The Woodruff School

SUMMARY

Due to the intermittent nature of renewable energy sources, the development of a cost-effective and sustainable method of storing this vast amount of energy on an industrial scale when supply exceeds demand in the grid is an urgent need. As the cost of renewably derived electricity continues to decrease given the rapid progress in technology and economies of scale, there is a growing interest in fuels and chemicals electrosynthesis. The thrust of my Ph.D. research has focused on developing novel electrochemical technologies and processes to use renewable electricity as a driving force to convert low energy molecules (dinitrogen) to high value-added molecules (ammonia) that can be utilized as either fuel, energy storage molecules, and/or chemicals. The selectivity of dinitrogen molecules on the surface of the catalyst has been demonstrated to be one of the major challenges in enhancing the rate of photo-electrochemical nitrogen reduction reaction in aqueous solution under ambient conditions. The rational design of electrode-electrolyte in the context of photo-electrochemical systems is required to overcome the selectivity and activity barrier in NRR. The scientific thrusts of this Ph.D. dissertation to address a critical obstacle to achieving the overarching goal of distributed ammonia synthesis are as follows: Thrust 1: Materials chemistry for the synthesis of a range of heterogeneous (photo) electrocatalysts including plasmonic and hybrid plasmonic-semiconductor nanostructures for selective and efficient conversion of dinitrogen to ammonia. Thrust 2: Reactor design to study the redox processes in the photo-electrochemical energy conversion system and to benchmark the selectivity and activity of nanocatalysts toward NRR. Thrust 3: Performing Operando spectroscopy, including surface-enhanced Raman spectroscopy (SERS) to probe the reaction mechanism and to identify intermediate species relevant to NRR at the electrode-electrolyte interface. The outcomes of this dissertation generate an integrated scientific framework, combining materials chemistry, photo-electrochemistry, and spectroscopy to overcome the challenges associated with renewable energy storage and transport. It also contributes to future electrification, decarbonization, and sustainability of the modern chemical industry.

SUBJECT:	Ph.D. Dissertation Defense

BY:	Mohammadreza Nazemi

TIME:	Monday, March 9, 2020, 12:00 p.m.

PLACE:	MoSE, 3201A

TITLE:	Investigation of (Photo) Electrocatalytic Conversion of Dinitrogen to Ammonia Using Hybrid Plasmonic Nanostructures

COMMITTEE:	Prof. Mostafa El-Sayed, Co-Chair (Chem) Prof. Todd Sulchek, Co-Chair (ME) Prof. Younan Xia (Chem) Prof. Paul Kohl (ChBE) Prof. Ting Zhu (ME) Prof. Matthew McDowell (ME)

SUMMARY Due to the intermittent nature of renewable energy sources, the development of a cost-effective and sustainable method of storing this vast amount of energy on an industrial scale when supply exceeds demand in the grid is an urgent need. As the cost of renewably derived electricity continues to decrease given the rapid progress in technology and economies of scale, there is a growing interest in fuels and chemicals electrosynthesis. The thrust of my Ph.D. research has focused on developing novel electrochemical technologies and processes to use renewable electricity as a driving force to convert low energy molecules (dinitrogen) to high value-added molecules (ammonia) that can be utilized as either fuel, energy storage molecules, and/or chemicals. The selectivity of dinitrogen molecules on the surface of the catalyst has been demonstrated to be one of the major challenges in enhancing the rate of photo-electrochemical nitrogen reduction reaction in aqueous solution under ambient conditions. The rational design of electrode-electrolyte in the context of photo-electrochemical systems is required to overcome the selectivity and activity barrier in NRR. The scientific thrusts of this Ph.D. dissertation to address a critical obstacle to achieving the overarching goal of distributed ammonia synthesis are as follows: Thrust 1: Materials chemistry for the synthesis of a range of heterogeneous (photo) electrocatalysts including plasmonic and hybrid plasmonic-semiconductor nanostructures for selective and efficient conversion of dinitrogen to ammonia. Thrust 2: Reactor design to study the redox processes in the photo-electrochemical energy conversion system and to benchmark the selectivity and activity of nanocatalysts toward NRR. Thrust 3: Performing Operando spectroscopy, including surface-enhanced Raman spectroscopy (SERS) to probe the reaction mechanism and to identify intermediate species relevant to NRR at the electrode-electrolyte interface. The outcomes of this dissertation generate an integrated scientific framework, combining materials chemistry, photo-electrochemistry, and spectroscopy to overcome the challenges associated with renewable energy storage and transport. It also contributes to future electrification, decarbonization, and sustainability of the modern chemical industry.