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Carbonate‐Melt Oxidized Iridium Wire for pH Sensing
Author(s) -
Wang Min,
Yao Sheng
Publication year - 2003
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.200302723
Subject(s) - oxide , oxidizing agent , inorganic chemistry , iridium , alkali metal , hydrofluoric acid , materials science , electrode , carbonate , metal , electrochemistry , base (topology) , layer (electronics) , chemical engineering , chemistry , composite material , metallurgy , catalysis , organic chemistry , engineering , mathematical analysis , mathematics
A new approach to the preparation of an iridium oxide film for pH sensing is demonstrated. A thick, uniform and dense ceramic oxide layer was grown on the surface of an iridium wire by oxidizing the wire in a molten alkali metal carbonate at high temperature. The alkali metal ion from the carbonate melt was incorporated into the oxide, resulting in a highly stable oxide compound. After treated in acid solution, the oxide layer became hydrated. SEM, XRD, TGA and element analysis were carried out to characterize the oxide film, and a possible formula of the oxide was computed as Li 0.86 IrO 2.34 (OH) 0.76 ⋅0.39H 2 O. The electrode made with this new type of oxide film exhibited good pH sensitivity and stability, even in strong acid/base solutions, or in strong corrosive solution such as hydrofluoric acid. Furthermore, the electrode showed excellent long‐term stability over the test period of two and a half years. In addition, individual electrodes prepared from the same batch exhibited remarkable agreement with respect to potential/pH slopes and apparent standard electrode potentials. The performance of the electrodes depends on the properties of the oxide film, such as composition, hydration state and oxidation state.