Chemical and Laser Ablation Synthesis of Monometallic and Bimetallic Ni-Based Nanoparticles

Niusha Lasemi,Günther Rupprechter

doi:10.3390/catal10121453

Abstract

The catalytic properties of nanoparticles depend on their size, shape and surface/defect structure, with the entire catalyst performance being governed by the corresponding distributions. Herein, we present two routes of mono- and bimetallic nanoparticle synthesis that enable control of the structural parameters, i.e., wet-chemical synthesis and laser ablation in liquid-phase. The latter is particularly suited to create defect-rich nanoparticles. Impregnation routes were applied to prepare Ni and NiCu nanoparticles, whereas nano- and femtosecond laser ablation in liquid-phase were employed to prepare Ni and NiAu nanoparticles. The effects of the Ni:Cu ratio in impregnation and of laser fluence and liquid-medium on laser ablation are discussed. The atomic structure and (surface) composition of the nanoparticles were characterized by electron microscopic (BF-TEM, DF-TEM, HRTEM) and spectroscopic/diffraction techniques (EDX, SAED, XPS, IR), complemented by theory (DFT). The chemically synthesized bimetallic NiCu nanoparticles initially had Cu-rich surfaces, which changed to Ni-rich upon reaction. For laser ablation, depending on conditions (fluence, type of liquid), highly defective, ordered, or core/shell-like nanoparticles were produced. The case studies highlight the specific benefits of each preparation method for catalyst synthesis and discuss the potential of nanoparticles produced by pulsed laser ablation for catalytic applications.

Highlights

Methane dry reforming is a promising direction of utilizing CO2, and is a topic of intense green energy research [1,2,3]
The particles consisted of a face centered cubic Ni core (Joint Committee on Powder Diffraction Standards (JCPDS) card no. 04-0850) and a disordered shell of several nanometers (Figure 1b,c)
The Ni/NiO particles were evenly distributed on the zirconia support and their size ranged from 10 to 30 nm, but most of them had a diameter of ~20 nm

Summary

Introduction

Methane dry reforming is a promising direction of utilizing CO2 , and is a topic of intense green energy research [1,2,3]. Previous studies have emphasized using bimetallic nanoparticles (NPs), due to their modified physicochemical properties, which can be quite different from those of the single elements [4,5,6,7,8]. A central idea is to decorate the sites that lead to coking with less active metals such as Cu or Au. Wet-chemical synthesis is frequently used and the bimetallic nanoparticles often undergo structural/compositional changes during activation and reaction, resulting from the different surface energies of the applied metals. Laser ablation in liquid (LAL) may serve as an alternative method to produce binary alloy nanoparticles [9,10,11], for model studies, as structures/compositions may be obtained that are thermodynamically unfeasible and not accessible by conventional wet-chemical methods

Methods

Results

Conclusion