Effects of Fuel Concentrations, Catalyst Loadings and Activation on the Performance of Direct Formic Acid Fuel Cell (Dfafc) Stack

Abstract

An air-breathing stack for a direct formic acid fuel cell (DFAFC) was designed, fabricated and evaluated. The DFAFC stack consisted of six cells arranged in a hexagonal arrangement and each single cell contained a pair of stainless steel current collectors, a membrane electrode assembly (MEA) and a cathode end-plate. A fuel reservoir was located at the center which supplied formic acid supply to the anode of each cell. The effects of fuel concentration, palladium (Pd) loading at the anode and activation on DFAFC performance and long term operation were evaluated. DFAFC stack performance increased with increasing fuel concentration and a stable power up to 200 mW at 2.4 V was achieved for passive and ambient conditions at a 7 M fuel concentration. Catalyst loading had a slight effect on DFAFC performance, where 4 mg cm -2 Pd loading was best for 7 M fuel operation. During long-term operation, the DFAFC stack could be operated for 27 hours without adding more fuel and less than a 20 % reduction in performance during operation. MEA reactivation with deionized water technique was required for immediate recovery of stack performance.Keywords: stack, activation, passive direct formic acid fuel cell, membrane electrode assembly Abstrak Tindanan pasif udara bagi sel bahan api asid formik langsung (DFAFC) direka bentuk, difabrikasi dan diuji. Tindanan DFAFC mengandungi enam sel yang dibentuk secara susunan heksagon. Setiap sel mempunyai sepasang pengumpul arus, himpunan membran elektrod (MEA) dan plat penghujung katod. Takungan bahan api ditempatkan di tengah yang mana akan membekalkan asid formik ke setiap sel. Kesan kepekatan bahan api, kandungan palladium (Pd) di anod dan pengaktifan terhadap prestasi dan jangka masa panjang DFAFC dikaji. Prestasi tindanan DFAFC meningkat dengan peningkatan kepekatan bahan api dan kuasa yang stabil sehingga 200 mW dicapai pada 2.4 V dan 7 M kepekatan bahan api dalam keadaan pasif dan persekitaran. Kandungan mangkin mempunyai kesan minimum terhadap prestasi DFAFC yang mana kandungan Pd 4 mg cm -2 merupakan kandungan terbaik bagi pengoperasian 7 M kepekatan asid formik. Sepanjang pengoperasian jangka masa panjang, tindanan DFAFC boleh beroperasi selama 27 jam tanpa menambah bahan api di dalam takungan dan kurang daripada 20 % pengurangan prestasi tindanan. Pengaktifan MEA menggunakan teknik nyahion air diperlukan bagi pemulihan segera prestasi tindanan DFAFC.Kata kunci: tindanan, pengaktifan, sel bahan api asid formik langsung pasif, himpunan membran elektrod ISSN -2506 Mohd Shahbudin et al: EFFECTS OF FUEL CONCENTRATIONS, CATALYST LOADINGS AND ACTIVATION ON THE PERFORMANCE OF DIRECT FORMIC ACID FUEL CELL (DFAFC) STACK 878Introduction With respect to direct liquid fuel cells (DLFCs), a direct formic acid fuel cell (DFAFC) is a promising alternative to direct methanol fuel cell (DMFC) and direct ethanol fuel cell (DEFC) cells. The main advantages of DFAFC are a relatively high electro-catalytic oxidation rate [1,2] and low crossover rate for the fuel [3 -5] and has the potential...

Improving the electrocatalytic activity for formic acid oxidation of bimetallic Ir–Zn nanoparticles decorated on graphene nanoplatelets

“…The theoretical open-circuit voltage (OCV) of DFAFC (1.45 V) is higher than that of proton exchange membrane fuel cell (PEMFC) (1.23 V) and direct methanol fuel cell (DMFC) (1.21 V) [6,7]. Formic acid exhibits lower fuel crossover through the Nafion membrane, which allows the use at higher fuel concentration up to 20 M, compared with only 2 M in methanol [8,9]. The reduction of fuel crossover is caused by the repulsion between formate ions in formic acid and sulfuric group in the surface of Nafion membrane [10].…”

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