MgO-Templated Mesoporous Carbon as a Catalyst Support for Polymer Electrolyte Fuel Cells

Abstract

An MgO-templated mesoporous carbon, CNovel ® , was employed as a catalyst support for the cathode of polymer electrolyte fuel cells (PEFCs) after modifying its dimensional, crystalline, surface and porous structures and the electrochemical oxygen reduction reaction (ORR) activities were examined by the thin-film rotating disk electrode (RDE) method and as well as the membrane electrode assembly (MEA) method. Although the catalytic activity of Pt on CNovel ® was comparable with that on a non-porous carbon, Vulcan ® , in the RDE configuration without Nafion ® , Pt/CNovel showed a considerably higher activity than Pt/Vulcan in the MEA condition with Nafion ® . The mechanism inducing this difference was discussed from the results of electrochemical surface area and sulfonic coverage measurements which suggested that Pt particles on inside pores of CNovel ® are not covered with Nafion ® ionomer while protons can still reach those Pt particles through water network. The MEA performance in the middle and high current-density regions was drastically improved by heat-treatment in air, which modified the pore structure to through-pored ones.

Operando X-ray Absorption Spectroscopic Study on the Influence of Specific Adsorption of the Sulfo Group in the Perfluorosulfonic Acid Ionomer on the Oxygen Reduction Reaction Activity of the Pt/C Catalyst

“…These reports suggested that the adsorption of a sulfo group anion from the side chain of Nafion blocked the active site of Pt . A similar behavior has been observed for Pt-based catalysts (Pt/C), but the extent of decrease in the ORR activity varies depending on the carbon structure. − The properties of the carbon support are crucial in reducing the poisoning effect of perfluorosulfonic acid ionomers and in improving the catalyst performance. − Catalysts prepared from porous carbons with 4–7 nm opening pores show excellent ORR activities and transport properties . Shinozaki et al.…”

Catalysts for Polymer Membrane Fuel Cells

“…Remy et al [2] used an interesting approach to reduce the dimensionality of the repeating unit of the carbon support material by replacing traditional carbon black with graphene and carbon nanotubes. Kamitaka and coworkers [3] uniquely explored a sacrificial nanostructured metal-oxide template to create the support architecture, which was then deployed successfully in a PEMFC.…”

Does an Ionomer Penetrate a Carbon Mesopore? Free-Energy Analysis Using Molecular Dynamics Simulations

“…They also lower the voltage during high-current-density operations. , Combined experimental and theoretical analyses have shown that high interfacial oxygen-permeation resistance at the ionomer–catalyst interface causes the voltage drop. − To reduce these negative effects, two approaches have been proposed: molecular design of the ionomer and optimal control of the ionomer distribution. The former involves imidization of the sulfonic acid group, incorporation of ring-structured backbone matrices, − and shortening of the side chains, , whereas the latter involves applications of an ionomerless catalyst layer such as the nanostructured thin film, dopamine coating to block anion adsorption, and applications of mesoporous carbon supports. ,,− …”

“…Introducing mesopores into carbon supports is a promising approach for suppressing ionomer–catalyst contacts. ,,− Past studies have shown that the ORR catalytic activity is enhanced by carbon supports with nanometer-scale pores. ,, Transmission electron microscope (TEM) observations have demonstrated that ∼60% of the Pt nanoparticles’ surface area exists in the mesopores, , and electrochemical measurements have shown that anion adsorption on the catalysts in the mesopores is suppressed. , These analyses demonstrate that mesoporous carbon support suppresses the poisoning of active sites by ionomers. In addition, electrochemical characterizations indicate that oxygen-transport resistance can be reduced by introducing oxygen-accessible mesopores into the carbon supports. , Suppression of catalyst-particle growth has also been reported as a side effect . Motivated by these results, intensive studies have addressed the control of pore sizes ,, and the locations of deposited catalyst particles .…”

“…In addition, electrochemical characterizations indicate that oxygen-transport resistance can be reduced by introducing oxygen-accessible mesopores into the carbon supports. , Suppression of catalyst-particle growth has also been reported as a side effect . Motivated by these results, intensive studies have addressed the control of pore sizes ,, and the locations of deposited catalyst particles . Another significant approach to controlling the ionomer distribution in the catalyst layer is the optimization of the fabrication process of the catalyst layer.…”