Prashant Kumta

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Papers by Prashant Kumta

Fluorine substituted (Mn,Ir)O2:F high performance solid solution oxygen evolution reaction electro-catalysts for PEM water electrolysis

RSC Advances, 2017

Identification and development of high performance with reduced overpotential (i.e. reduced opera... more Identification and development of high performance with reduced overpotential (i.e. reduced operating electricity cost) oxygen evolution reaction (OER) electrocatalysts for proton exchange membrane (PEM) based water electrolysis with ultra-low noble metal content (i.e. reduced materials cost) is of significant interest for economic hydrogen production, thus increasing the commercialization potential of PEM water electrolysis. Accordingly, a novel electrocatalyst should exhibit low overpotential, excellent electrochemical activity and durability superior to state of the art noble metal based electro-catalysts (e.g. Pt, IrO 2 , RuO 2 ). Herein, for the very first time to the best of our knowledge, exploiting first-principles theoretical calculations of the total energies and electronic structures, we have identified a reduced noble metal content fluorine doped solid solution of MnO 2 and IrO 2 , denoted as (Mn 1Àx Ir x )O 2 :F (x ¼ 0.2, 0.3, 0.4), OER electrocatalyst system exhibiting lower overpotential and higher current density than the state of the art IrO 2 and other previously reported systems for PEM water electrolysis. The doped solid solution displays an excellent electrochemical performance with a lowest reported onset potential to date of $1.35 V (vs. RHE), $80 mV lower than that of IrO 2 ($1.43 V vs. RHE) and $15 fold (x ¼ 0.3 and 0.4) higher electrochemical activity compared to pure IrO 2 . In addition, the system displays excellent long term electrochemical durability, similar to that of IrO 2 in harsh acidic OER operating conditions. Our study therefore demonstrates remarkable, $60-80% reduction in noble metal content along with lower overpotential and excellent electrochemical performance clearly demonstrating the potential of the (Mn 1Àx Ir x )O 2 :F system as an OER electro-catalyst for PEM water electrolysis.

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Intracellular trafficking pathways involved in the gene transfer of nano-structured calcium phosphate-DNA particles

Biomaterials, Oct 1, 2011

Nano-structured calcium phosphate (NanoCaP) particles have been proven to be a powerful means of ... more Nano-structured calcium phosphate (NanoCaP) particles have been proven to be a powerful means of non-viral gene delivery. In order to better understand the mechanisms through which NanoCaPs-mediated mammalian cell transfection is achieved, we have sought to define the intracellular trafficking pathways involved in the cellular uptake and intracellular processing of these particles. Previous work has indicated that NanoCaP-DNA complexes are most likely internalized via endocytosis, however the subsequent pathways involved have not been determined. Through the use of specific inhibitors, we show that endocytosis of NanoCaP particles is both clathrin-and caveolae-dependent, and suggest that the caveolaer mechanism is the major contributor. We demonstrate colocalization of NanoCaP-pDNA complexes with known markers of both clathrin-coated and caveolar vesicles. Furthermore, through the use of quantitative flow cytometry, we present the first work in which the percent internalization of CaP-DNA complexes into cells is quantified. The overall goal of this research is to foster the continued improvement of NanoCaP-based gene delivery strategies.

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Early differentiation patterning of mouse embryonic stem cells in response to variations in alginate substrate stiffness

Journal of Biological Engineering, Apr 9, 2013

Background: Embryonic stem cells (ESCs) have been implicated to have tremendous impact in regener... more Background: Embryonic stem cells (ESCs) have been implicated to have tremendous impact in regenerative therapeutics of various diseases, including Type 1 Diabetes. Upon generation of functionally mature ESC derived islet-like cells, they need to be implanted into diabetic patients to restore the loss of islet activity. Encapsulation in alginate microcapsules is a promising route of implantation, which can protect the cells from the recipient's immune system. While there has been a significant investigation into islet encapsulation over the past decade, the feasibility of encapsulation and differentiation of ESCs has been less explored. Research over the past few years has identified the cellular mechanical microenvironment to play a central role in phenotype commitment of stem cells. Therefore it will be important to design the encapsulation material to be supportive to cellular functionality and maturation. Results: This work investigated the effect of stiffness of alginate substrate on initial differentiation and phenotype commitment of murine ESCs. ESCs grown on alginate substrates tuned to similar biomechanical properties of native pancreatic tissue elicited both an enhanced and incrementally responsive differentiation towards endodermal lineage traits. The insight into these biophysical phenomena found in this study can be used along with other cues to enhance the differentiation of embryonic stem cells toward a specific lineage fate.

