Combinatorial Screening of Anode and Cathode Electrocatalysts for Direct Methanol Fuel Cells

Abstract

Progress in several important electrochemical technologies, including batteries, fuel cells, sensors, and electrosynthesis, is currently materials-limited. A common feature of all electrode reactions is the imbalance (i.e., loss or generation) of ions at the electrode surface. We describe in this paper a method by which excess ions in the electrode diffusion layer can be imaged, and used to identify the best electrode materials from a combinatorial array of compositions.Although in principle this method can be applied to many electrochemical problems, we have focused on finding better electrocatalysts for direct methanol fuel cells (DMFCs). The DMFC performs two half-cell reactions: oxidation of methanol, and reduction of oxygen. Two of the most important problems in DMFCs are the poor performance of the electrocatalysts, and the crossover of methanol from the anode to the cathode side of the cell. An ideal situation would be the simultaneous development of two new catalysts: an anode that oxidizes methanol at low overpotential, and a “methanol-tolerant” cathode that reduces oxygen without oxidizing methanol.Based on previously developed rules for predicting the activity of ternary alloy catalysts (Ley, et al., J. Electrochem. Soc. 1997, 144, 1543), we began searching quaternary combinations of noble metals for the anode, and ruthenium selenide-type materials for the cathode reaction. The anode and cathode reactions generate and consume protons, respectively, creating a substantial pH gradient at the electrode surface. Changes in local pH are imaged by means of an appropriate fluorescent indicator: Ni-PTP for the anode and Eosin Y for the cathode. DMFC testing confirms the utility of the screening method, in that a Pt/Ru/Os/Ir quaternary catalyst was substantially superior to the best binary and ternary catalysts prepared under similar conditions.

Synthesis of Ordered, Uniform, Macroporous Carbons with Mesoporous Walls Templated by Aggregates of Polystyrene Spheres and Silica Particles for Use as Catalyst Supports in Direct Methanol Fuel Cells

“…[12] In the present work, Pt 50 ±Ru 50 catalysts were prepared with periodically ordered bimodal porous carbon with a 317 nm macropore size and 10 nm mesopore size (referred to as POBPC(317-10) below), or with Vulcan XC-72 carbon as the catalyst support, according to a previously published method. [12,22] TEM images of the supported catalysts show a homogeneous dispersion of small, spherical, and uniform dark spots that correspond to Pt±Ru alloy nanoparticles (Fig. 3).…”

Improved catalytic activity of mixed platinum catalysts supported on various carbon nanomaterials

“…Proton exchange membrane fuel cell (PEMFC) has been regarded as an attractive and 44 efficient power supply for portable applications due to its high efficiency, high 45 specific energy density, zero pollution, and low operating temperature [1][2]. Pt-based 46 electrocatalysts, a kind of promising catalytic materials for widely-adapted PEMFC, 47 provide remarkable activity for hydrogen oxidation and oxygen reduction reactions 48 (ORR) [3].…”

Activity and Durability of Ternary PtRuIr∕C for Methanol Electro-oxidation

“…The incorporation of a third metal, such as W, Mo, Co, Ni, Sn, Os, Rh, Pb, Bi, Ir, etc., [12][13][14][15][16][17][18][19][20][21][22][23][24][25] is a typical approach to develop methanol oxidizing catalysts with improved performance. Among the ternary alloy catalysts, the PtRuIr/C system seems to be promising; the promoting effect of Ir on the methanol electro-oxidation has been studied to some extent with limited composition and temperature range.…”

“…Among the ternary alloy catalysts, the PtRuIr/C system seems to be promising; the promoting effect of Ir on the methanol electro-oxidation has been studied to some extent with limited composition and temperature range. [18][19][20][21][22][23][24][25] In this work, we conducted a systematic study on the PtRuIr/C system by preparing a series of catalysts with various Ir content and studied their electrocatalytic methanol oxidation activity at different temperatures. In addition to the initial quasi-steady state activity, the durability of the ternary catalyst was studied.…”