Influence of the Nafion agglomerate morphology on the water-uptake behavior and fuel cell performance in the proton exchange membrane fuel cells

Kim, Tae-Hyun,Yoo, Jung Hun,Maiyalagan, T.,Yi, Sung-Chul Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.481 No.-

<P><B>Abstract</B></P> <P>In the preparation of catalyst ink for proton exchange membrane fuel cell, the dispersing solvent has significant influence on the physicochemical and electrochemical properties of catalyst layer (CL), primarily due to the variation of the Nafion ionomer mobility. In this work, based on the Nafion mobility, the effect of solvent on water uptake (WU) behavior in the CL was investigated with respect to different solvents. To vary main- and side-chain mobilities of the Nafion ionomers, we consider different solvents such as glycerol, propylene glycol (PG), isopropyl alcohol (IPA), and <I>N</I>-methyl-2-pyrrolidinone (NMP). Experimental results demonstrated that the NMP CL showed the highest WU at 90% relative humidity, presenting 1.23, 1.27, and 1.28 times higher than that of the glycerol, PG, and IPA CL, respectively. Furthermore, the microstructure and phase images of the CLs revealed that the main-chain mobility governs the clustering behaviors among the Nafion agglomerates, whereas the side-chain mobility determines the ion-clustering behavior within the Nafion agglomerate. From the electrochemical performances, it was observed that the main- and side-chain mobility are related to the electrochemically active area and the proton-conduction pathway, respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Both main- and side-chain mobilities of the Nafion were varied by different solvents. </LI> <LI> The mobilities of both main and side chain affect the catalyst layer morphology. </LI> <LI> The highly phase-separated catalyst layer improved the water-uptake behavior. </LI> <LI> The electrochemical properties were closely related to the Nafion mobilities. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Self-assembled nitrogen-doped graphene quantum dots (N-GQDs) over graphene sheets for superb electro-photocatalytic activity

Riaz, Rabia,Ali, Mumtaz,Sahito, Iftikhar Ali,Arbab, Alvira Ayoub,Maiyalagan, T.,Anjum, Aima Sameen,Ko, Min Jae,Jeong, Sung Hoon Elsevier BV * North-Holland 2019 Applied Surface Science Vol.480 No.-

<P><B>Abstract</B></P> <P>Nitrogen-doped graphene quantum dots (N-GQDs) are emerging electroactive and visible light active organic photocatalysts, known for their high stability, catalytic activity and biocompatibility. The edge surfaces of N-GQDs are highly active, however, when N-GQDs make the film the edges are not fully exposed for catalysis. To avoid this issue, the N-GQDs are shaped to branched leaf shape, with an extended network of voids, offering highly active surfaces (edge) exposed for electrocatalytic and photocatalytic activity. The nitrogen doping causes a decrease in the bandgap of N-GQDs, thus enabling them to be superb visible light photocatalyst, for degradation of Methylene blue dye from water. Photoluminescence results confirmed that by a synergistic combination of the highly conductive substrate; Carbon fabric coated graphene sheets (CF-rGO) the recombination of photogenerated excitons is significantly suppressed, hence enabling their efficient utilization for catalysis. Comparatively, uniformly coated N-GQDs showed 49.3% lower photocatalytic activity, owing to their hidden active sites. The degradation was further boosted by 30% by combining the electrocatalytic activity, i.e. electro-photocatalysis of the proposed electrode. The proposed electrode material was analyzed using TEM, FE-SEM, FTIR, AFM, and WA-XRD, whereas the stability of electrode was confirmed by TGA, tensile test, bending test, and in harsh chemical environments. The proposed photo-electrocatalyst electrode is binder-free, stable, flexible and highly conductive, which makes the electrode quite suitable for flexible catalytic devices like flexible solar cells and wearable supercapacitors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A flexible electrode is fabricated using self-assembled overlayer of Nitrogen doped Graphene Quantum Dots (N-GQDs). </LI> <LI> Self-assembeled highly porous leaflets structure has maximum exposed edge surfaces to accelarate the catalytic reaction. </LI> <LI> The proposed electrode is metal free and is stable at high temperature, harsh chemical environments, and mechanical stresses. </LI> <LI> The surface resistance of the all carbon electrode is only 2.5 Ω sq.<SUP>−1</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Nitrogen doped graphene quantum dots (N-GQDs) were self-assembled (with high porosity) on reduced graphene oxide coated carbon fabric to fabricate a highly stable visible light photocatlytically and electrocatalytically active flexible electrode for water treatment.</P> <P>[DISPLAY OMISSION]</P>

Electrochemical performances of LiNi_1−xMn_xPO₄ (x = 0.05–0.2) olivine cathode materials for high voltage rechargeable lithium ion batteries

Karthikprabhu, S.,Karuppasamy, K.,Vikraman, Dhanasekaran,Prasanna, K.,Maiyalagan, T.,Nichelson, A.,Kathalingam, A.,Kim, Hyun-Seok Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.449 No.-

