Dimensionally Stable Pt/Diamond Composite Electrodes in Concentrated H[sub 3]PO[sub 4] at High Temperature

Abstract

The morphological and microstructural stability, as well as the catalytic activity of a Pt/diamond composite electrode during two 1 h periods of anodic polarization in 85% H 3 PO 4 at 170°C and 0.1 A/cm 2 , were investigated. The composite electrode consisted of an electrically conducting diamond thin film support with Pt metal particles entrapped in the surface microstructure. The Pt particles range in diameter from 30 to 300 nm with a distribution of about 2 X 10 8 cm - 2 . No evidence of morphological or microstructural damage, and, more importantly, no loss of catalyst activity for hydrogen evolution or oxygen reduction was observed after the harsh electrolysis. A Pt-impregnated sp 2 carbon cloth electrode was observed to catastrophically fail during the first hour of electrolysis.