National Science Foundation     |     Directorate for Engineering  (ENG)
Division of Chemical, Bioengineering, Environmental, & Transport Systems  (CBET)
 
CBET Research Highlights 
Notable Accomplishments from CBET Awards
 
 
CBET Research Highlight - Part A - Simplified Non-technical

7644 - Novel Catalyst Reduces Cost of Hydrogen Production

Prashant Kumta  -  University of Pittsburgh

Outcome or Accomplishment:  Researchers at University of Pittsburgh have developed a more efficient catalyst that will reduce the cost of carbon-free hydrogen production.

Prashant N. Kumta Image 1
  Figure 1.  Scanning Electron Microscopy image of RuO2-70wt%SnO2 with 10wt%F surface showing smooth mud crack morphology effective for optimal performance.
 
Credit:  Prashant N. Kumta, University of Pittsburgh, Pittsburgh, PA

Impact:  The newly developed catalyst uses less expensive materials than the traditional noble metal oxide catalyst.&nbsb; Reducing the cost of hydrogen production may significantly contribute to the hydrogen economy.  Hydrogen, which may be used as a fuel in proton exchange membrane fuel cells to power vehicles and also provide stand alone power to buildings offers a good solution to the current energy and environmental concerns.

Explanation/background:  There is a critical need to identify methods to produce, store, and transport hydrogen so that fuel cells can be harnessed for practical applications in hybrid as well as all electric fuel cell driven automobiles.  Electrolysis is the process used to obtain hydrogen from water, however is quite costly.  Production of hydrogen, by means of water electrolysis, requires a high amount of electric energy and uses expensive materials as electrocatalysts.  Professor P.N. Kumta with his co-workers from the University of Pittsburgh, Pennsylvania, have synthesized and characterized a novel family of electrocatalysts demonstrating high electrocatalytic activity with low production cost.  This class of materials could offer a feasible solution to hydrogen production thus offering a solution to the world wide need for complex energy storage.



CBET Research Highlight - Part B - Engineering Technical Information

7644 - Cost Effective Catalysts for Hydrogen Generation

Prashant Kumta  -  University of Pittsburgh


Background:  Noble metals and noble metal oxides are known for their electro-catalytic activity for proton exchange membrane fuel cells (PEMFC) and water electrocatalysis for the generation of carbon free hydrogen.  They are therefore currently used as the gold standard for water electrolysis.  However, the cost of noble metals makes the commercial implementation of these catalysts prohibitively expensive.  The high cost therefore provides the impetus to search for stable catalyst supports to minimize the loading while also enhancing the electrocatalytic activity.  Unfortunately, the highly acidic pH ~0 and the electrochemical potential window of ~1.23 V provides an extremely corrosive environment and most materials tend to be unstable under these highly stringent electrochemical conditions prevalent in water electrolysis.  It is desirable therefore that these catalyst supports exhibit high electronic conductivity combined with excellent chemical and electrochemical stability in harsh water electrolysis conditions to exhibit the desired charge transfer characteristics needed for optimal electrocatalytic activity. Very few materials exhibit the desired electrical conductivity and electrochemical stability at 1.8-2.0V.  Group IV oxide particularly, SnO2 is known to exhibit the desired electrochemical stability but exhibits however moderate electronic conductivity.  Thus, there is a need to further improve its electronic conductivity to enhance the efficiency of the electro-catalytic activity and minimize the catalyst loading.  The present study attempts to conduct a fundamental experimental and theoretical study to identify a new class of different SnO2 based materials that likely exhibit improved electrochemical and electronic properties for electrolysis of water.

Results:  1.  In the present study, the effect of SnO2 and F doped SnO2 (SnO2:F) as a support for noble metal oxide RuO2 electro-catalyst has been investigated.  Theoretical quantum-mechanical study showed that small amount of fluorine up to 10 wt% of F may drastically improve the electronic conductivity of SnO2.  Thus, better electrochemical activity of RuO2-SnO2:F is expected compared to undoped RuO2-SnO2.  A solid solution of 30% of RuO2 and 70% of SnO2 with different amount of fluorine has been synthesized in Prof. Kumta's laboratory.  The electrochemical activity of pure RuO2 and RuO2-70wt.% SnO2 with F content (0-10wt.%) is demonstrated in Figure B1.  From the figure it can be clearly seen that the electrochemical performance of fluorine-doped Ru-Sn oxide is higher than undoped RuO2-70wt.% SnO2 and almost identical to that of pure RuO2.  This novel compound RuO2-70wt.% SnO2 with 10%F contains less than one third of very expensive RuO2 resulting in substantial cost reduction of the material with not much compromise in the electrochemical activity.
 
