Stabilizing Catalytically Active Nanoparticles by Ligand Linking: Toward Three-Dimensional Networks with High Catalytic Surface Area

Abstract

A general approach for the linking of Pt nanoparticles (NPs) with bifunctional amine ligands (organic molecules with two amine groups) is presented that allows for the preparation of NP catalysts without inorganic supports and high densities of the catalytically active metal. Advantage was taken of the use of "unprotected" NPs, which enables us to prepare different ligand-functionalized NPs from the same particle batch and thus to relate changes of the resulting material properties exclusively to the influence of the ligand. Three bifunctional ligands with similar functional groups (amines) but different hydrocarbon skeletons were used and compared to monofunctional ligands of similar molecular structures (alkyl and aryl amines) showing significantly different material properties. Monofunctional molecules with minor steric demand cover almost completely the NP surface and lead to two-dimensional assembling of the NPs. In contrast, the use of bifunctional amine ligands leads to the formation of porous, three-dimensional NP networks (ligand-linked NPs) with a high density of ligand free surface atoms, thus enabling for the application as catalytic materials. The stabilizing effect of bifunctional ligands serves as an alternative to the use of inorganic support materials and enables for catalytic applications of ligand-linked NP networks.

Untangling the Role of the Capping Agent in Nanocatalysis: Recent Advances and Perspectives

“…Indeed, because of their high-dispersed state, metal nanoparticles in solution tend to spontaneously agglomerate and coagulate, therefore need to be stabilized [4]. The stabilization of MNPs can be achieved by immobilization on a support or by wrapping them in an organic ligand shell [13][14][15].…”

1-Naphthylamine functionalized Pt nanoparticles: electrochemical activity and redox chemistry occurring on one surface

“…28 In contrast to pure Pt NPs (Fig. 4 Although no ECSA could be determined for fresh NA-Pt by CO stripping experiments, the presence of a characteristic Pt-CO band at 2015 cm À1 in the NA-Pt spectrum reveals the presence of ligandfree surface sites. 1b) does not reveal the characteristic features of Pt NPs.…”

“…4 For preparation, dispersing, and storage of NA-Pt NPs see 2.1-2.3. 4 For preparation, dispersing, and storage of NA-Pt NPs see 2.1-2.3.…”

“…3,4 At a full monolayer of ligands (denoted to as ligand coverage = 1) all surface atoms are blocked and no catalytically active surface area can be determined. 1,2 For ligand-functionalized NP catalysts the accessibility of surface atoms is determined by the steric demand and the coverage of the ligand.…”

Three dimensional PEDOT nanowires network

“…In the case of intrinsically conducting polymers (ICP), nanostructuration plays an important role. Usually, ICP are semiconductors and have been used in the development of many electronic devices such as solar cells [12], transistors [13], thermoelectric modules [14][15][16], organic light emitting diodes [17] and supercapacitors [18][19][20]. A well defined 3D network of nanowires can be the key in the next generation of electrodes for supercapacitors applications.…”