytic systems that poisoning of the Pt catalyst can be diminished by increasing the FC operating temperature and the roughness factor or dispersion of the Pt [1-3]. It has also been demonstrated that efficiency can be further improved by deliberate modification of the electrocatalytic interface or by promotion that utilize robust large-surface-area metal oxides (e.g.…”

Improving the Ethanol Oxidation Activity of Pt-Mn Alloys through the Use of Additives during Deposition

“…Problems associated with the costs and efficiency of fuel cells are a great barrier for industrial and consumer applications [1][2][3][4]. Direct alcohol fuel cells (DAFCs) are one of the most promising candidates for portable power applications in electronic devices and vehicles [4].…”