(56l) Development of Alternative Materials to Replace Precious Metals in Sustainable Catalytic Technologies

Several reactions relevant to the progress of energy, environment and chemical manufacturing sectors involve the use of catalysts containing precious metals. The primary aim of my research is to develop: (a) precious metal-free carbon-based materials for applications in proton exchange membrane (PEM) fuel cells and electrolyzers, electrochemical synthesis of halogens and removal of halide ions from waste water, and (b) mixed metal oxide catalysts for catalytic combustion of low concentration CH₄ emitted from coal mines. My research work, therefore, involves systematic modification of catalyst synthesis procedures along with performing in-situ, ex-situ and operando characterization using a variety of spectroscopic techniques such as X-ray photoelectron spectroscopy, infrared and Raman spectroscopy, X-ray absorption spectroscopy, X-ray diffraction, Mossbauer spectroscopy and elemental analysis in conjunction with catalytic activity measurements to determine structure-property relationships in both electrocatalysis and heterogeneous catalysis.

Catalyst development for PEM fuel cells and electrolyzers:

One of the greatest challenges in electrocatalysis is the commercialization of PEM fuel cell and electrolyzer technology due to high cost and poor bifunctional characteristics of Pt and Ir catalysts required to overcome the slow kinetics of oxygen reduction (ORR) and oxygen evolution (OER) reactions, respectively. My work has established that carbon-based materials are promising electrodes for regenerative PEM fuel cells by demonstrating better bifunctional characteristics as compared to precious metal catalysts [1]. I have developed several approaches to fundamentally investigate the nature of ORR and OER active sites in these materials and used them together with density functional theory calculations to selectively tailor active sites and identified dopants to enhance their catalytic performance by ~22% [2-4].

Carbon-based catalysts for halogen production and water treatment technologies:

The energy requirement in the production of indispensable chemicals such as Cl₂ and Br₂ via electrolysis reduces by ~30% using oxygen depolarized cathode (ODC) technology. I have not only demonstrated the feasibility of using carbon-based catalysts as ODCs in electrocatalytic halogen production processes but have also identified that the versatile nature of active sites in these materials makes them active towards oxidation of halide ions in aqueous solutions [5]. This reaction finds applications ranging from halogen production to water treatment technologies.

Metal oxides for lean methane combustion:

I am also involved in developing mixed metal oxides containing Pd for catalytic combustion of low concentration CH₄ for application in technologies targeted towards reducing green-house gas emissions from coal mines. The aim is to reduce the loading of Pd in the materials while also reducing the temperature of CH₄ combustion, thereby increasing the economic feasibility of this technology and minimizing NO_x emissions. These studies will provide key insights into catalyst chemistry that can be leveraged to increase the efficiency of lean CH₄ combustion technologies.

References

[1] K. Mamtani, D. Jain, D. Dogu, V. Gustin, S. Gunduz, A.C. Co, U.S. Ozkan, Insights into oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) active sites for nitrogen-doped carbon nanostructures (CNx) in acidic media, Appl. Catal. B-Environ., 220 (2018) 88-97.

[2] K. Mamtani, D. Jain, D. Zemlyanov, G. Celik, J. Luthman, G. Renkes, A.C. Co, U.S. Ozkan, Probing the Oxygen Reduction Reaction Active Sites over Nitrogen-Doped Carbon Nanostructures (CNx) in Acidic Media Using Phosphate Anion, ACS Catalysis, 6 (2016) 7249-7259.

[3] D. Jain, K. Mamtani, V. Gustin, S. Gunduz, G. Celik, I. Waluyo, A. Hunt, A.C. Co, U.S. Ozkan, Enhancement in Oxygen Reduction Reaction Activity of Nitrogen-Doped Carbon Nanostructures in Acidic Media through Chloride-Ion Exposure, ChemElectroChem, 5 (2018) 1966-1975.

[4] Q. Zhang, K. Mamtani, D. Jain, U. Ozkan, A. Asthagiri, CO Poisoning Effects on FeNC and CN x ORR Catalysts: A Combined Experimental–Computational Study, The Journal of Physical Chemistry C, 120 (2016) 15173-15184.

[5] K. Mamtani, D. Jain, A.C. Co, U.S. Ozkan, Investigation of Chloride Poisoning Resistance for Nitrogen-Doped Carbon Nanostructures as Oxygen Depolarized Cathode Catalysts in Acidic Media, Catalysis Letters, 147 (2017) 2903-2909.