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Study of fluorine doped (Nb,Ir)O2 solid solution electro-catalyst powders for proton exchange membrane based oxygen evolution reaction

Materials Science And Engineering: B, Oct 1, 2016

High surface area (~300 m 2 /g) nanostructured powders of (Nb 1-x Ir x )O 2 and (Nb 1-x Ir x )O 2... more High surface area (~300 m 2 /g) nanostructured powders of (Nb 1-x Ir x )O 2 and (Nb 1-x Ir x )O 2 :10F (~100 m 2 /g) have been examined as promising oxygen evolution reaction (OER) electrocatalysts for proton exchange membrane (PEM) based water electrolysis. Nb 2 O 5 and 10 wt.% F doped Nb 2 O 5 powders were prepared by a low temperature sol-gel process which were then converted to solid solution (Nb,Ir)O 2 and 10 wt.% F doped (Nb,Ir)O 2 [(NbIr)O 2 :10F] electrocatalysts by soaking in IrCl 4 followed by heat treatment in air. Electro-catalyst powders of optimal composition (Nb 0.75 Ir 0.25 )O 2 :10F with ~75 at.% reduction in noble metal content exhibited comparable OER activity to commercial hydrated IrO 2 and nanostructured in-house chemically synthesized IrO 2 . The (Nb,Ir)O 2 :10F electro-catalyst demonstrated excellent long term structural/corrosion stability comparable to in-house chemically synthesized pure IrO 2 :10F. First-principles calculations of the total energies, electronic structures and cohesive energies of the model systems have been performed and correlated to the excellent activity, long term stability of (Nb,Ir)O 2 :F for OER obtained experimentally.

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Nanostructured (Ir,Sn)O2:F – Oxygen Evolution Reaction Anode Electro-Catalyst Powders for PEM Based Water Electrolysis

Journal of The Electrochemical Society, 2014

ABSTRACT Nanostructured powder catalysts comprising solid solutions of F doped SnO2 and IrO2 of d... more ABSTRACT Nanostructured powder catalysts comprising solid solutions of F doped SnO2 and IrO2 of different compositions were synthesized by a simple two step approach. High surface area SnO2:F was prepared initially using CTAB as a surfactant. (Ir,Sn)O-2:F was then synthesized by forming a solid state solution with IrCl4 and SnO2:F followed by heat-treatment in air at 400 degrees C. The catalyst was then coated onto a porous Ti foil and has been studied as a promising anode electro-catalyst for oxygen evolution reaction (OER) in PEM based water electrolysis. The optimal composition of (Ir0.3Sn0.7)O-2:10 wt% F displayed electrochemical activity comparable to the commercially available pure IrO2 demonstrating similar to 70 mol% reduction in noble metal content. The electrochemical stability tests also showed that (Ir,Sn)O-2:F solid solution exhibits much better durability compared to commercial IrO2, the standard (OER) catalyst.

WO3 based solid solution oxide – promising proton exchange membrane fuel cell anode electro-catalyst

Journal of materials chemistry. A, Materials for energy and sustainability, 2015

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Computational and experimental investigation of Co and S-doped Ni2P as an efficient electrocatalyst for acid mediated proton exchange membrane hydrogen evolution reaction

Catalysis Science & Technology, 2021

DFT study illuminating modification of the electronic structure and corresponding experimental va... more

Doped Lithium Orthosilicates - Promising High Rate Lithium-Ion Conductors for Li-S Batteries

Meeting abstracts, 2016

High Performance and Durable (Zn1-xCox)O:N Nanowires As Photoanode for Efficient Hydrogen Production Via Photoelectrochemical Water Splitting

