Guruprakash Karkera
@hiu-batteries.de/en
Post-doctoral fellow
Helmholtz Institute Ulm
RESEARCH INTERESTS
Energy storage devices; electrocatalysis, materials for green energy
Scopus Publications
Scopus Publications
Ling Lin, Ziming Ding, Guruprakash Karkera, Thomas Diemant, Mohana V. Kante, Daisy Agrawal, Horst Hahn, Jasmin Aghassi‐Hagmann, Maximilian Fichtner, Ben Breitung,et al.
Wiley
With respect to efficient use of diminishing or harder to reach energy resources, the catalysis of processes that will otherwise require high overpotentials is a very important application in today's world. As a newly developed class of materials, high‐entropy sulfides (HESs) are promising electrocatalysts for a variety of different reactions. In this report, HESs containing five or six transition metals are synthesized in a one‐step mechanochemical process. Seven HESs of Pnma (M:S≈1:1) and three Pa‐3 (M:S = 1:2) structures are investigated as electrocatalysts for the oxygen evolution reaction (OER). The performances and properties of the HESs with different compositions and structures are compared with each other and with commercial IrO2 as reference material, in terms of OER overpotential, Tafel slope, electrochemically active surface area, ionic conductivity, and durability. The structural and chemical properties of these HESs are determined by X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, X‐ray photoelectron spectroscopy, and energy‐dispersive X‐ray spectroscopy. Most of the HESs show excellent and promising performance as OER electrocatalysts under alkaline conditions, and outperform the reference OER catalyst IrO2.
Guruprakash Karkera, Mervyn Soans, Ayça Akbaş, Raiker Witter, Holger Euchner, Thomas Diemant, Musa Ali Cambaz, Zhen Meng, Bosubabu Dasari, Shivaraju Guddehalli Chandrappa,et al.
Wiley
Tobias Braun, Sirshendu Dinda, Guruprakash Karkera, Georgian Melinte, Thomas Diemant, Christian Kübel, Maximilian Fichtner, and Frank Pammer
Wiley
AbstractThe development of commercially viable fuel cells and metal‐air batteries requires effective and cheap bifunctional catalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Multi‐component Pt−Fe−Co−Ni nanoparticles on multi‐walled carbon nanotubes (MWCNTs) were synthesized by wet chemistry route via NaBH4 reduction of metal salts, followed by sintering at different temperatures. The catalyst demonstrates an excellent ORR activity and a promising OER activity in 0.1 m KOH, with a bi‐functional over‐potential, ΔE of 0.83 V, which is comparable to the values of Pt/C or RuO2. Furthermore, it shows outstanding long‐term stability in ORR and OER, namely diffusion limited current density at a potential of 0.3 V decreased just by 5.5 % after 10000 cycles in ORR. The results of the PFCN@NT300 indicate a significant effect of the substitution of Pt by the transition metal (TM) and the formation of nanoparticles on the catalytic performance, especially in the OER.
Ediga Umeshbabu, Divya Velpula, Guruprakash Karkera, Maddukuri Satyanarayana, Vasudevarao Pasala, and P. Justin
MDPI AG
Herein, we describe the synthesis and evaluation of hierarchical mesoporous orthorhombic niobium oxide (T-Nb2O5) as an anode material for rechargeable lithium-ion batteries (LIB). The as-synthesized material addresses key challenges such as beneficial porous structure, poor rate capability, and cycling performance of the anode for Li-ion devices. The physicochemical characterization results reveal hierarchical porous nanostructure morphology with agglomerated particles and a 20 to 25 nm dimension range. Moreover, the sample has a high specific surface area (~65 m2 g−1) and pore volume (0.135 cm3 g−1). As for the application in Li-ion devices, the T-Nb2O5 delivered an initial discharging capacity as high as 225 mAh g−1 at 0.1 A g−1 and higher rate capability as well as remarkable cycling features (~70% capacity retention after 300 cycles at 250 mA g−1) with 98% average Coulombic efficiency (CE). Furthermore, the scan rate-dependent charge storage mechanism of the T-Nb2O5 electrode material was described, and the findings demonstrate that the electrode shows an evident and highly effective pseudocapacitive Li intercalation behaviour, which is crucial for understanding the electrode process kinetics. The origin of the improved performance of T-Nb2O5 results from the high surface area and mesoporous structure of the nanoparticles.
Shivaraju Guddehalli Chandrappa, Guruprakash Karkera, Vasantha A. Gangadharappa, Dehong Chen, Rachel A. Caruso, and Prakash Annigere S.
