Pt-TiO2 loaded on activated carbon was studied as an active and stable catalyst to HI decomposition for H2 formation in the sulfur-iodine process. Although the activity of TiO2-loaded catalyst was slightly lower HI conversion than that of CeO2 loaded one, the higher stability against HI decomposition reaction was achieved and almost equilibrium conversion was sustained over ~65 h examined. Moreover, effects of Rh or Ir addition on HI conversion were studied and it was found that Pt-Rh bimetallic system was highly active and stable to HI decomposition. Scanning transmission electron micrograph observation suggested that the increased HI decomposition activity was assigned to the increased dispersion of Pt particles. High dispersion state of Pt was sustained after HI decomposition at 773 K by addition of Rh. Since the formation of PtI4 was suggested by X-ray photoelectron spectroscopy measurement during HI decomposition, increased stability by addition of Rh seems to be assigned to the high chemical stability of Rh against iodine. Almost the equilibrium HI conversion on Pt-Rh-TiO2/M563 was sustained over 300 hours at 673 K.
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