INSITU X-RAY-DIFFRACTION STUDIES OF LEAD DIOXIDE IN SULFURIC-ACID DURING POTENTIAL CYCLING

Changes in the phase composition of lead dioxide deposited on platinum have been studied via an in-situ X-ray diffraction technique using synchrotron radiation. The lead dioxide was deposited from an aqueous 0.1 M Pb(NO3)2 solution at 20-degrees-C and contained a mixture of alpha-PbO2 and beta-PbO2 phases, An electrochemical cell was used to follow phase transformations of the electrode in-situ under controlled potential conditions in 1 M H2SO4 at 20-degrees-C. Reduction to PbSO4 and reoxidation to PbO2 could be followed over a number (<50) of such redox cycles. Under the experimental conditions, the PbO2 deposit showed a relatively high degree of reversibility to PbSO4. The alpha-PbO2 phase was systematically transformed to beta-PbO2.