Semiconducting oxides: effects of solid and solution properties on dissolution kinetics of cobaltous oxide

Abstract

The dissolution of p-type CoO has been investigated as part of the study of electronic and surface structural factors controlling dissolution kinetics of semiconducting oxides. Electron microscopy of surface morphology changes on annealing showed sintering but no preferential growth of particular low-index faces. Surface attack by acid produced considerable surface roughening but no evidence for formation of particular low surface energy faces. Increasing prior annealing temperature caused lowering of the dissolution rate per unit surface area. A linear relationship between log(rate) and pH with slope –0.6 was found. There is a general trend for the dissolution rate of CoO to be decreased with increasing oxidation potential of the solution. Doping with Li, La and Cr resulted in increased dissolution rates in all cases. The influence of defect structure, atomic surface detail, surface charge-carrier depletion and surface states are examined in relation to these observations.