Metal Nanoparticles Anchored on Polymer-Wrapped Single-Wall Carbon Nanotubes: A Catalyst Platform for CO2 Electroreduction

Abstract

Metal nanoparticles (NPs) have been synthesized and used as highly efficient electrocatalysts for electrochemical CO2 reduction reaction (CO2RR) in recent years. Electrocatalysts with various metal sizes and morphologies have achieved remarkable improvement in CO2RR. However, the syntheses are typically energy-demanding, and the catalysts exhibit low mass activity. Ultrasmall metal NPs synthesized by a one-step process at room temperature and ambient environment stand out because of cost-effectiveness in materials and energy. In this thesis, we report a facile synthesis to produce 1-nanometer (nm) gold nanocrystals (Au NCs) in ambient conditions, which was realized by an in-situ reduction of AuCl3 on semiconducting single-walled carbon nanotube (sc-SWCNT) surface. In addition, the bipyridine (BPy) units in tube-wrapping polymers function as chelating sites for anchoring Au3+ and Au NCs. The ultrasmall size of Au NCs was achieved by a fast AuCl3 diffusion and the anchoring function of BPy units. Density functional theory (DFT) was applied to simulate Au-BPy coordination. This method also successfully applied to synthesis of monodispersed 2 nm-large copper nanoparticles (Cu NPs) with the help of thiol groups. The effect of ligands ratio and ligands side chain has been investigated systematically. Next, both Au NCs and Cu NPs on SWCNTs nanocomposites were fabricated on electrode to test their catalytic activity for CO2RR. The Au NCs exhibited a high Faradaic CO selectivity up to 86% at 25 mA/cm2 and a high mass activity up to 5.61 A/mg (Au) at 100 mA/cm2, which is the highest value reported so far in AuNCs electrocatalysts for CO2 reduction. Cu NPs showed around 10% FE of C2H4 under 150mA/cm2 after thermal treatment, while the real active sites remain unclear.