Chemical and Biological Engineering ETDs

Publication Date

6-26-2015

Abstract

Copper nanoparticles of porous, controlled structure were synthesized using the sacrificial support method (SSM). The precursor weight percent (wt%) of copper (Cu) and fumed silica (EH-5) was varied to determine the optimum ratio for this material. The precursors were reduced at i) 350°C in a 7% H2 atmosphere and ii) at 250°C in a 100% H2 atmosphere. The specific surface areas of the nanoparticles was measured by Brunauer-Emmett-Teller N2 absorption. The morphologies and widths of the nanoparticles were confirmed by imaging the nanoparticles by scanning electron microscopy (SEM). The bulk composition of the nanoparticles was determined by X-ray diffraction (XRD). Results of these characterizations are discussed in detail. The nanoparticles with a precursor Cu content of 5 and 10wt% exhibited the most controlled morphology with smallest particle widths when reduced at 250°C in 100% H2 (21.5 ± 6.7 nm and 29.3 ± 11.3 nm, respectively) and at 350°C in 7% H2 (29.8 ± 9.4 nm and 60.5 ± 21.5 nm, respectively). Carbon dioxide (CO2) electroreduction (CER) on the Cu nanoparticles synthesized by SSM was confirmed with rotating disk electrode experiments (RDE) using cyclic voltammetry at 25°C in CO2 saturated 0.1M potassium bicarbonate solution (KHCO3) at atmospheric pressure. The electrochemical stability of these nanoparticles was tested via bulk electrolysis for one hour at -1.2, -1.6, and -2.2 V vs. Ag/AgCl in kinetic and diffusion limited regimes. All nanoparticles exhibited activity towards CER and displayed excellent stability for at the potentials tested. The current densities observed during bulk electrolysis at -2.2 V vs. Ag/AgCl were between ca. -23 and -40 mA cm-2 for the nanoparticles reduced at 350 °C in 7% H2 atmosphere and ca. -12 and -20 mA cm-2 for the nanoparticles reduced at 250°C in 100% H2 atmosphere. The magnitude and stability of these particles makes them ideal candidates for further studies that will determine their relative efficiencies towards specific CER products by liquid and gas quantification.

Keywords

electrochemistry, sacrificial support method, carbon dioxide electroreduction, copper, nanoparticles

Document Type

Thesis

Language

English

Degree Name

Chemical Engineering

Level of Degree

Masters

Department Name

Chemical and Biological Engineering

First Committee Member (Chair)

Atanassov, Plamen

Second Committee Member

Serov, Alexey

Third Committee Member

Datye, Abhaya

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