Reaction of PbS Surfaces with Oxygen

Abstract

The reaction of fresh PbS surfaces with oxygen was studied by crushing the sample in a clean, degassed system. The reaction of PbS with oxygen was noted at room temperature, but the rates were conveniently measurable only above about 100°C. The reaction did not stop at monolayer coverage and showed no inflection in rate at that extent of reaction. The rate of the reaction was found to be directly proportional to the area of the PbS surface, and the pressure of oxygen over the surface, and inversely proportioned to the thickness of the reaction product layer for extents of reaction in excess of 0.4 mole O2 reacted per mole PbS on surface initially. Although the main products of the interaction were SO2 and lead oxides, considerable amounts of CO2 were detected, in spite of attempts to purify the PbS by recrystallization from the vapor. The complexities of the reaction of PbS with oxygen, and probably the performance of PbS-film devices, are related to a considerable extent to the difficulties in obtaining clean PbS surfaces for reaction. The extent of these difficulties does not appear to have been fully appreciated in earlier work.