American Chemical Society (ACS)
Zhen Meng, Adam Reupert, Yushu Tang, Zhenyou Li, Guruprakash Karkera, Liping Wang, Ananyo Roy, Thomas Diemant, Maximilian Fichtner, and Zhirong Zhao-Karger
American Chemical Society (ACS)
Calcium (Ca) batteries represent an attractive option for electrochemical energy storage due to physicochemical and economic reasons. The standard reduction potential of Ca (-2.87 V) is close to Li and promises a wide voltage window for Ca full batteries, while the high abundance of Ca in the earth's crust implicates low material costs. However, the development of Ca batteries is currently hindered by technical issues such as the lack of compatible electrolytes for reversible Ca2+ plating/stripping and high-capacity cathodes with fast kinetics. Herein, we employed FeS2 as a conversion cathode material and combined it with a Li+/Ca2+ hybrid electrolyte for Ca batteries. We demonstrate that Li+ ions ensured reversible Ca2+ plating/stripping on the Ca metal anode with a small overpotential. At the same time, they enable the conversion of FeS2, offering high discharge capacity. As a result, the Ca/FeS2 cell demonstrated an excellent long-term cycling performance with a high discharge capacity of 303 mAh g-1 over 200 cycles. Even though the practical application of such an approach is questionable due to the high quantity of electrolytes, we believe that our scientific findings still provide new directions for studying Ca batteries with long-term cycling.
Simon Schweidler, Yushu Tang, Ling Lin, Guruprakash Karkera, Alaa Alsawaf, Lucile Bernadet, Ben Breitung, Horst Hahn, Maximilian Fichtner, Albert Tarancón,et al.
Frontiers Media SA
High-entropy materials offer a wide range of possibilities for synthesizing new functional ceramics for different applications. Many synthesis methods have been explored to achieve a single-phase structure incorporating several different elements, yet a comparison between the synthesis methods is crucial to identify the new dimension such complex ceramics bring to material properties. As known for ceramic materials, the synthesis procedure usually has a significant influence on powder morphology, elemental distribution, particle size and powder processability. Properties that need to be tailored according to specific applications. Therefore, in this study perovskite-type high-entropy materials (Gd0.2La0.2–xSrxNd0.2Sm0.2Y0.2) (Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)O3 (x = 0 and x = 0.2) are synthesized for the first time using mechanochemical synthesis and a modified Pechini method. The comparison of different syntheses allows, not only tailoring of the constituent elements of high-entropy materials, but also to optimize the synthesis method as needed to overcome limitations of conventional ceramics. To exploit the novel materials for a variety of energy applications, their catalytic activity for oxygen evolution reaction was characterized. This paves the way for their integration into, e.g., regenerative fuel cells and metal air batteries.
Junbo Wang, Sören L Dreyer, Kai Wang, Ziming Ding, Thomas Diemant, Guruprakash Karkera, Yanjiao Ma, Abhishek Sarkar, Bei Zhou, Mikhail V Gorbunov,et al.
IOP Publishing
Abstract P2-type layered oxides with the general Na-deficient composition Na x TMO2 (x < 1, TM: transition metal) are a promising class of cathode materials for sodium-ion batteries. The open Na+ transport pathways present in the structure lead to low diffusion barriers and enable high charge/discharge rates. However, a phase transition from P2 to O2 structure occurring above 4.2 V and metal dissolution at low potentials upon discharge results in rapid capacity degradation. In this work, we demonstrate the positive effect of configurational entropy on the stability of the crystal structure during battery operation. Three different compositions of layered P2-type oxides were synthesized by solid-state chemistry, Na0.67(Mn0.55Ni0.21Co0.24)O2, Na0.67(Mn0.45Ni0.18Co0.24Ti0.1Mg0.03)O2 and Na0.67(Mn0.45Ni0.18Co0.18Ti0.1Mg0.03Al0.04Fe0.02)O2 with low, medium and high configurational entropy, respectively. The high-entropy cathode material shows lower structural transformation and Mn dissolution upon cycling in a wide voltage range from 1.5 to 4.6 V. Advanced operando techniques and post-mortem analysis were used to probe the underlying reaction mechanism thoroughly. Overall, the high-entropy strategy is a promising route for improving the electrochemical performance of P2 layered oxide cathodes for advanced sodium-ion battery applications.
Guruprakash Karkera, Mervyn Soans, Bosubabu Dasari, Ediga Umeshbabu, Musa Ali Cambaz, Zhen Meng, Thomas Diemant, and Maximilian Fichtner
Wiley
Ediga Umeshbabu, M. Satyanarayana, Guruprakash Karkera, Ashok Pullamsetty, and P. Justin
Royal Society of Chemistry (RSC)
A simple, inexpensive and eco-friendly approach is developed toward the synthesis of large-scale production of α-MnO2 nanowires by quick redox-reaction between permanganate and glycine, and are investigated as anode material for Li-ion batteries.
