Oxides on the Silver Electrode. Part 2. X-Ray Diffraction Studies of the Working Silver Electrode

摘要

Silver electrodes were examined in 20-50% KOH using a cell permitting simultaneous x-ray diffraction and electrochemical studies. Highly oriented smooth rolled sheet silver developed randomly oriented Ag on its surface during early cycles. Charge-discharge capacity increased to a maximum as surface area increased. AgO crystal size and amount formed varied inversely with charging current density with high charging rates giving tight coatings of small AgO crystals that limited further oxidation. Reactions took place initially at the outer surface of the electrode with oxidation to Ag2O and AgO and reduction to Ag2O and Ag occurring by formation of distinct crystals rather than by expansion or contraction of preexisting crystal lattices. Discharge capacity at the AgO/Ag2O potential plateau depended more on surface area than on quantity of AgO. A slow discharge produced smoother Ag surfaces, lowering capacity of the next cycle. There was never evidence of a suboxide, oxidation state higher than AgO, solid solution, or alloy of oxygen and silver. (Author)