Meeting abstracts, 2015

The rapid depletion of fossil fuels and increasing strain on the environment due to excess consum... more The rapid depletion of fossil fuels and increasing strain on the environment due to excess consumption of the fossil fuels has necessitated the exploration of new renewable energy sources to solve the global energy crisis.1 Hydrogen has been considered as the future promising energy source, capable of providing clean and reliable energy supply and thus, meeting the global energy demand. However, economic production of hydrogen still remains a challenge, limiting its commercialization as a fuel. Hence, the efficient and economic production of hydrogen using renewable energy sources, such as solar, wind, etc. has received special interest, in the aim of finding clean (low carbon footprint) fuel, that will have minimum impact on the environment. Among all promising renewable energy sources such as solar, geothermal, wind, solar derived energy remains a highly attractive approach since it is a de-concentrated and inexhaustible energy source. Hence, solar energy driven water splitting, also known as photo-electrochemical (PEC) water splitting is considered as a promising approach for economic and efficient hydrogen production, since water splitting does not involve any greenhouse gas emission or any toxic byproducts. In PEC water splitting, a semiconductor is used as photoanode, which absorbs solar energy and thus, provides, photogenerated carriers (electrons and holes) for hydrogen evolution reaction (HER) and water oxidation or oxygen evolution reaction (OER), respectively. The development of semiconductor material with low band gap (1.23 eV &amp;amp;lt; Eg &amp;amp;lt; 3 eV) to absorb visible light and thus, drive the HER and OER reactions with minimum over-potential, and minimum density of lattice defects is of considerable interest. This will also facilitate recombination of photo-generated carriers and thus, lower the PEC response, high electrical conductivity and high stability in aqueous electrolyte solution leading to efficient utilization of solar energy, resulting in efficient and economic hydrogen production. Thus far, well studied semiconductor materials such as TiO2, ZnO, Fe2O3 have issues such as wide band gap and poor stability for long term PEC water splitting operation. However, among all these materials, ZnO is a promising material due to its higher electron mobility than TiO2 (~155 cm2 V-1 s-1 for ZnO vs. ~10-5 cm2 V-1 s-1 for TiO2). The systematic band gap engineering of ZnO will help in lowering the band gap of ZnO (3.2 eV), which will improve light absorption in the visible region of interest and number of carriers available for the reaction. In this study, vertically aligned ZnO nanowires (NWs) co-doped with Co and N are explored as photoanode (semiconductor) for PEC water splitting for the first time. These NWs are synthesized using well-known hydrothermal route, followed by heat treatment in NH3 at 400oC, 500oC 600oC and 700oC. These compositions are denoted as (Zn0.95Co0.05)O:N-y (y=400, 500, 600) NWs, where y is the temperature of heat treatment in NH3 atmosphere. The cross-sectional SEM image of (Zn0.95Co0.05)O:N-600 NWs is shown in Fig. 1. The photoelectrochemical characterization of (Zn0.95Co0.05)O:N-y has been carried out in 0.5 M Na2SO4 as an electrolyte, Pt wire as counter electrode and Ag/AgCl as the reference electrode (+0.197 V vs. NHE), using a scan rate of 10 mV/sec and temperature of 260C in H-type cell, where photoanode and cathode (Pt/C) are separated by Nafion membrane (Dupont). Thus, this study explores (Zn1-xCox)O:N NWs as potential semiconductor material for economic and efficient production of hydrogen via PEC water splitting. The results of the synthesis, microstructural and photoelectrochemical activity of these semiconductor materials will be presented and discussed. References: 1. J. R. Miller, Science, 2012, 335, 1312-1313. Acknowledgement: The authors gratefully acknowledge the financial support of NSF grant (CBET-0933141). The authors also acknowledge the Edward R. Weidlein Chair Professorship funds and the Center for Complex Engineered Multifunctional Materials for partial support of this research. Figure 1

F Doped (Ir,Sn,Nb)O2 oxygen Evolution Reaction Electro-Catalysts for PEM Water Electrolysis

Meeting abstracts, 2014

Doped Transition Metal Nitride Supercapacitors (DTMSCs): Mechanisms of Charge Storage

