Pt-Doped NiFe₂O₄ Spinel as a Highly Efficient Catalyst for H₂ Selective Catalytic Reduction of NO at Room Temperature

Abstract

H2 selective catalytic reduction (H2-SCR) has been proposed as a promising technology for controlling NOx emission because hydrogen is clean and does not emit greenhouse gases. We demonstrate that Pt doped into a nickel ferrite spinel structure can afford a high catalytic activity of H2-SCR. A superior NO conversion of 96% can be achieved by employing a novel NiFe1.95Pt0.05O4 spinel-type catalyst at 60 °C. This novel catalyst is different from traditional H2-SCR catalysts, which focus on the role of metallic Pt species and neglect the effect of oxidized Pt states in the reduction of NO. The obtained Raman and XPS spectra indicate that Pt in the spinel lattice has different valence states with Pt(2+) occupying the tetrahedral sites and Pt(4+) residing in the octahedral ones. These oxidation states of Pt enhance the back-donation process, and the lack of filling electrons of the 5d band causes Pt to more readily hybridize with the 5σ orbital of the NO molecule, especially for octahedral Pt(4+), which enhances the NO chemisorption on the Pt sites. We also performed DFT calculations to confirm the enhancement of adsorption of NO onto Pt sites when doped into the Ni-Fe spinel structure. The prepared Pt/Ni-Fe catalysts indicate that increasing the dispersity of Pt on the surfaces of the individual Ni-Fe spinel-type catalysts can efficiently promote the H2-SCR activity. Our demonstration provides new insight into designing advanced catalysts for H2-SCR.

Interplay between inter- and intraparticle interactions in bi-magnetic core/shell nanoparticles

“…[26,27]) as well as the significant difference between the magnetocrystalline anisotropy, K V NFO = −6.2 × 10 3 J/m 3 and K V CFO = 2 × 10 5 J/m 3 , and the relatively high value of their magnetisation M S (M S CFO = 88 A•m 2 /kg and M S NFO = 55 A•m 2 /kg) [28,29]. While most works deal with iron oxides or Mn/Zn substituted ferrites as a soft phase, only a few works are devoted to nickel ferrite in core/shell systems [4,14,30], although nickel ferrite being a promising material for catalysis [31] and spintronics [32] applications.…”

Facile Synthesis of PtxNiy Catalyst Supported on Carbon for Low Temperature H2–SCR

“…Another important point is that the oxidation state of Pt is the controlling factor for NO-H 2 reaction activity, and the lower valence state of Pt may have the higher activity . As our previous studies on Pt doped Ni–Fe spinel oxides demonstrated, the Pt with different valence states favors NO adsorption on the Pt site . The investigation on Pt/carbon black also proves that some electrons transfering from Pt to the carbon, specifically at the interface of Pt–C, can enhance the activity by tuning the electronic structure of Pt.…”

“…14 As our previous studies on Pt doped Ni− Fe spinel oxides demonstrated, the Pt with different valence states favors NO adsorption on the Pt site. 17 on Pt/carbon black also proves that some electrons transfering from Pt to the carbon, 18 specifically at the interface of Pt−C, can enhance the activity by tuning the electronic structure of Pt.…”

Mechanistic insights into NO‒H2 reaction over Pt/boron-doped graphene catalyst

“…Moreover, the low H 2 concentration (< 1%) and operation temperature suggest H 2 -SCR is a safe J o u r n a l P r e -p r o o f 4 technology. Numerous supported/doped/encapsulated noble metal catalysts were already proposed and tested for H 2 -SCR [16][17][18][19][20][21][22][23], while different reaction mechanisms were presented.…”