@article {47674, title = {Seed-mediated growth of Pt on high-index faceted Au nanocrystals: the ag lining and implications for electrocatalysis}, journal = {ACS Applied Nano Materials}, volume = {4}, year = {2021}, month = {SEP }, pages = {9155-9166}, type = {Article}, abstract = {Bimetallic Au@Pt nanocrystals (NCs) offer a unique combination of plasmonic and catalytic properties and are a growing field of research. Herein, we report an unusual observation in the behavior of silver ions (Ag+) which was found to play a dominant role in dictating the Pt deposition in a seed-mediated growth method. {\textquoteleft}While the literature is replete with various instances of Ag-assisted Pt deposition whereby higher concentration of Ag+ translates into a thicker Pt shell, in the present study, contradictory observations were made. In the presence of lower amounts of Ag+, thick Pt shells were visualized, while at higher concentrations of Ag+, the extent of Pt deposition via the galvanic replacement reaction was reduced. Additionally, the presence of Ag was deemed necessary for the Pt deposition to take place, either in the form of an underpotential deposition layer on the Au NCs or by introducing Ag+ in the growth solution. We have demonstrated our findings on two different Au NCs enclosed with high-index facets, concave cuboid, and elongated tetrahexahedra, which mirror similar observations and provide generality to our claim. To the best of our knowledge, the time required for Pt deposition on the Au core in the present work is the least among the reported seed-mediated routes. Furthermore, this work, besides presenting a facile and general route for the amalgamation of catalytic and plasmonic properties in hybrid Pt-Au NCs, sheds light on the mechanistic aspects of Ag-assisted wet-chemical generation of bimetallic Au@Pt NCs. The overall electrocatalytic performance of our Au@Pt NCs toward the oxygen reduction reaction was realized to be impressive.}, keywords = {bimetallic nanostructure, galvanic replacement reaction, high-index facet, oxygen reduction reaction, seed-mediated growth, underpotential deposition}, doi = {10.1021/acsanm.1c01714}, author = {Roy, Debashree and Rajendra, Ranguwar and Gangadharan, Pranav K. and Pandikassala, Ajmal and Kurungot, Sreekumar and Ballav, Nirmalya} } @article {47055, title = {Toward pH independent oxygen reduction reaction by polydopamine derived 3D interconnected, iron carbide embedded graphitic carbon}, journal = {ACS Applied Materials \& Interfaces}, volume = {13}, year = {2021}, month = {FEB }, pages = {8147-8158}, type = {Article}, abstract = {

Recent advancements on the development of nonprecious electrocatalysts with iron (Fe) incorporated active centers have generated confidence on realizing cost-effective proton exchange membrane fuel cells (PEMFCs). However, most of these catalysts that emerged as a substitution for the platinum supported on carbon (Pt/C) catalysts in oxygen reduction reaction (ORR) are active under basic conditions, and their feasibility in PEMFCs remains as a challenge. In this scenario, this work reports the synthesis of a Pt-free oxygen reduction electrocatalyst prepared by the annealing of polydopamine grown melamine foam. The prepared catalyst has a three-dimensional (3D) interconnected bilayer network structure possessing the carbon nitride backbone wrapped by graphitic carbon layer bearing iron carbides and nitrides as the active centers (3DFePDC). Interestingly, the 3D-FePDC catalyst displayed an ORR activity both under acidic and basic conditions. Whereas the ORR performance of 3D-FePDC closely matches that of the commercial Pt/C in the basic medium, it displays only a low overpotential value of 60 mV under acidic conditions compared to its Pt counterpart. The kinetics of ORR on 3DFePDC is found to be similar to the four-electron (4e) reduction pathway displayed by Pt/C. Testing of a PEMFC in a single cell mode by using 3D-FePDC as the cathode catalyst and Nafion membrane delivered a maximum power density of 278 mW cm(-2), which is a promising value expected from a system based on the nonprecious metal cathode. Ultimately, as a cost-effective catalyst that can effectively perform irrespective of the pH conditions, 3D-FePDC offers significant prospects in the areas like fuel cells and metal-air batteries which work in acidic and/or basic conditions.