                 2. The team's quantum-mechanical theoretical study conducted in this phase of the study related to this novel electrocatalyst showed that small addition of fluorine to the RuO2-SnO2 solid solution improves the electronic conductivity which positively affects the overall electrocatalytic performance of the material.  Figure B2 demonstrates dependence of the electronic conductivity (in fact, the electronic density of states at Fermi level) on the compositional amount of fluorine doped SnO2 in the material.  It can be seen from the calculations that an excellent conductivity in almost all range of RuO2 - SnO2:F concentrations up to 80 wt% of SnO2:F is maintained, beyond which the conductivity drastically drops down although still remaining metallic.  These first principles calculations provide an explanation for the high catalytic activity of fluorine doped Ru-Sn oxide solid solutions with substantial reduction of the expensive noble RuO2.  Scanning electron microscopy image of RuO2-70wt.% SnO2 with 10%F catalyst surface is shown in Figure 1.  A smooth surface with mud-crack morphology is presented which also contributes to the excellent catalytic performance shown in Figure B1.
 
                 3. The team was also successful in developing cost effective simple chemical approaches utilizing solutions of metal salts of the corresponding transition metals and noble metals.  The mixed salt solutions were then spin coated onto the metal substrates followed by heat treatments to moderate temperatures of 400oC to generate the smooth mud crack morphology shown in Figure B2.  This morphology appears to be ideal for generating good wetting of the electrocatalyst with the electrolyte enabling good contact.  The excellent electronic conductivity coupled with the electrochemical stability and activity together results in the system exhibiting similar electrochemical activity as the parent noble metal oxide.
 
Summary:  Novel electrocatalyst systems with reduced noble metal content based on solid solutions of SnO2 were identified based on first principles theory and simple wet chemical sol-gel approaches.  The dimensionally stable anode structures exhibit catalytic activity comparable to the parent noble metal oxide.  The compositions containing 70wt% SnO2 appear to exhibit the optimal catalytic activity matching that of RuO2.  First principles DFT calculations show that introduction of fluorine to the extent of 10 wt% is useful for maintaining the electronic conductivity of the solid solutions similar to that of the parent noble metal oxide.  Higher fluorine contents lead to lowering of the electronic conductivity while also marginally affecting the cohesive energies of the oxides.

Scientific Uniqueness:  The NSF-funded research is unique because it addresses: a) novel cost effective chemical approaches for generation of high surface area RuO2 catalyst structures on stable catalyst supports;  b) role of bulk and surface microstructure and composition on the electrochemical stability and the electrocatalytic response;  c) fundamental understanding of electrolytic mechanisms occurring at catalytic surface by means of various theoretical approaches of computational Physics and Chemistry.  The approach provides a unique combination of experimental and theoretical approaches to identify new catalyst solid solutions exhibiting catalyst performance similar to that of the noble metal oxide.  The theoretical calculations are an ideal framework for providing the scientific explanations to the excellent experimental observations of electrocatalytic performance.  The two approaches therefore complement each other providing the ideal synergy to the scientific study.

This research highlight addresses CBET Strategic Outcome Goals as follows:
 
- 1Primary Strategic Outcome Goal:  Discovery:  The NSF-funded research is aimed at development of new efficient electrocatalysts for water electrolysis demonstrating high catalytic activity along with low production cost.  In addition, quantum-mechanical theoretical approaches allowed the research team to reveal the scientific origins of high catalytic activity of Ru-Sn based electrocatalysts.  The funded research thus provides the ideal experimental backed theoretical framework for discovering novel electrocatalysts and catalyst supports for water electrolysis exhibiting performance matching that of the traditionally used noble metal catalysts.  Thus new electrocatalyst compositions were identified that lead to reduction in noble metal content by almost 70%.  The excellent electrochemical performance was demonstrated by experiment.  Theoretical calculations have shown the scientific basis for the excellent activity exhibit by these novel electrocatalysts.  The continued theoretical studies will provide the scientific explanation for the rational design of new cost effective electrocatalysts and catalyst supports.
 
