Nb and Fe K-edges XAFS study on the structure of supported Fe-NbN catalysts

SiO2-Supported Fe-NbN catalysts were prepared by temperature programmed reaction (TPR) method from Fe-Nb/SiO2 oxide precursor under a N2-H2 gas stream. As raising the intermediate temperature-maintaining (ITM) step temperature during the TPR, Fe species in the Fe-Nb/SiO2 catalyst was reduced to zero-valent, confirmed by Fe K-edge XAFS analysis. Although the Fe-Fe coordination number increased by elevating ITM temperature, the size of Fe cluster was still small. The Nb-N coordination number became larger, as higher the ITM temperature. The reduced Fe species effectively assisted the nitridation process of Nb.