}, keywords = {acidic medium, electrocatalyst, fuel cell, graphitic carbon, Iron carbide, nitrogen doping, nonprecious metal, oxygen reduction reaction}, issn = {1944-8244}, doi = {10.1021/acsami.0c18036}, author = {Gangadharan, Pranav K. and Pandikassala, Ajmal and Kurungot, Sreekumar} } @article {48122, title = {Co-Ni layered double hydroxide for the electrocatalytic oxidation of organic molecules: an approach to lowering the overall cell voltage for the water splitting process}, journal = {ACS Applied Materials \& Interfaces}, volume = {14}, year = {2022}, month = {APR}, pages = {16222-16232}, type = {Article}, abstract = {

Electrocatalytic oxidation of simple organic molecules oilers a promising strategy to combat the sluggish kinetics of the water oxidation reaction (WOR). The low potential requirement, inhibition of the crossover of gases, and formation of value-added products at the anode are benefits of the electrocatalytic oxidation of organic molecules. Herein, we developed cobalt-nickel-based layered double hydroxide (LDH) as a robust material for the electrocatalytic oxidation of alcohols and urea at the anode, replacing the WOR. A facile synthesis protocol to form LDHs with different ratios of Co and Ni is adapted. It demonstrates that the reactants could be efficiently oxidized to concomitant chemical products at the anode. The half-cell study shows an onset potential of 1.30 V for benzyl alcohol oxidation reaction (BAOR), 1.36 V for glycerol oxidation reaction (GOR), 1.33 V for ethanol oxidation reaction (EOR), and 1.32 V for urea oxidation reaction (UOR) compared with 1.53 V for WOR. Notably, the hybrid electrolyzer in a full-cell configuration significantly reduces the overall cell voltage at a 20 mA cm(-2) current density by similar to 15\% while coupling with the BAOR, EOR, and GOR and similar to 12\% with the UOR as the anodic half-cell reaction. Furthermore, the efficiency of hydrogen generation remains unhampered with the types of oxidation reactions (alcohols and urea) occurring at the anode. This work demonstrates the prospects of lowering the overall cell voltage in the case of a water electrolyzer by integrating the hydrogen evolution reaction with suitable organic molecule oxidation.

}, keywords = {electrocatalytic oxidation, energy conversion, imidazole mediated, Layered compounds, water splitting}, issn = {1944-8244}, doi = {10.1021/acsami.2c00982}, author = {Shilpa, Nagaraju and Pandikassala, Ajmal and Krishnaraj, Perayil and Walko, Priyanka S. and Devi, R. Nandini and Kurungot, Sreekumar} } @article {48135, title = {Enhanced proton conductivity in amino acid based self-assembled non-porous hydrogen-bonded organic frameworks}, journal = {Chemical Communications}, volume = {58}, year = {2022}, month = {MAY}, pages = {5972-5975}, type = {Article}, abstract = {

beta-Alaninium oxalate hemihydrate, glycinium oxalate, and L-leucinium oxalate salt-cocrystals as non-porous self-assembled hydrogen-bonded organic frameworks afforded proton conductivity of 2.43 x 10(-2) S cm(-1) (60 degrees C, 95\% RH), 3.03 x 10(-2) S cm(-1) (60 degrees C, 95\% RH), and 1.19 x 10(-2) S cm(-1) (80 degrees C, 95\% RH), respectively. These materials possess an extensive 3-dimensional network of hydrogen bonds in their crystal structures, making them efficient proton conducting membranes. The reduction in conductivity values over 10(-1) S cm(-1) order upon exposure of the samples to a D2O atmosphere in extreme conditions ratified the role of humidity for the conduction of protons. This work explores the relationship between structural features and proton conductivity for the design of proton conducting membranes that are easy to synthesize, eco-friendly, and cheap with potential for futuristic applications.

}, issn = {1359-7345}, doi = {10.1039/d2cc00948j}, author = {Pramanik, Titas and Anand, Ashish and Pandikassala, Ajmal and Illathvalappil, Rajith and Kurungot, Sreekumar and Row, T. N. Guru} } @article {48003, title = {Synthesis of a highly electron-deficient, water-stable, large ionic box: multielectron accumulation and proton conductivity}, journal = {Organic Letters}, volume = {24}, year = {2022}, month = {APR 19}, pages = {3038-3042}, type = {Article}, abstract = {

pi-acidic boxes exhibiting electron reservoir and proton conduction are unprecedented because of their instability in water. We present the synthesis of one of the strongest electron-deficient ionic boxes showing e(-) uptake as well as proton conductivity. Two large anions fit in the box to form anion-pi interactions and form infinite anion-solvent wires. The box with NO3-center dot center dot center dot water wires confers high proton conductivity and presents the first example that manifests redox and ionic functionality in an organic electron-deficient macrocycle.