Meeting abstracts, 2014

Charge storage behavior in nitride nanomaterials depends on a number of particle properties and a... more Charge storage behavior in nitride nanomaterials depends on a number of particle properties and also on the nature of the electrode (1-9). Vanadium nitride is a promising supercapacitor material on account of pseudocapacitance arising from the surface oxide/oxynitride phase interactions. We have previously reported excellent charge storage behavior of nanoparticulate vanadium nitride on account of the surface reactions occurring on the surface of the oxide exo-shell. Vanadium oxide is a superior pseudocapacitor material but suffers from poor electronic conductivity(10). Forming a thin surface oxide layer on nanoparticle nitrides yields the benefits of the charge storage along with charge storage occurring in the nitride core itself. However, there is evidence showing that the surface oxide suffers from instability in highly alkaline solutions on account of side-reactions. In addition, the core nitride itself becomes a poor conductor when prepared as fine nanoparticles (&amp;amp;lt;10 nm)(3). In this study, we tailor nitride nanoparticles to engineer architectures similar to that shown in Figure 1by the use of suitable dopants. By using wet chemical procedures, we generate a number of doped nitrides with doped surface oxide structure. We use ab-initio first principle studies to guide our dopant selection with improved electronic conductivity of surface oxide/core nitride and stability of surface oxide being parameters driving our dopant selection. We demonstrate in this study doped VN with superior electronic conductivity, high capacity and long cycle life. In-depth surface characterization using XPS and electrochemical impedance spectroscopy (EIS) to probe change in charge-storage mechanisms are conducted herein to obtain fundamental understanding into the nature of the various doped nitride materials. Change in nanoparticle morphology and surface composition are also examined and related to charge storage behavior. Results of these studies will be presented and discussed. References 1. D. Choi, G. E. Blomgren and P. N. Kumta, Advanced Materials, 18, 1178 (2006). 2. P. Jampani, A. Manivannan and P. N. Kumta, The Electrochemical Society Interface, 19, 57 (2010). 3. P. J. Hanumantha, M. K. Datta, K. S. Kadakia, D. H. Hong, S. J. Chung, M. C. Tam, J. A. Poston, A. Manivannan and P. N. Kumta, Journal of The Electrochemical Society, 160, A2195 (2013). 4. D. Choi, Synthesis, Structure and Electrochemical Characterization of Transition Metal Nitride Supercapacitors Derived by a Two-Step Metal Halide Approach, in Materials Science and Engineering, Carnegie Mellon University, Pittsburgh (2005). 5. D. Choi, G. E. Blomgren and P. N. Kumta, Advanced Materials, 18, 1178 (2006). 6. D. Choi and P. N. Kumta, Journal of the Electrochemical Society, 153, A2298 (2006). 7. D. Choi and P. N. Kumta, Journal of the American Ceramic Society, 90, 3113 (2007). 8. D. Choi and P. N. Kumta, Journal of the American Ceramic Society, 94, 2371 (2011). 9. D. W. Choi and P. N. Kumta, Electrochemical and Solid State Letters, 8, A418 (2005). 10. P. H. Jampani, K. Kadakia, D. H. Hong, R. Epur, J. A. Poston, A. Manivannan and P. N. Kumta, Journal of The Electrochemical Society, 160, A1118 (2013).

Novel Heterostructures for Lithium-Sulfur Batteries

Meeting abstracts, 2014

Effect of Coating and Particle Properties on the Cycling Stability of Li-Ion Conductor (LIC) Coated Sulfur Cathodes

Meeting abstracts, 2015

Amorphous Calcium Phosphate Blended Polymer Coatings for Biomedical Implants

The osseointegration of biomedical implants within the host site is a key aspect to early recover... more The osseointegration of biomedical implants within the host site is a key aspect to early recovery of patients. In this research report we studied the feasibility of depositing polymeric coatings embedded with a novel amorphous calcium phosphate (ACP) formulation using the direct-write inkjet method. Biodegradable polymers that include polycaprolactone (PCL) and poly (lactic-co-glycolic) acid (PLGA) were blended with varying loading concentrations of a proprietary ACP. The direct-write inkjet method was used to deposit 10 and 20 layers of respective materials on polished titanium (Ti) substrates. Surface morphology and chemical composition of the coatings were characterized by optical microscopy and Fourier transform infrared spectroscopy (FTIR), respectively. PCL-ACP composite films showed homogeneous deposition, whereas the PLGA-ACP coatings showed regions coated with bare PLGA polymer without the presence of ACP. The Alamar blue assay was employed to assess the metabolic activity (viability) of the MC3T3 osteoblast precursor cells. Further, an in-vitro live-dead assessment using MC3T3 cells was conducted for cyto-compatibility. This research lays a foundation for developing calcium phosphate containing polymeric composite coatings for orthopedic applications.

