11/08/2022
By Fuqiang Liu

The Francis College of Engineering invites you to attend a doctoral dissertation defense in Mechanical Engineering entitled "Liquid-junction Photoelectrochemical Cell for Direct Solar Energy Storage.”

Ph.D. Candidate: Guanzhou Lin
Date: Tuesday, Nov. 22, 2022
Time: 1 to 3 p.m. (US EDT)
Location: This will be a virtual defense via Zoom. Those interested in attending should contact guanzhou_lin@student.uml.edu and advisor Fuqiang_liu@uml.edu at least 24 hours prior to the defense to request access to the meeting.

Committee Chair: Fuqiang Liu, Ph.D., Associate Professor, Mechanical Engineering, UMass Lowell (Advisor)

Dissertation Committee Members:

  • Agar Ertan, Associate Professor, Mechanical Engineering, UMass Lowell
  • Xinfang Jin, Assistant Professor, Mechanical Engineering, UMass Lowell
  • Kwok-Fan Chow, Associate Professor, Chemistry, UMass Lowell

Abstract:

To efficiently utilize solar energy, it is crucial that this abundant renewable energy source could be converted into storable energy carriers, such as solar fuels or other energy-rich products. These energy carriers can be produced via either an indirect route in which electricity is involved as an intermediate step, or a direct route that utilizes highly active photogenerated charge carriers without any intermediate energy conversion step. Direct routes have developed rapidly over the past decade, but previous studies were almost exclusively limited to discovery of new materials and artificial photosynthetic systems, and reversible redox systems for direct solar energy storage. So far, the underlying advantages of the direct routes still remain unaddressed.

The objective of this PhD study is to investigate the fundamental difference between direct and indirect routes in solar energy conversion using a new photoelectrochemical energy storage cell (PESC) as a model device. This PESC utilized CH3NH3PbI3 (MAPbI3) perovskite in combination with the Benzoquinone (BQ)-Ferrocene (Fc) redox system. It has been verified that when integrated with BQ-Fc redox couples the created liquid junction is capable of directly modulating the charge transfer at the perovskite/electrolyte interface. Besides, the fundamental properties of perovskite were explored in the PESC system by photoelectrochemical characterization. Fabrication of dense perovskite films that is compatible with the non-aqueous redox species has been discussed. Furthermore, to investigate the key processes that determine the photo charging kinetics, two models of a PESC and a redox flow battery (RFB) were developed based on the same cell configurations and electrochemical/transport characteristics. It was founded that a steep electric field in the photoelectrode could effectively force the reaction products to drift away from the reaction zone, thus creating a constant reaction driving force to improve the solar energy conversion efficiency at low-current operating conditions. Different perovskite photoelectrode fabrication processes, electrode construction, and cell parameters have been explored in this dissertation to further improve the photoelectrochemical performance. We conclude that the prior development in the great wealth of solid-state perovskite solar cell literature can be conveniently adopted to the design and optimization of the photoelectrochemical energy storage cell.