Carbon-supported and unsupported Pt anodes for direct borohydride liquid fuel cells

Abstract

Investigations have been conducted on direct borohydride liquid fuel cells (DBFCs) based on the electro-oxidation of sodium borohydride, NaBH4. A comparative study on the use of carbon-supported and unsupported Pt anode catalysts for DBFCs has been made. The effects on anode and fuel cell performance of catalyst loading, binder content, fuel concentration, and pH of supporting solution dissolving NaBH4 are studied. A maximum power density of 44.2 mW cm(-2) to unsupported catalyst of 7 mg cm(-2) (under room temperature and air breathing) has been obtained. Cell performance by using the anode with 1.50 mg cm(-2) carbon-supported Pt anode catalyst is comparable to that by using the anode with 6 mg cm(-2) unsupported Pt anode catalyst. It is found that the carbon-supported catalysts are more cost effective and have higher catalytic activity than the unsupported catalysts. The coulombic efficiencies calculated from the energy density (theoretical capacity 5880 vs. measured capacity) for unsupported and carbon-supported Pt anode catalysts are 62.3 and 68.1%, respectively. The DBFC developed in this work has better performance than the conventional fuel cells using hydrocarbon liquid fuels like methanol. (C) 2004 The Electrochemical Society.