Catalysis and in situ studies of Rh₁/Co₃O₄ Nanorods in Reduction of NO with H₂

Efficient use of precious metal atoms in heterogeneous catalysis is important in chemical transformation and environmental remediation. Co ₃O₄ with singly dispersed Rh atoms, Rh₁/Co ₃O₄, was synthesized for reduction of nitric oxide with hydrogen. Studies using extended X-ray absorption fine structure (EXAFS) showed that the singly dispersed Rh atoms are bonded to surface oxygen atoms before catalysis. In situ studies using ambient pressure X-ray photoelectron spectroscopy (AP-XPS), EXAFS, and X-ray Absorption Near Edge Structure (XANES) suggested that the surface of Rh₁/Co₃O₄ with singly dispersed Rh atoms is restructured into a new geometry at 220 C in the mixture of reactant gases (NO and H₂). It forms RhCo_n nanoclusters singly dispersed in the surface layer of Co₃O ₄. The restructured catalyst, RhCo_n/Co₃O ₄ exhibits a much better catalytic performance in contrast to Rh ₁/Co₃O₄ without a restructuring. RhCo _n/Co₃O₄ is highly active for reduction of nitric oxide with hydrogen. Selectivity to the production of N₂ at 220 C is 87% and reaches 97% at 300 C. In situ studies showed this catalyst maintains its single dispersion of Rh atoms up to 300 C during catalysis.