- 2Secondary Strategic Outcome Goal:  Learning:  This project has provided training and research experience to one PhD candidate graduate student from Chemical Engineering, and one undergraduate student in the Mechanical Engineering and Materials Science departments at the University of Pittsburgh, Pittsburgh, Pennsylvania.

Transformative Research:  The research is potentially transformative because up until now the gold standard for electrocatalysts and catalyst supports for water electrolysis has been noble metal oxides.  The theoretical studies of determining the electronic conductivity and the cohesive energies have provided guidelines for the experimentalists to design next generation electrocatalysts with reduced noble metal contents without compromising the electrochemical activity.  As a result, catalysts have been identified with reduction in noble metal content by ~70%.  It is anticipated that these continued theoretical studies will provide the framework for complete elimination of the noble metal oxide which will be a revolutionary change and a paradigm shift in the development of new non noble metal catalyst design.

Intellectual Merit:  1.  The theoretical and experimental studies will help in synthesizing a new class of nano-crystalline mixed metal oxide catalyst supports exhibiting desirable electronic conductivity and electrochemical catalytic properties.
 
                            2.  The concepts developed will help obtain a good understanding of the underlying electrochemical processes and the influence of nano-scale materials structure and microstructure on the electrochemical stability and activity.
 
                            3.  The combination of theory and experiments will lay the foundation for the design and development of novel catalyst supports for the generation of carbon free hydrogen using electrolysis of water.

Broader Impacts of this research include:
 
- 1Benefits to society:  Significant benefits to society can be envisaged since the proposed research can offer a feasible solution to hydrogen production thus offering a solution to the world wide complex energy storage needs.  The study can lead to identification of reduced noble metal and even completely eliminate noble metal thus conceivably providing a very cost effective solution to the generation of hydrogen and making green fuel and green energy storage technology a reality.  Thus the following benefits can be seen:
        A.  Enabling the cost effective generation of hydrogen.
        B.  Ability to fabricate fuel cells with cost effective hydrogen production to power clean electric vehicles.
        C.  The technology can also be used to generate high surface area materials exhibiting good electronic conductivity and red-ox characteristics for generation of supercapacitors for clean electric vehicles.
 
- 2Broadening participation of underrepresented groups:  The present studies offer an excellent opportunity for minority women and individuals from underrepresented groups to participate in the research activity.  The on-going existing collaboration with North Carolina Agriculture and Technical University (NCAT) through the recently funded NSF-Engineering Research Center (ERC) helps to recruit minority individuals into the graduate program.
 
- 3Advancing discovery and understanding while promoting teaching, training, and learning:  Web-based audio-visual electrochemistry tools are under development for providing good easy understanding of the complex concepts to local high school students, undergraduates and graduate students.  Furthermore, local high school students will be given hands-on-experience by participating in projects in the PI's laboratory and present their work in a competitive workshop.  Successful candidates will also be given an opportunity to attend fuel cell and hydrogen related conferences.  The project has already enabled one graduate student, a minority undergraduate student and a high school minority student to participate in the research activities of the project.
 
- 4Enhancing the infrastructure for research and education:  The NSF funded project has led to the establishment of the center for complex engineered multifunctional materials (CCEMM) within the Swanson school of engineering at the University of Pittsburgh.  The center provides opportunity for acquiring new electrochemical instrumentation for students to conduct cutting edge research.  At the same time the project has enabled fostering the existing partnership with NCAT enabling the participation of minority students.
 
- 5Results disseminated broadly to enhance scientific and technological understanding:  Results of the research study will be published in leading peer reviewed scientific journals and will also be periodically presented at national and international conferences. The students and faculty have already actively participated and presented their findings at the Electrochemical Society meetings held in Vancouver, Las Vegas, Boston and the upcoming meeting in Seattle.  In addition, the results are being submitted for publication in peer reviewed journals of high impact factor.


 
Program Director:
 
 
 
Ram Gupta
CBET Program Director - Energy for Sustainability
     
NSF Award Number:   0933141
     
Award Title:   Novel Catalyst Supports for Water Electrolysis: Experimental and Theoretical Studies
     
Principal Investigator:   Prashant Kumta
     
Institution Name:   University of Pittsburgh
     
Program Element Code:   7644
     
CBET Research Highlight:   Fiscal Year 2012
     
Approved by CBET on:   Pending
     
     


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This Research Highlight was Updated on 8 August 2012.