Ling Lin, Kai Wang, Abhishek Sarkar, Christian Njel, Guruprakash Karkera, Qingsong Wang, Raheleh Azmi, Maximilian Fichtner, Horst Hahn, Simon Schweidler,et al.
Wiley
High‐entropy sulfides (HESs) containing 5 equiatomic transition metals (M), with different M:S ratios, are prepared by a facile one‐step mechanochemical approach. Two new types of single‐phase HESs with pyrite (Pa‐3) and orthorhombic (Pnma) structures are obtained and demonstrate a homogeneously mixed solid solution. The straightforward synthesis method can easily tune the desired metal to sulfur ratio for HESs with different stoichiometries, by utilizing the respective metal sulfides, even pure metals, and sulfur as precursor chemicals. The structural details and solid solution nature of HESs are studied by X‐ray diffraction, transmission electron microscopy, energy‐dispersive X‐ray spectroscopy, electron energy loss spectroscopy, X‐ray photoelectron spectroscopy, inductively coupled plasma optical emission spectroscopy, and Mössbauer spectroscopy. Since transition metal sulfides are a very versatile material class, here the application of HESs is presented as electrode materials for reversible electrochemical energy storage, in which the HESs show high specific capacities and excellent rate capabilities in secondary Li‐ion batteries.
Shivaraju Guddehalli Chandrappa, Prabu Moni, Dehong Chen, Guruprakash Karkera, Kunkanadu R. Prakasha, Rachel A. Caruso, and Annigere S. Prakash
American Chemical Society (ACS)
Dasari Bosubabu, Ramakumar Sampathkumar, Guruprakash Karkera, and Kannadka Ramesha
American Chemical Society (ACS)
The constant search for cost-effective and high-performance materials for Li-ion batteries (LIBs) has increased with time. Here, we synthesized low-cost multi-heteroatom co-doped carbon from biowas...
Guruprakash Karkera, M. Anji Reddy, and Maximilian Fichtner
Elsevier BV
Shivaraju Guddehalli Chandrappa, Prabu Moni, Dehong Chen, Guruprakash Karkera, Kunkanadu R. Prakasha, Rachel A. Caruso, and Annigere S. Prakash
Royal Society of Chemistry (RSC)
The rechargeable zinc–air battery is a clean technology for energy storage applications but is impeded by the slow kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) during its cycling.
Syed Atif Pervez, Bhaghavathi P. Vinayan, Musa Ali Cambaz, Georgian Melinte, Thomas Diemant, Tobias Braun, Guruprakash Karkera, R. Jürgen Behm, and M. Fichtner
Royal Society of Chemistry (RSC)
Formation of nano-sized interphase layers, containing organic and inorganic species, in an interface modified Li–sulfur solid-state battery.
Guruprakash Karkera and Annigere S. Prakash
American Chemical Society (ACS)
In the loop of numerous challenges and ambiguities, Li-O2 batteries are crawling to reach their commercialization phase. To achieve the progressive milestones, along with developments in the architecture of cathode, anode and electrolytes, understanding its failure mode is equally important. Under unrestricted charge-discharge protocol, cycleability of non-aqueous Li-O2 batteries are limited to only few cycles. This report examines an additive-free ether based Li-O2 battery in perspective of identifying the origin of possible side reactions and their affiliations to integral components of the battery. Structural and compositional changes during every charge-discharge sequence are studied using bottom-up sequential tear down analysis. The substantial increase in impedance and corresponding decrease in capacities after every cycle are interrelated to the amount of electrode passivation resulting from the discharge products and electrolyte decomposition. From the tear down analysis, it is approximated that, among the total capacity loss, ≈ 55% is attributed to the cathode, ≈ 28% of the loss corresponds to the anode and ≈ 17 % is attributed to the electrolyte, given that battery failure instigates from the "reactive oxygen species". Electrochemically formed Li2O2 via superoxide pathway induces large decomposition overpotentials up to 4.6 V vs. Li/Li+ due to its overrated reactivity with electrolyte and carbon support. In contrary, efficient decomposition of chemically formed Li2O2 below 3.9 V proves that the extra charge potential observed for electrochemically formed Li2O2 is in fact consumed for the decomposition of irreversibly formed side products via superoxide pathway. Spontaneous reactivity of Li2O2 and trivial reactivity of Li2O highlights the need of advanced strategies to manoeuver oxygen red-ox in selective pathways that unaffect the electrolyte and electrodes, and necessity of their synchronized performance for the evolution of practical Li-O2 batteries.
