**2. Experimental**

#### **2.1 Pressurized electrochemical cell**

The pressurized electrochemical cell was constructed by modifying a 300 ml Parr autoclave equipped with a 200 ml glass liner, as shown in Fig. 1 (A) and (B). The working electrode was prepared by mechanically depositing high-surface-area catalysts onto a gold disk electrode of 0.5 mm in diameter, following a powder-rubbing procedure (Kucernak & Jiang, 2003), Fig. 1 (C). The mass of the catalyst layer was measured by dissolving the rubbed layer in boiling aqua regia, followed by removing the excess acid and measuring inductively

Cortright et al., 2002). The aqueous-phase reforming (APR) process eliminates the need to vaporize both water and the oxygenated hydrocarbon, which reduces the energy requirements for producing hydrogen. Moreover, the formation of CO could be minimized since the APR occurs at temperatures and pressures where the water-gas shift reaction is favorable. The APR of methanol on supported Pt over 200~265 °C results in the production

During the methanol APR, trace amount of methane is the side product and the use of more basic/neutral catalyst favors H2 production. The methanol APR indicates that sluggish methanol oxidation reaction which has plagued low temperature AMFCs, could become highly facile in alkaline/neutral media at temperatures close to 200 °C where the APR of methanol is triggered. Substantially accelerated electrooxidation of methanol would make it possible to achieve low anode overpotentials. Therefore, the investigations of the electrooxidation of methanol in an intermediate-temperature range over the methanolboiling temperature (around 80 °C) and the triggering temperature of the methanol APR (about 200 °C) would be of academic and practical importance for the development of high performance AMFC technology. This intermediate temperature range has been rarely used

Our research efforts have been focused on the investigations of fuel cell electrocatalysis in alkaline media in the intermediate-temperature range of 80 to 200 °C for accelerated anode and cathode reaction kinetics, and the development of high performance AMFCs. In this work, we have successfully developed a pressurized electrochemical cell by modifying a Parr autoclave which can be operated at pressure up to 2000 psi and at temperature up to 200 °C. An Ag/AgCl electrode has been identified as a suitable internal reference electrode with good stability in this intermediate temperature range. It has been found that the methanol oxidation and oxygen reduction reactions can be significantly accelerated in aqueous alkaline media with increasing temperature. The former is characterized by an onset overpotential of less than 0.1 V at 150 °C for substantial methanol electrooxidation at Pt. Furthermore, highly facile methanol oxidation and oxygen reduction reactions have been also achieved at non-Pt electrodes. This accelerated kinetics of both the methanol oxidation and oxygen reduction reactions provides fundamental support for the development of novel methanol fuel cells. Accordingly, high performance intermediate-temperature alkaline methanol fuel cells using Pt and non-Pt electrocatalysts have been successfully

The pressurized electrochemical cell was constructed by modifying a 300 ml Parr autoclave equipped with a 200 ml glass liner, as shown in Fig. 1 (A) and (B). The working electrode was prepared by mechanically depositing high-surface-area catalysts onto a gold disk electrode of 0.5 mm in diameter, following a powder-rubbing procedure (Kucernak & Jiang, 2003), Fig. 1 (C). The mass of the catalyst layer was measured by dissolving the rubbed layer in boiling aqua regia, followed by removing the excess acid and measuring inductively

3 2 22 *CH OH H O CO H* 3 (1)

of H2 at a usually high selectivity of around 99% as follows (Davda et al., 2005):

because of the limitation of boiling points of both methanol and water.

demonstrated.

**2. Experimental** 

**2.1 Pressurized electrochemical cell** 

coupled plasma–atomic emission spectroscopy (ICP-AES) spectra. A 15 cm length Pt wire of 0.5 mm in diameter was used as the counter electrode. Three kinds of Ag-based reference electrodes were evaluated as the internal reference electrode under our conditions by monitoring the changes of both hydrogen- and oxygen-electrochemistry on measured voltammograms for a Pt electrode in 0.5 mol dm-3 potassium hydroxide (KOH) at varying temperature. It was found that the Ag/AgCl reference provides the most reproducible results while both Ag wire quasi-reference electrode and Ag/Ag2O electrode were inapplicable. The Ag/AgCl reference electrode was introduced into a glass tube containing 0.1 mol dm-3 HCl which was separated from KOH solution in the working electrode chamber by a microporous ceramic pellet fixed at the top end of the glass tube. The potentials of the Ag/AgCl were measured versus a reversible hydrogen electrode (RHE) at varying temperature in a hydrogen atmosphere. In the following sections, all potentials reported were referred to the RHE unless otherwise stated.

Fig. 1. A pressurized electrochemical cell based on a modified Parr autoclave. Schematic diagram of the cell (A); Image of the cell (B); and Schematic structure of a working electrode (C).
