Ni in CNFs: Highly Active for Nitrite Hydrogenation

Abstract

Nickel “hairy” foam, consisting of carbon nanofibers (CNFs) grown on the surface of nickel foam, were synthesized and tested for nitrite hydrogenation. The results showed that nickel “hairy” foam is catalytically active in the absence of any noble metal, which is attributed to the formation of nickel particles with high carbon content during CNF growth. These C-doped nickel particles showed catalytic properties similar to those of noble metals, but were easily deactivated as a result of oxidation treatments. This deactivation is partially attributed to nickel passivation, which is reversible by reducing with H2 at room temperature in the gas or liquid phase. In addition, oxidation treatment also caused partial removal of the carbon dissolved in the nickel particles, causing irreversible deactivation. Increasing severity of the oxidation treatment induced slower reactivation via reduction, as well as lower steady-state activities after reactivation. This irreversible deactivation is attributed to the decreased concentration of dissolved carbon. Therefore, nickel “hairy” foam is a promising hydrogenation catalyst, provided it is protected against oxygen.

H2-Based Membrane Catalyst-Film Reactor (H2-MCfR) Loaded with Palladium for Removing Oxidized Contaminants in Water

“…Suspended catalysts, the most-studied form, typically enabling considerably higher catalytic activities than immobilized catalysts due to less mass-transfer resistance, , cannot be applied for long-term continuous treatment because they are subject to be washed out . Conventionally immobilized catalysts on packed supporting particles , or structured interfaces , suffer from rapid deactivation and/or leaching of the immobilized catalysts during continuous operation.…”

Hydrogenation of aqueous nitrate and nitrite with ruthenium catalysts

“…Although years of effort have been invested in improving the activity, endproduct selectivity, and long-term stability of Pd-based bimetallic catalysts [31,45] (and to a lesser extent Pt-based catalysts [36,46]), deployment of practical catalytic treatment systems remains limited, in large part, due to high costs of Pd [47]. Precious metal-free catalysts based on Ni have been explored [15,48,49], but instability in aqueous matrices [50], and serious concerns about the associated leaching of dissolved Ni 2+ [51] and the pyrophoric nature of highly active Raney Ni [52] have limited further development efforts.…”

Enhancement of Interfacial Charge Transportation Through Construction of 2D–2D p–n Heterojunctions in Hierarchical 3D CNFs/MoS2/ZnIn2S4 Composites to Enable High‐Efficiency Photocatalytic Hydrogen Evolution

“…In addition, their surfaces contain abundant functional groups, which can act as preferred nucleation sites for the crystallization of semiconductor photocatalysts. The development of MoS 2 /CNFs, [ 35 ] Co/CNFs, [ 36 ] Ni/CNFs, [ 37 ] Cu/CeO 2 /CNFs, [ 38 ] and ZnIn 2 S 4 @CNFs [ 39 ] show great promise for photocatalytic H 2 evolution. Nevertheless, the weak interface bonding, reduced active sites, and unsatisfactory interfacial transportation efficiency of charge carrier inevitably occur when directly loading catalytic materials onto the CNFs substrate.…”