NMR as a probe for molecular adsorption on metal surfaces in electrochemical environments and at electrified interfaces

The $\sp{13}$C and $\sp{15}$N NMR spectra of surface adsorbed cyanide on a platinum electrode have been obtained for the first time. The in situ electrostatic field effect on $\sp{13}$C and $\sp{15}$N chemical shifts and the temperature effect on their relaxation times over a wide temperature range have also been investigated. T$\sb1$ measurements for both $\sp{13}$C and $\sp{15}$N show a single exponential decay of the magnetization, indicating a predominance of only one surface adsorbed species. T$\sb1$ rates of $\sp{13}$C is proportional to temperature from 10K to 273K, with a Korringa relationship T$\sb1\cdot$T $\sim$ 138 s$\cdot$K. A complex Korringa behavior is observed for $\sp{15}$N: over the temperature range from 50K to 200K, T$\sb1\cdot$T is $\sim$ 4300 s$\cdot$K, much larger than that of $\sp{13}$C; but at above 200K, T$\sb1\cdot$T is $\sim$ 3000 s$\cdot$K, indicating a small structural rearrangement. The above T$\sb1\cdot$T results show that the conduction electron of platinum is contributed to the T$\sb1$ relaxations and the carbon atom is attached to the platinum surface. T$\sb2$ measurements of $\sp{13}$C in deuterated/non-deuterated electrolytes show that the proton in H$\sb2$O contributes to T$\sb2$ relaxation. Temperature-dependent T$\sb2$ relaxation rates in D$\sb2$O provide information on surface diffusion. It has been confirmed that T$\sb1$, T$\sb2$, peak shift and breadth of $\sp{13}$CN on platinum, acquired in a sealed cell at room temperature, are the same as those obtained in an ENMR-cell under full potentiostatic control, within experimental error. It has also been found that both $\sp{13}$C and $\sp{15}$N surface resonances respond to the applied electric field. Further, the adsorption of CH$\sb3$CN on platinum in these electrochemical environments has been investigated by choosing specific nuclei as probe for the relaxation time measurements.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Wu, Jianjun

Contributors dc:contributor

• Wieckowski, Andrzej

• Chemistry, Analytical
• Chemistry, Physical
• Engineering, Chemical

Statement dc:rights

• Copyright 1996 Wu, Jianjun

Language dc:language

eng

Identifier

9780591199680
AAI9712486
(UMI)AAI9712486

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/19399