}, issn = {1523-7060}, doi = {10.1021/acs.orglett.2c00993}, author = {Shukla, Jyoti and Illathvalappil, Rajith and Kumar, Sharvan and Chorol, Sonam and Pandikassala, Ajmal and Kurungot, Sreekumar and Mukhopadhyay, Pritam} } @article {47826, title = {Tuning of oxygen reduction pathways through structural variation in transition metal-doped Ba2In2O5}, journal = {ChemElectroChem}, volume = {9}, year = {2022}, month = {JAN}, pages = {e202101163}, type = {Article}, abstract = {Abstract Oxygen reduction reaction (ORR) can take place either through a two-electron pathway to form H2O2 or through a four-electron pathway to form H2O. Both the reactions are important in the respective fields, viz., H2O2 production as well as fuel cell technology, and rational design of catalysts is mandatory to acquire high energy efficiency in both cases. Here, we report the structure-electrochemical property correlation of a series of perovskite related brownmillerite compounds, Ba2In0.75M0.25O5 (M=Mn/Fe/Co/Ni/Cu), synthesized by solid-state method. On transition metal doping, octahedral distortions were observed, and the highly disordered material tends to follow the 4e transfer mechanism. More symmetrical structures followed the 2e pathway to form H2O2 as the product with high peroxide selectivity. The distortion in the octahedral arrangement can be a descriptor to finetune the selectivity of the catalysts towards the 2e and 4e pathways of ORR.}, keywords = {brownmillerite, Descriptors, Electrochemical H2O2 synthesis, Octahedral distortion, oxygen reduction reaction}, doi = {10.1002/celc.202101163}, author = {Thundiyil, Shibin and Pandikassala, Ajmal and Kurungot, Sreekumar and Devi, R. Nandini} } @article {48200, title = {Unravelling faradaic electrochemical efficiencies over Fe/Co spinel metal oxides using surface spectroscopy and microscopy techniques}, journal = {Nanoscale}, volume = {14}, year = {2022}, month = {NOV }, pages = {15928-15941}, type = {Article}, abstract = {

Cobalt and iron metal-based oxide catalysts play a significant role in energy devices. To unravel some interesting parameters, we have synthesized metal oxides of cobalt and iron (i.e. Fe2O3, Co3O4, Co2FeO4 and CoFe2O4), and measured the effect of the valence band structure, morphology, size and defects in the nanoparticles towards the electrocatalytic hydrogen evolution reaction (HER), the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). The compositional variations in the cobalt and iron precursors significantly alter the particle size from 60 to \<10 nm and simultaneously the shape of the particles (cubic and spherical). The Tauc plot obtained from the solution phase ultraviolet (UV) spectra of the nanoparticles showed band gaps of 2.2, 2.3, 2.5 and 2.8 eV for Fe2O3, Co3O4, Co2FeO4 and CoFe2O4, respectively. Further, the valence band structure and work function analysis using ultraviolet photoelectron spectroscopy (UPS) and core level X-ray photoelectron spectroscopy (XPS) analyses provided better structural insight into metal oxide catalysts. In the Co3O4 system, the valence band structure favors the HER and Fe2O3 favors the OER. The composites Co2FeO4 and CoFe2O4 show a significant change in their core level (O 1s, Co 2p and Fe 2p spectra) and valence band structure. Co3O4 shows an overpotential of 370 mV against 416 mV for Fe2O3 at a current density of 2 mA cm(-2) for the HER. Similarly, Fe2O3 shows an overpotential of 410 mV against the 435 mV for Co3O4 at a current density of 10 mA cm(-2) for the OER. However, for the ORR, Co3O4 shows 70 mV improvement in the half-wave potential against Fe2O3. The composites (Co2FeO4 and CoFe2O4) display better performance compared to their respective parent oxide systems (i.e., Co3O4 and Fe2O3, respectively) in terms of the ORR half-wave potential, which can be attributed to the presence of the oxygen vacancies over the surface in these systems. This was further corroborated in density functional theory (DFT) simulations, wherein the oxygen vacancy formation on the surface of CoFe2O4(001) was calculated to be significantly lower (similar to 50 kJ mol(-1)) compared to Co3O4 (001). The band diagram of the nanoparticles constructed from the various spectroscopic measurements with work function and band gap provides in-depth understanding of the electrocatalytic process.

