(230a) Platinum Group Metal Catalysts for Sulfur-Based Thermochemical Water Splitting Cycles

Thermochemical cycles can be used to split water through a series of chemical reactions where the net result is the production of hydrogen and oxygen at much lower temperatures than direct thermal decomposition. The sulfur-based family of thermochemical cycles appears promising for producing hydrogen from water. These cycles employ a high-temperature sulfuric acid decomposition reaction step. The reaction produces oxygen and generates SO₂, which is used in other reaction steps of the cycles. The reaction takes place from 750 to 900°C, or higher, and is facilitated by heterogeneous catalysts. The high-temperature, harsh chemical reaction conditions present a significantly challenging environment for catalytic materials. Current catalyst stability studies performed at the Idaho National Laboratory (INL) have found that the most active catalysts for the acid decomposition reaction, platinum supported on porous metal oxides, are not stable at the desired reaction temperatures. In this work we explore the effect of other platinum group metals, including Pd, Rh, and Ru, on the stability of platinum catalysts.