The performance of heterogeneous catalysts is influenced by the synthetic history of the material. Catalysts derived from layered double hydroxides (LDH) precursors have shown superior performance compared to catalysts prepared by conventional incipient wetness impregnation. However, there is a lack of studies concerning the understanding of the structural and surface dynamics, especially focusing on the importance of strong metal-support interactions (SMSI) to improve stability. We tested a series of NiCuAl LDH-derived materials with different Ni:Cu ratios in the reverse water-gas shift reaction (RWGS). We applied multiple characterization techniques for studying the pristine, activated, and spent materials after stability evaluation. The results show the importance of SMSI to prevent sintering: The activated materials showed a platelet-like morphology with homogeneously distributed NiCu metal nanoparticles (Fig. 1A). A local electronic structure investigation by electron energy-loss spectrometry unraveled the SMSI present for the Ni-containing catalyst. The catalytic activity data show that Ni promotes methanation, while Cu suppresses methanation by CO formation, similar to the results of a previous study using impregnated catalysts. The Ni:Cu(4:1) catalyst was selective and had stable performance. After 30 h on stream, a protective overlayer was found, responsible for the high stability (Fig. 1B). The metal nanoparticles were Cu-enriched near the surface (Fig. 1C) while Cu segregation was not prevented by the overlayer in the spent NiCu(1:1) catalyst (Fig. 1D). In light of our results, LDH precursors can be a basis for new formulations, particularly bimetallic nanoparticles, where intimate metal-support interactions are required to obtain stable and active catalysts.

Strong metal-support interaction on Ni-Cu-Al-LDH derived catalyst: The key of stability during RWGS reaction

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