The Woodruff School

SUMMARY

Nitrate (NO3-) is the world’s most widespread surface and ground water contaminant that causes adverse effects on human health such as methemoglobinemia (“blue baby syndrome”) and cancer. While most nitrate removal strategies occur through the use of ion exchange resins, these approaches are not sustainable as waste disposal of the brines remains a critical challenge. Electrocatalytic NO3- remediation; however, is one emerging approach for nitrate removal which does not produce waste as NO3- is converted directly to inert dinitrogen (N2) gas. The main challenge with electrocatalytic NO3- reduction is the low activity and selectivity of the NO3- to N2 because this conversion is a rate-determining step and results in undesirable products such as nitrite (NO2-) and ammonium (NH4+). Here, we propose to focus efforts on understanding electrocatalytic behavior of precious metals such as palladium (Pd) and identify highly active and selective catalysts depends on various Pd facets.
We first develop Pd shape-controlled nanoparticles and demonstrate their electrocatalytic activity of nitrate reduction and nitrite reduction in alkaline electrolyte through conducting rotating ring disk electrode (RRDE).
To achieve an more efficient activity and selectivity for the denitrification, we introduce copper (Cu) metals as a secondary metal on the surface of Pd nanocube by using the underpotential deposition (UPD) and solvothermal methods. The electrochemically deposited and doped Cu atoms mainly promote the reduction of NO3- to NO2- and Pd (100) facet catalyze the reduction of NO2- to N2. Under the metal desorption area at the UPD method, we can control the surface coverage of metals by sweeping stopped at selected potentials. Conducting RRDE tests enabled the measurement of improved activity and selectivity of NO3- to N2 using shape-controlled Pd that contain surface modifications. This work demonstrates that electrocatalytic nitrate/nitrite reductions are an important approach to mitigate environmental impacts associated with removing harmful NO3- and NO2- from water.

SUBJECT:	Ph.D. Proposal Presentation

BY:	JeongHoon Lim

TIME:	Thursday, May 28, 2020, 1:30 p.m.

PLACE:	https://bluejeans.com/343116750?src=calendarLink, N/A

TITLE:	Electrochemical Remediation of Nitrate/Nitrite-contaminated Water by Palladium-based Electrocatalysts

COMMITTEE:	Dr. Marta C. Hatzell, Chair (ME) Dr. Seung Woo Lee (ME) Dr. Hailong Chen (ME) Dr. Younan Xia (Chem) Dr. Andrew J. Medford (ChBE)

SUMMARY Nitrate (NO3-) is the world’s most widespread surface and ground water contaminant that causes adverse effects on human health such as methemoglobinemia (“blue baby syndrome”) and cancer. While most nitrate removal strategies occur through the use of ion exchange resins, these approaches are not sustainable as waste disposal of the brines remains a critical challenge. Electrocatalytic NO3- remediation; however, is one emerging approach for nitrate removal which does not produce waste as NO3- is converted directly to inert dinitrogen (N2) gas. The main challenge with electrocatalytic NO3- reduction is the low activity and selectivity of the NO3- to N2 because this conversion is a rate-determining step and results in undesirable products such as nitrite (NO2-) and ammonium (NH4+). Here, we propose to focus efforts on understanding electrocatalytic behavior of precious metals such as palladium (Pd) and identify highly active and selective catalysts depends on various Pd facets. We first develop Pd shape-controlled nanoparticles and demonstrate their electrocatalytic activity of nitrate reduction and nitrite reduction in alkaline electrolyte through conducting rotating ring disk electrode (RRDE). To achieve an more efficient activity and selectivity for the denitrification, we introduce copper (Cu) metals as a secondary metal on the surface of Pd nanocube by using the underpotential deposition (UPD) and solvothermal methods. The electrochemically deposited and doped Cu atoms mainly promote the reduction of NO3- to NO2- and Pd (100) facet catalyze the reduction of NO2- to N2. Under the metal desorption area at the UPD method, we can control the surface coverage of metals by sweeping stopped at selected potentials. Conducting RRDE tests enabled the measurement of improved activity and selectivity of NO3- to N2 using shape-controlled Pd that contain surface modifications. This work demonstrates that electrocatalytic nitrate/nitrite reductions are an important approach to mitigate environmental impacts associated with removing harmful NO3- and NO2- from water.