The Chemical Catalysis Program in the Chemistry Division and the Office of International Science and Engineering's (OISE) East Asia and Pacific Program support Professor Michael Mirkin of CUNY Queens College in the US, in collaboration with Professor Bin Ren of Xiamen University in China. The proposal for which this award was granted was submitted in response to Program Announcement NSF 09-608: International Collaboration in Chemistry between US investigators and their Counterparts Abroad (ICC). The research of Professor Ren is supported by the National Natural Science Foundation of China. The researchers propose to prepare catalytic metal clusters by electrodeposition at nanoelectrodes and to produce even smaller (a few atoms) metal deposits in thin layer nanocells. The first part of this project will focus on electrodeposition at nanoelectrodes (research conducted by the CUNY group). Mercury, used as a model to validate the methodology, and solid catalytic metals (e.g., Ru, Pd, Ag, Co, and Ni) will be deposited on Au and Pt nanoelectrodes of various sizes (from 5 nm to 200 nm). The size and shape of deposited metal nanostructures will be characterized by electrochemistry, scanning electrochemical microscopy (SECM) and scanning electron microscopy (SEM). The mechanism of nucleation/growth of metals on nanoelectrodes will be investigated. Preliminary results point to the new features of these processes that could not be observed in conventional experiments at macroscopic electrodes. Meanwhile, the Xiamen group will develop methodology for using modified disk-type Au nanoelectrodes as tip-enhanced Raman spectroscopy (TERS) tips to generate the Raman active species in real time. Next, the groups will focus on electrodeposition and TERS experiments in nanometer-sized thin layer cells (nano-TLCs). The catalytic activities of deposited metal clusters for several electrocatalytic reactions (hydrogen evolution reaction [HER], oxygen reduction reaction [ORR], and oxidation of methanol) will be characterized by electrochemical methods and a SECM-TERS hybrid technique. The combination of SECM and TERS will provide much more comprehensive information about electrocatalysis than that obtained from electrochemical and spectroscopic experiments individually.

The proposed research intends to address fundamental aspects of the electrocatalysis of extremely small metal clusters. It should contribute to better understanding of the electrocatalytic process and its current limitations. In addition, it is expected to advance knowledge of nanoelectrochemistry, scanning electrochemical microscopy (SECM) and tip enhanced Raman Spectroscopy (TERS). In addition to fundamental importance, the anticipated results will have significant implications for fuel cells and other alternative energy systems relying on electrocatalysis. The results of this research will be broadly disseminated through publications and professional presentations. The proposed activities will enhance the infrastructure for research and education at CUNY by stimulating the development of new instrumentation and forging the new international partnership. The undergraduate and graduate students involved in this project will gain valuable experience in multidisciplinary fundamental research. The proposed international collaboration will provide additional training opportunities for students in both research groups and expose them to a wide range of electroanalytical and spectroscopic methods, as well as theoretical and computational approaches. Being a part of the international collaborative project will prepare them for future leadership positions in research, both nationally and internationally.

Project Report

The performed research improved our understanding of electrochemical nucleation/growth processes at nanometer-sized electrodes. First atomic force microscopy (AFM) images of metal nanoelectrodes were obtained, and the first nanoelectrochemical experiments under in situ AFM control have been carried out. This approach was used to monitor in real time the changes resulting from nucleation/growth processes at the nanoelectrode surface. The combination of nanoelectrochemistry and AFM imaging also enabled the study of unexpected and very efficient dissolution of Pt at moderate negative potentials during oxygen reduction reaction in water and organic media that was unrelated to oxide formation. New types of electrochemical nanoprobes were developed, including platinized electrochemical sensors prepared by electrodepositing Pt black on carbon nanoelectrodes. An attractive feature of these electrodes that distinguishes them from previously reported platinized Pt probes—their small physical size—makes them suitable for detecting and quantifying reactive oxygen and nitrogen species in biological cells. Another type of sensor—"a nanosampler"—was developed for sampling small volumes (attoliter to picoliter) of solution and rapid electrochemical analysis of sampled redox species. It can be useful for electrochemical measurements in biological vesicles, catalyst nanopores, and inside working batteries or fuel cells. The catalytic responses of single Au nanoparticles and atomic gold clusters were investigated by immobilizing them on carbon nanoelectrodes. The effects of the immobilization methodology on catalytic behavior were observed. The developed approach should be useful for studying the effects of nanoparticle size, geometry, and orientation on its electrocatalytic activity. This project provided opportunities for multidisciplinary research to four graduate students and a postdoctoral fellow. They were trained in electrochemistry, elecrocatalysis and nanoscience. These students gave oral and poster presentations at national and international meetings and participated in preparation of research papers. They also visited the laboratories of our collaborators at Xiamen University, China and Drexel University, Philadelphia and performed joint experiments with their groups. Two students obtained PhD degrees and started postdoctoral studies. A senior visiting scientist from India has been doing research closely related to this project in the PI's laboratory.

Agency
National Science Foundation (NSF)
Institute
Division of Chemistry (CHE)
Application #
1026582
Program Officer
Timothy E. Patten
Project Start
Project End
Budget Start
2010-10-01
Budget End
2014-09-30
Support Year
Fiscal Year
2010
Total Cost
$355,400
Indirect Cost
Name
CUNY Queens College
Department
Type
DUNS #
City
Flushing
State
NY
Country
United States
Zip Code
11367