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A CALPHAD study on the thermodynamic stability of calcium-, zinc-, and yttrium-doped magnesium in aqueous environments

Materials Science And Engineering: B, Dec 1, 2011

Magnesium has attracted the attention of the biomaterials community as a potential biodegradable ... more Magnesium has attracted the attention of the biomaterials community as a potential biodegradable metallic candidate for use in stents and orthopedic applications. Alloying of Mg with metals such as Ca, Y and Zn, etc., to form alloy precursors is important to optimize its corrosion rate in electrolytic and aqueous environments to understand the alloy response in body fluid environments. In

Alginate encapsulation of chitosan nanoparticles: a viable alternative to soluble chemical signaling in definitive endoderm induction of human embryonic stem cells

Journal of Materials Chemistry B, 2016

Chitoson nanoparticle augmented encapsulated alginate (CNPEA) induces definitive endoderm (DE) di... more

Ab-initio study of fluorine-doped tin dioxide: A prospective catalyst support for water electrolysis

Physica B-condensed Matter, Feb 1, 2011

... 2 Keywords: electronic structure, density functional theory, fluorine doped tin dioxide, dopi... more

Bioactive Synthetic Polymer-Based Polyelectrolyte LbL Coating Assembly on Surface Treated AZ31-Mg Alloys

Journal of Functional Biomaterials, Jan 29, 2023

Polyelectrolyte layer-by-layer (LbL) films on pretreated Mg containing 3 wt.% Al and 1 wt.% Zn (M... more Polyelectrolyte layer-by-layer (LbL) films on pretreated Mg containing 3 wt.% Al and 1 wt.% Zn (MgAZ31) alloy surfaces were prepared under physiological conditions offering improved bioresponse and corrosive protection. Pretreatments of the model MgAZ31 substrate surfaces were performed by alkaline and fluoride coating methods. The anti-corrosion and cytocompatibility behavior of pretreated substrates were evaluated. The LbL film assembly consisted of an initial layer of polyethyleneimine (PEI), followed by alternate layers of poly (lactic-co-glycolic acid) (PLGA) and poly (allylamine hydrochloride) (PAH), which self-arrange via electrostatic interactions on the pretreated MgAZ31 alloy substrate surface. The physicochemical characterization, surface morphologies, and microstructures of the LbL films were investigated using Fourier-transformed infrared spectroscopy (FTIR), atomic force microscopy (AFM), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The in vitro stability studies related to the LbL coatings confirmed that the surface treatments are imperative to achieve the lasting stability of PLGA/PAH layers. Electrochemical impedance spectroscopy measurements demonstrated that pretreated and LbL multilayered coated substrates enhanced the corrosion resistance of the bare MgAZ31 alloy. Cytocompatibility studies using human mesenchymal stem cells seeded directly over the substrates showed that the pretreated and LbLgenerated surfaces were more cytocompatible, displaying reduced cytotoxicity than the bare MgAZ31. The release of bovine serum albumin protein from the LbL films was also studied. The initial data presented cooperatively demonstrate the promise of creating LbL layers on Mg-related bioresorbable scaffolds to obtain improved surface bio-related activity.

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Multi-Element Containing Precious Group Metal-Free Electrocatalysts for Efficient Hydrogen Evolution Reaction in PEM Water Electrolysis

ECS Meeting Abstracts, 2020

Electricity driven proton exchange membrane-based water electrolysis (PEMWE) has demonstrated con... more Electricity driven proton exchange membrane-based water electrolysis (PEMWE) has demonstrated considerable credibility in recent years, establishing high competency enabling PEMWE technology for rapid generation of clean hydrogen fuel 1-7. In order to attain the high efficiency needed and successful commercialization of PEMWE, there is a critical need to identify highly active, robust, and earth-abundant electrocatalysts for accelerating the hydrogen evolution reaction (HER) with minimum energy input 8. In the pursuit of achieving this goal, in the present work, employing the density functional theory (DFT) based calculations for rationalizing the thermodynamics and reaction kinetics of HER, we have investigated the platinum group metal (PGM)-free, earth-abundant, transition metal non-oxide (TMN) based electrocatalysts for acid mediated HER in PEMWE. Based on the theoretical calculations, the as-synthesized TMN electrocatalyst compositions reveal optimized hydrogen adsorption free e...

Engineering Approaches to Dendrite free Lithium Anodes

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