Self-regeneration of a Ni-Cu alloy catalyst during a three-way catalytic reaction

Cr-Fe-Ni-Cu Quaternary Nanostructure as a Substitute for Precious Metals in Automotive Three-Way Catalysts

The replacement of precious metals (Rh, Pd, and Pt) in three-way catalysts with inexpensive and earth-abundant metal alternatives is an ongoing challenge. In this research, we examined various quaternary metal catalysts by selecting from six 3d transition metals, i.e., Cr, Mn, Fe, Co, Ni, and Cu, equimolar amounts (0.1 mol each), which were prepared on the Al₂O₃ support (1 mol Al) using H₂ reduction treatment at 900 °C. Among 15 combinations, the best catalytic performance was achieved by the CrFeNiCu system. Light-off of NO-CO-C₃H₆-O₂-H₂O mixtures proceeded at the lowest temperature of ≤200 °C for CO, ≤300 °C for C₃H₆, and ≤400 °C for NO when the molar fraction of Cr in Cr _x Fe_0.1Ni_0.1Cu_0.1 was around x = 0.1. The activity for CO/C₃H₆ oxidation was superior to that of reference Pt/Al₂O₃ catalysts but was less active for NO reduction. The structural analysis using scanning transmission electron microscopy and X-ray absorption spectroscopy showed that the as-prepared catalyst consisted of FeNiCu alloy nanoparticles dispersed on the Cr₂O₃-Al₂O₃ support. However, the structural change occurred under a catalytic reaction atmosphere, i.e., producing NiCu alloy nanoparticles dispersed on a NiFe₂O₄ moiety and Cr₂O₃-Al₂O₃ support. The oxidation of CO/C₃H₆ can be significantly enhanced in the presence of Cr oxide, resulting in a faster decrease in O₂ concentration and thus regenerating the NiCu metallic surface, which is active for NO reduction to N₂.

Positive effects of a halloysite-supported Cu/Co catalyst fabricated by a urea-driven deposition precipitation method on the CO-SCR reaction and SO2 poisoning

Cu/Co catalysts were prepared on halloysite nanotube supports by a urea-driven deposition–precipitation method for CO oxidation and the selective catalytic reduction of NO (CO-SCR).

The catalytic decomposition of nitrous oxide and the NO + CO reaction over Ni/Cu dilute and single atom alloy surfaces: first-principles microkinetic modelling

Density functional theory calculations and microkinetic modelling reveal that well-engineered Ni/Cu dilute alloys are promising for the catalytic reduction of NO by CO.

Self-Regeneration Process of Ni-Cu Alloy Catalysts during a Three-Way Catalytic Reaction-An Operando Study

It is important to understand the reduction processes of mixed metal oxides or metal oxide interfaces in three-way catalytic reactions toward replacing the currently used high-cost Pt group metal catalysts. The redox behavior of simple Ni-Cu alloy catalysts, which exhibit high catalytic activity and durability during a three-way catalytic reaction, was studied by operando X-ray absorption spectroscopy (XAS). The operando XAS analyses revealed that Ni-Cu species changed from the NiO-Cu₂O to Ni-Cu alloy and vice versa under reductive and oxidative conditions, respectively. The real-time monitoring of the oxidation states of Ni and Cu species indicated that the Cu species assisted the reduction of Ni species, in agreement with the density functional theory-based study of NiO reduction by carbon monoxide in the presence of metallic Cu nanoparticles.