Effect of Ru and Ni nanocatalysts on water splitting and hydrogen oxidation reactions in oxygen-permeable membrane reactors

Catalytic membrane reactors based on oxygen-permeable membranes, which coupling water splitting and hydrogen oxidation reactions and oxygen separation into a single unit, has been regarded as a promising route to produce high-purity hydrogen. Surface reactions including water splitting and hydrogen oxidation reactions play important roles in the hydrogen separation process. Catalysts with high catalytic activities towards these two reactions are highly desired. In this work, in-situ exsolved Ru and Ni nanocatalysts were prepared and tested for hydrogen separation in four membrane reactors. The Ru element incorporates into the lattice of Ce0.85Sm0.15O1.925 (SDC) support after being prepared in air but it is exsolved from the SDC lattice to form 3-5 nm nanoparticles after being reduced in hydrogen. The Ru nanoparticles prefer to stay at the step-faceting of the support. Meanwhile, the strong metal-support interactions (SMSI) between Ru and SDC support has been certified. The SMSI benefits the stabilization of Ru nanoparticles at elevated temperatures, thus the Ru/SDC catalyst shows high catalytic activity towards both hydrogen oxidation and water splitting reactions. A doubled hydrogen separation rate of 21.6 mL cm(-2) min(-1) was obtained at 900 degrees C when using the Ru/SDC catalyst compared with Ni-based catalysts. Experimental results show that the catalysts on both sides have great impacts on the hydrogen separation rate, indicating both the water splitting reaction and hydrogen oxidation reaction are potential rate determining steps.