Shivaraju Guddehalli Chandrappa, Prabu Moni, Guruprakash Karkera, and Annigere S. Prakash
Royal Society of Chemistry (RSC)
MnCo2O4–GS nano composite by a one-pot sonochemical method and its high performance as an active cathode catalyst for a Zn–air battery.
Guruprakash Karkera, Shivaraju Guddehalli Chandrappa, and Annigere S. Prakash
Wiley
With an anticipation of their use in electric vehicles, Li-O2 batteries are found to be attractive despite their complex chemistry and drawbacks. To be successful, cathode materials that are robust enough to overcome the sluggish kinetics of the charge-discharge reactions are essential. This work reports sonochemically synthesized porous MnCo2 O4 /graphene (MCO/G) as a hybrid cathode material in nonaqueous Li-O2 batteries. The MCO/G hybrid is synthesized in less than four hours and offers a strong synergistic coupling between the MnCo2 O4 nanospheres and graphene sheets. It catalyzes the oxygen reduction through a three-electron-transfer process and initiates the oxygen evolution at 1.55 V vs. RHE in basic medium. A small charge-discharge voltage hysteresis of 0.8 V and a cycle life of 250 cycles at a limited capacity of 1000 mAh g-1 in a tetraglyme-based nonaqueous Li-O2 battery is demonstrated. The porous channels created on the sonochemically synthesized cathode facilitates easy oxygen adsorption onto the active sites to accommodate more discharge products following its decomposition. It exhibits a better rate capability in comparison to the widely used Vulcan carbon and benchmark Pt/C catalysts. The excellent cyclability, rate capability, and low overpotential demonstrates MnCo2 O4 /graphene composite as a promising cathode candidate for Li-O2 batteries. The porous nanosphere architecture with internal oxygen diffusion pathways and peripheral conductive graphene extensions fulfils the requirements that a robust cathode is expected to have to overcome the harsh Li-O2 battery conditions and to serve as a high-rate-capable cathode for Li-O2 batteries.
Guruprakash Karkera and A. S. Prakash
American Chemical Society (ACS)
As an alternative to air intolerant nonaqueous electrolytes, a LiNO3–KNO2–CsNO3 (37:39:24) eutectic salt mixture at 140 °C is investigated as a molten electrolyte for Li–O2 batteries. The inorganic eutectic promotes the highly reversible formation–decomposition mechanism of Li2O2, as a robust electrolyte in oxidative conditions. An in situ formed shielding layer composed of Li2O and Li3N keeps the Li anode intact during vigorous cell conditions, providing faster Li-ion diffusion kinetics and stable cycling performance. We report an inorganic electrolyte Li–O2 battery that exhibits the lowest charge–discharge overpotentials of 40 mV and high rate capabilities at 3 mA/cm2 and is cycleable up to 200 times at a restricted capacity of 500 mAh/gcarbon. The performance is achieved on a bare carbon electrode with a round-trip energy efficiency close to 98%. This work emphasizes that the use of an inorganic electrolyte would significantly eliminate the side reactions associated with charge–discharge reactions and ...
Guruprakash Karkera, Tanmay Sarkar, Mridula Dixit Bharadwaj, and Annigere. S. Prakash
Wiley
Solid‐state electrochemistry is drawing considerable interest as the interconversion of O2 and water playing an important role in energy conversion and storage technologies. With the aim of developing an efficient bifunctional catalyst by tuning the electronic properties and local structure around the 3d metal in CoWO4, solid solutions of Co1−xMnxWO4 are investigated. Nanocrystalline Co1−xMnxWO4 (x=0 to 1) phases with a unique exposure of low surface energy planes are synthesized by hydrothermal methods. Replacing an optimum amount of Co with Mn to enhance the catalytic activity leads a observation of a negative shift in the Co2+/3+ redox wave and onset of the oxygen evolution reaction (OER), indicating a strong electronic interaction between the two elements. The composition corresponding to Co0.5Mn0.5WO4 has demonstrated great ability to catalyze both the OER and oxygen reduction reaction (ORR) with a combined overpotential of 0.89 V. It exhibited an OER current density of 10 mA cm−2 at an overpotential of 400 mV. Whereas ORR current density of 3 mA cm−2 is reached at a potential of 0.74 V versus reversible hydrogen electrode (RHE). The density functional theory revealed that the substitution of Mn in CoWO4 elevate the 3d metal d band center closer to the Fermi energy and hence ease the electron transfer to facilitate ORR and OER.