<P><B>Abstract</B></P> <P>This study demonstrated to synthesis of carbon-free lithium nickel phosphate (LiNiPO<SUB>4</SUB>) and its analogue of manganese doped LiNi<SUB>1−x</SUB>Mn<SUB>x</SUB>PO<SUB>4</SUB> (x = 0.05–0.2) cathode materials by a facile polyol method and their suitability for use in high voltage lithium ion batteries (LIBs). The physicochemical properties were analyzed using X-ray diffraction, Fourier transform infra-red, Raman, field emission scanning electron microscopy (FE-SEM), energy dispersive analysis by X-ray (EDX), and electrochemical studies. FE-SEM showed that the spherical shape particles were uniformly distributed on the surface and EDX confirmed the presence of all the elements in the LiNi<SUB>1−x</SUB>Mn<SUB>x</SUB>PO<SUB>4</SUB> nanostructure. Substitution of Mn dopants with LiNiPO<SUB>4</SUB> significantly improved the electrical and electrochemical performances for LiNi<SUB>1−x</SUB>Mn<SUB>x</SUB>PO<SUB>4</SUB> (x = 0.05–0.2) cathodes. The highly conducting LiNi<SUB>1−x</SUB>Mn<SUB>x</SUB>PO<SUB>4</SUB> (x = 0.1) cathode exhibited initial discharge capacity of 94.2 mA h g<SUP>−1</SUP> at <I>C</I>/4 rate, and 62% capacity retention after 100 cycles between 2.8 and 5.6 V. These features promote LiNi<SUB>1−x</SUB>Mn<SUB>x</SUB>PO<SUB>4</SUB> as a suitable cathode material for high voltage LIBs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Carbon free, LiNiPO<SUB>4</SUB> and Mn doped LiNiPO<SUB>4</SUB> were prepared by a polyol process. </LI> <LI> The Mn doped LiNiPO<SUB>4</SUB> shows the improved electrical performances. </LI> <LI> The CV polarization curve was ascertained in the voltage range of 2.8–5.6 V. </LI> <LI> The cell delivers a maximum discharge capacity of 94.2 mA h g<SUP>−1</SUP> at 0.1 C rate. </LI> </UL> </P>

Recent advances in 2-D nanostructured metal nitrides, carbides, and phosphides electrodes for electrochemical supercapacitors – A brief review

Theerthagiri, Jayaraman,Durai, Govindarajan,Karuppasamy, K.,Arunachalam, Prabhakarn,Elakkiya, Venugopal,Kuppusami, Parasuraman,Maiyalagan, Thandavarayan,Kim, Hyun-Seok THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2018 JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY -S Vol.67 No.-

<P><B>Abstract</B></P> <P>Supercapacitors (SCs) has gained an impressive concentration by the researchers due to its advantages such as high energy and power densities, long cyclic life, rapid charge–discharge rates, low maintenance and desirable safety. Hence it has been widely utilized in energy storage and conversion devices. Among the different components of SC, electrodes play a vital role in the performances of SCs. In this review, we present the recent advances in 2-D nanostructured metal nitrides, carbides, and phosphides based materials for SC electrodes. Finally, the electrochemical stability and designing approach for the future advancement of the electrode materials are also highlighted.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Metal-organic framework derived NiMo polyhedron as an efficient hydrogen evolution reaction electrocatalyst

Karuppasamy, K.,Jothi, Vasanth Rajendiran,Vikraman, Dhanasekaran,Prasanna, K.,Maiyalagan, T.,Sang, Byoung-In,Yi, Sung-Chul,Kim, Hyun-Seok Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.478 No.-

<P><B>Abstract</B></P> <P>Exploring efficient electrocatalyst for H<SUB>2</SUB> evolution reaction (HER) and replacing the noble metal-based catalysts with inexpensive non-noble metal-based HER catalyst is of great importance for the practicality of hydrogen powered clean technologies. Here, we explore a new class of metal organic framework (MOF) composite (NiMo polyhedron) as an active electrocatalyst material for HER application - synthesized through the conventional hydrothermal process. The bimetallic MOF system having grown on Nickel foam (NiMo/NiMoO<SUB>4</SUB>@NC/NF) delivers higher catalytic activity by achieving a current density of 10 mA cm<SUP>−2</SUP> at a low overpotential of 80 mV, with a Tafel slope of 98.9 mV dec<SUP>−1</SUP> (0.5 M H<SUB>2</SUB>SO<SUB>4</SUB>), comparing favorably with the electrochemical enactment of existing bimetallic MOF-based catalysts. The enhanced HER activity of the synthesized MOF, is primarily due to the structural merits of MOF and the synergy between the MOF and the guest species (Ni and Mo metal atoms). Adding to the excellent HER performance, the electrode also exhibits good stability in acidic medium for a prolonged duration of 24 h. Hence, the synthesized low-cost, non-Pt electrode MOFs with its greater HER performance can be an auspicious applicant as an HER catalyst for water splitting and hydrogen generation applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Noble, Pt free alternate electrocatalysts for HER were identified. </LI> <LI> Ni, Mo based bimetallic MOFs were prepared by hydrothermal process. </LI> <LI> The synthesized NiMO-MOFs possessed polyhedron morphology. </LI> <LI> It achieved a current density of 10 mA cm<SUP>−2</SUP> at a low overpotential of 98.9 mV. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Recent advances in 2-D nanostructured metal nitrides, carbides, and phosphides electrodes for electrochemical supercapacitors – A brief review

Jayaraman Theerthagiri,Govindarajan Durai,K. Karuppasamy,Prabhakarn Arunachalam,Venugopal Elakkiya,Parasuraman Kuppusami,Thandavarayan Maiyalagan,김현석 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.67 No.-

Supercapacitors (SCs) has gained an impressive concentration by the researchers due to its advantages such as high energy and power densities, long cyclic life, rapid charge–discharge rates, low maintenance and desirable safety. Hence it has been widely utilized in energy storage and conversion devices. Among the different components of SC, electrodes play a vital role in the performances of SCs. In this review, we present the recent advances in 2-D nanostructured metal nitrides, carbides, and phosphides based materials for SC electrodes. Finally, the electrochemical stability and designing approach for the future advancement of the electrode materials are also highlighted.