[en] This report contains a literature review for electrochemical evaluation of solid state pH sensors. The requirements of pH electrode for geochemical fluids in a nuclear waste repository site are rather difficult to fulfill, that is, the electrode must have stability at temperatures up to 250/degree/C, low ionic and redox interferences, corrosion resistance, and robustness. Among the potential electrode materials, the IrO₂ emerges as the most promising because of its consistent near Nernstian response and its electrochemical behavior at the IrO₂-solution interface is essential in order to optimize the performance of IrO₂ electrodes for pH sensing at high temperatures and pressure. This report reviews theoretical models of the oxide-solution interfaces based on the theory of the electric double layer. Electrochemistry of IrO₂ films with emphasis on the properties of anodic films is summarized. A plan for pH testing of sputtered iridium oxide films is summarized. A plan for pH testing of sputtered iridium oxide films (SIROF) for geochemical measurements at a Tuff Repository is described. 80 refs