Preparation And Characterization Of The Novel Catalysts For Hi Decomposition In The Iodine-sulfur Cycle

Iodine-sulfur thermochemical water splitting cycle is considered one of the mostpromising alternative methods for massive hydrogen production with high efficiencyand without CO2emissions. As the key reaction for hydrogen production of this process,the study of decomposition of HI has drawn much attention. Catalysts are always usedto catalyze this reaction to advance the efficiency of this reaction.In this study, several series of catalysts supported on activated carbon (AC) wereprepared by the impregnation-reduction method and electroless plating, respectively.Their catalytic activities were compared for HI decomposition in a fixed bed reactor at400and500°C under atmospheric pressure. Their differences in structures, morphologyand surface areas were characterized by XRD, TEM and BET, respectively.Firstly, eight kinds of monometallic catalysts (Pt, Pd, Ni, Rh, Ir, Co, Ru and Ag)supported on AC were prepared by the impregnation and reduction method. The resultsshowed that Pt and Pd catalysts had the highest activity and the best stability. Then,three kinds of metal (Pd, Ni, Rh) were introduced into the Pt catalyst to preparePt-based bimetallic catalysts by the co-impregnation and reduction method. Comparedwith Pt monometallic catalysts, bimetallic catalysts showed high activity and evenbetter stability.Secondly, a series of bimetallic Pt–Pd catalysts supported on AC were prepared bythe co-impregnation and reduction method. Furthermore, their thermal stabilities werealso investigated by calcinating at500°C for2h under N2atmosphere. The results ofactivity tests showed that the composition of bimetallic Pt–Pd catalysts played theimportant role in dictating the catalyst activity. Among the Pt, Pd and bimetallic Pt–Pdcatalysts, the2.5Pt–2.5Pd/AC showed the best catalytic performance for thedecomposition of HI. The results of thermal stability tests showed that the bimetallicPt–Pd catalyst had the higher stability than the monometallic Pt and Pd catalysts. Then,a series of bimetallic Pt–Ir catalysts supported on AC were prepared by theco-impregnation and reduction method. The2.5Pt-2.5Ir/AC had the best activity andwas used in a long-term catalytic performance test for70h. The results showed that thebimetallic Pt-Ir catalyst possessed good activity maintenance.Thirdly, four kinds of bimetallic Pt-Ni catalysts supported on activated carbon were prepared by electroless plating. The results showed that the bimetallic Pt-Ni/ACcatalysts are promising catalysts for HI decomposition because of their high activity andgood stability, especially at high reaction temperature.Finally, a series of bimetallic Ni–Pd catalysts supported on active carbon wasprepared by electroless plating method. The catalyst of1Ni–1Pd/AC showed the bestcatalytic performance for the decomposition of HI. The bimetallic Ni–Pd catalyst hadthe higher stability in specific surface area and structure than monometallic Pd catalystduring HI decomposition.Based on the above studies, it could be concluded that the bimetallic catalysts aremore promising catalysts for HI decomposition than the monometallic Pt catalyst.