06/11/2024
By Danielle Fretwell

The Francis College of Engineering, Department of Chemical Engineering, invites you to attend a Doctoral Dissertation defense by Zhengyang Yang on "Synthesis and Characterization of Copper-Based Nanoneedle Array by Template-Assisted Electrodeposition and Their Applications in Electrochemical Catalysis and Sensing."

Candidate Name: Zhengyang Yang
Degree: Doctoral
Defense Date: Monday, June, 24, 2024
Time: 9 to 11 a.m. (EST)
Location: Perry Hall 215

Committee:

  • Advisor Zhiyong Gu, Professor/Chair, Chemical Engineering, University of Massachusetts Lowell
  • Fanglin Che, Assistant Professor, Chemical Engineering, University of Massachusetts Lowell
  • Kwok-Fan Chow, Associate Professor/Graduate Coordinator, Chemistry, University of Massachusetts Lowell

Brief Abstract:
Cu has been extensively studied as electrocatalyst and electrochemical sensors due to its unique chemical and physical properties like the electron transfer ability, unique binding ability, and extraordinary catalytic activity. Typically, Cu was found as a unique electrocatalyst generating a number of hydrocarbons, aldehydes, and alcohols during the electrochemical CO2 process (CO2RR). The hydrocarbon production via CO2RR provides a sustainable strategy to offset carbon emission, mitigate global warming and store renewable energy. However, the high overpotential for CO2 activation and low selectivity to specific C2+ hydrocarbon products compromise the energy efficiency and commercial feasibility of the CO2RR over Cu. Formic acid is gaining attention as an efficient hydrogen carrier and a promising energy fuel for direct formic acid fuel cells (DFAFCs) of portable power systems. The production of formic acid through electrochemical CO2RR can serve as a carbon-neutral process and effectively offset the carbon emissions. Cu also exhibits a noteworthy sensing ability for several environmental contaminants such as nitrate, nitrile, and sulphites. Nitrate is identified as one of the predominant nitrogen species due to the extensive usage of nitrogen-based chemicals in various industries. The excessive concentration of nitrate leads to eutrophication, triggering the health concerns of human society due to the toxicity of nitrate and other nitrogen-based compounds like nitrite, nitric oxide, and N-nitroso. The electrochemical sensing of nitrate provides a fast and continuous way for nitrate detection with small and simple instrumentation. Cu has been explored as an active material for nitrate sensing via its redox activity for nitrate reduction, while the Cu-based sensor frequently suffered from a lower sensitivity for the practical applications.

This work features the usage of Cu-based nanoneedle array aiming for both CO2RR and nitrate sensing applications. First, the Cu-based nanoneedle array can be fabricated via a facile electrodeposition method with the highly ordered vertical alignment. The active surface area can be enhanced via the nanoscale feature of needles, and the morphology of Cu nanoneedle/nanowire can be adjusted via the deposition current. The structure effect of the nanoneedles benefits from a high edge sites density and active facet exposure. The structure analysis was conducted over scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD). The potential electrochemical application of Cu nanoneedle was explored for CO2RR with focus on selective formic acid-production and nitrate sensing via a Cyclic Voltammetry method. With the nanoneedle array electrode, the electrochemical performance was significantly improved with higher electrochemical surface area, lower charge transfer resistance, and reduced onset potential, as compared to Cu foil electrodes. The result shows that the surface modification of aminothiol can enhance the CO2RR products selectivity like ethylene and ethanol on Cu foil, and formic acid on Cu nanoneedle array. The sensing of nitrate via the Cu-based nanoneedle array exhibited a high sensing performance compared to the reported works using the Cu-based nanostructure electrodes, with a detecting range matching the regulation of the U.S. Environmental Protection Agency (EPA). Overall, the Cu-based nanoneedle shows the potential as a versatile electrocatalyst for a wide range of sustainable applications.