}, issn = {2040-3364}, doi = {10.1039/d2nr04170g}, author = {Kashyap, Varchaswal and Pandikassala, Ajmal and Singla, Gourav and Khan, Tuhin Suvra and Haider, M. Ali and Vinod, C. P. and Kurungot, Sreekumar} } @article {48324, title = {Pt-anchored-zirconium phosphate nanoplates as high-durable carbon-free oxygen reduction reaction electrocatalyst for PEM fuel cell applications}, journal = {Advanced Sustainable Systems}, volume = {7}, year = {2023}, month = {FEB}, type = {Article}, abstract = {

Commercially available platinum-supported carbon (Pt/C) catalysts are the most widely used oxygen reduction reaction (ORR) electrocatalysts in polymer electrolyte membrane fuel cells (PEMFCs). However, inadequate active triple-phase boundary formation and carbon oxidation in Pt/C during PEMFC operation shorten its lifetime and efficiency. In this direction, a new class of carbon-free electrocatalysts for ORR is prepared by dispersing Pt nanoparticles on ZrP (Zirconium phosphates) nanoplates. In one case (ZrP@Pt), the Pt nanoparticles are found to be closely distributed and completely covering the ZrP nanoplates, whereas in the second case (Pt/ZrP), the Pt nanoparticles selectively restrict dispersion along the edges of the support. ZrP as the support displays an intrinsic proton conductivity of approximate to 0.5 x 10(-4) S cm(-1) at 70 degrees C, with an activation energy (E-a) of 0.19 eV. Pt/ZrP shows better durability after 3000 start-stop cycles. The mass activity of Pt/ZrP is increased by 4.6 times compared to Pt/C, which exhibits a loss in mass activity by 1.37 times. The single-cell level validation of ZrP@Pt, Pt/ZrP, and Pt/C as the electrocatalysts in PEMFC at an operating potential of 0.60 V shows the achievable current densities of 0.600, 0.890, and 0.890 A cm(-2).

}, keywords = {carbon-free electrocatalysts, fuel cells, oxygen reduction reaction, zirconium phosphate}, issn = {2366-7486}, doi = {10.1002/adsu.202200330}, author = {Kumar, Sachin and Yoyakki, Athira and Pandikassala, Ajmal and Soni, Roby and Kurungot, Sreekumar} } @article {48333, title = {Salicylaldehydate coordinated two-dimensional-conjugated metal-organic frameworks}, journal = {Chemical Communications}, volume = {59}, year = {2023}, month = {FEB }, pages = {2608-2611}, type = {Article}, abstract = {

A novel class of copper-based 2D-c-MOF was synthesized from 1,3,5-triformylphloroglucinol using green mechano-chemistry. Herein, metal coordination with the salicylaldehyde functional moiety was explored for the first time in MOFs. Moreover, an intrinsic semiconductive copper-based SA-MOF thin film was fabricated using an in situ salt-free method at room temperature.

}, issn = {1359-7345}, doi = {10.1039/d2cc06283f}, author = {Mohammed, Abdul Khayum and Pena-Sanchez, Pilar and Pandikassala, Ajmal and Gaber, Safa and AlKhoori, Ayesha A. and Skorjanc, Tina and Polychronopoulou, Kyriaki and Kurungot, Sreekumar and Gandara, Felipe and Shetty, Dinesh} } @article {48798, title = {Unlocking the potential of proton conductivity in guanidinium-based ionic covalent organic nanosheets (iCONs) through pore interior functionalization}, journal = {Applied Materials Today}, volume = {33}, year = {2023}, month = {AUG}, pages = {101866}, type = {Article}, abstract = {

Recently, scientists have been exploring the incorporation of proton carriers such as water and phosphoric acid (PA) into the pores and channels of porous materials to enhance proton conduction performance. Ionic covalent organic nanosheets (iCONs) have been identified as promising functional materials due to their inbuilt ionic interfaces, which can facilitate strong interaction with counter ions present inside the pore structure and thus shorten ion transport pathways. However, there is a lack of research related to proton conductivity in iCONs loaded with PA. To address this, we prepared three functionalized guanidinium-based iCONs using a solvothermal condensation reaction between guanidinium amine (TG) and functionalized terephthaldehyde (Da, Dha, and Dma). PA was also incorporated into the iCON structure via ex situ loading to observe its effects on proton conduction performance. The results showed that both the iCONs and PA-iCONs were highly stable in water, organic solvents, acidic and basic media. Amongst these PA-iCONs, one with hydroxyl-functionalization (PA-DhaTG) displayed high proton conductivity at 90 degrees C and 95\% relative humidity due to a Grotthuss mechanism for protons. These functionalized guanidinium-based iCONs could prove useful for applications in energy conversion devices.

}, keywords = {chemical stability, Functionalized pore interior, Guanidinium group, ionic covalent organic nanosheets, proton conductivity}, issn = {2352-9407}, doi = {10.1016/j.apmt.2023.101866}, author = {Kumar, Sushil and Hu, Jiahui and Pandikassala, Ajmal and Kurungot, Sreekumar and Addicoat, Matthew A. and Szekely, Gyorgy} }