Recent advances in electrocatalysts toward the oxygen reduction reaction: the case of PtNi octahedra

Chaudhari, Nitin K.,Joo, Jinwhan,Kim, Byeongyoon,Ruqia, Bibi,Choi, Sang-Il,Lee, Kwangyeol The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.43

<P>Designing highly efficient and durable electrocatalysts for the oxygen reduction reaction (ORR), the key step for the operation of polymer electrolyte membrane fuel cells (PEMFCs), is of a pivotal importance for advancing PEMFC technology. Since the most significant progress has been made on Pt3Ni(111) alloy surfaces, nanoscale PtNi alloy octahedra enclosed by (111) facets have emerged as promising electrocatalysts toward the ORR. However, because their practical uses have been hampered by the cost, sluggish reaction kinetics, and poor durability, recent advances have engendered a wide variety of structure-, size-, and composition-controlled bimetallic PtNi octahedra. Herein, we therefore review the important recent developments of PtNi octahedral electrocatalysts point by point to give an overview of the most promising strategies. Specifically, the present review article focuses on the synthetic methods for the PtNi octahedra, the core-shell and multi-metallic strategies for performance improvement, and their structure-, size-, and composition-control-based ORR activity. By considering the results achieved in this field, a prospect for this alloy nanocatalysts system for future sustainable energy applications is also proposed.</P>

Pt-Cu based nanocrystals as promising catalysts for various electrocatalytic reactions

Chaudhari, Nitin K.,Hong, Yongju,Kim, Byeongyoon,Choi, Sang-Il,Lee, Kwangyeol The Royal Society of Chemistry 2019 Journal of materials chemistry. A, Materials for e Vol.7 No.29

<P>Taking into account availability and cost, the development of Pt bimetallic alloy nanocatalysts containing earth abundant elements is of vital interest in advancing technologies that depend on electrocatalytic reactions. In this regard, a number of studies on Pt-Cu based alloy nanocrystals have been performed for various electrocatalytic oxidation/reduction reactions owing to their novel physico-chemical properties. Herein, we present an in-depth review on recent developments in Pt-Cu based nanostructures from the viewpoint of electrocatalysts for various reactions. In this review, the synthesis methodologies and composition- and morphology-dependent catalytic properties of Pt-Cu based electrocatalysts are extensively discussed and summarized. The insights into the remaining challenges and the directions for future research on Pt-Cu electrocatalysts are also highlighted for practical applications in renewable energy systems.</P>

Nanodendrites of platinum-group metals for electrocatalytic applications

Chaudhari, Nitin K.,Joo, Jinwhan,Kwon, Hyuk-bu,Kim, Byeongyoon,Kim, Ho Young,Joo, Sang Hoon,Lee, Kwangyeol Springer-Verlag 2018 NANO RESEARCH Vol.11 No.12

N-Carbon from Waste Tea as Efficient Anode Electrode Material in Lithium Ion Batteries

Chaudhari, Nitin K.,Bhattacharjya, Dhrubajyoti,Kim, Hern,Yu, Jong-Sung,Chung, Wook-Jin American Scientific Publishers 2017 Journal of nanoscience and nanotechnology Vol.17 No.3

<P>Nanostructured carbon having nitrogen as heteroatom was synthesized from waste tea, a cheap and abundant waste generated around the world. The synthesis process is simple, environmental being one-step pyrolysis in inert atmosphere. The carbon synthesized at 800 degrees C (WTC-800) has mesh like morphology with abundant mesopores. The BET analysis reveals mesoporous nature with specific surface area of 384 m(2)g(-1). The porous morphology was found to diminish with increase in pyrolysis temperature. XPS analysis reveals the presence of 1.8-2.5% N-content with predominantly graphitic-N. As-synthesized carbons are investigated as anode material for Li-ion battery. The mesoporous structure and N doping endowed WTC-800 with high reversible capacity up to 567 mAhg(-1) at 0.1 C rate, much higher than commercial graphite based anode. Furthermore, the charge discharge process of WTC-800 is not only stable and reversible at high current rate (49% retention at 1 C rate), but also stable up to 100 cycles (78% retention). Relation of capacitive performance with surface area, porosity and N doping is studied and explained promptly. Combined with easy synthesis method, mesoporous structure, inherent N content with abundantly available waste precursor made this carbon material as suitable candidate for electrode materials in Li ion battery applications.</P>

MXene: an emerging two-dimensional material for future energy conversion and storage applications

Chaudhari, Nitin K.,Jin, Hanuel,Kim, Byeongyoon,San Baek, Du,Joo, Sang Hoon,Lee, Kwangyeol Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.47

<P>The development of two-dimensional (2D) high-performance electrode materials is the key to new advances in the fields of energy conversion and storage. MXenes, a new intriguing family of 2D transition metal carbides, nitrides, and carbonitrides, have recently received considerable attention due to their unique combination of properties such as high electrical conductivity, hydrophilic nature, excellent thermal stability, large interlayer spacing, easily tunable structure, and high surface area. In this review, we discuss how 2D MXenes have emerged as efficient and economical nanomaterials for future energy applications. We highlight the promising potential of these materials in energy conversion and storage applications, such as water electrolyzers, lithium ion batteries, and supercapacitors. Finally, we present an outlook of the future development of MXenes for sustainable energy technologies.</P>

Nanostructured materials on 3D nickel foam as electrocatalysts for water splitting

Chaudhari, Nitin K.,Jin, Haneul,Kim, Byeongyoon,Lee, Kwangyeol The Royal Society of Chemistry 2017 Nanoscale Vol.9 No.34

<P>Highly efficient and low-cost electrocatalysts are essential for water spitting<I>via</I>electrolysis in an economically viable fashion. However, the best catalytic performance is found with noble metal-based electrocatalysts, which presents a formidable obstacle for the commercial success of electrolytic water splitting-based H2production due to their relatively high cost and scarcity. Therefore, the development of alternative inexpensive earth-abundant electrode materials with excellent electrocatalytic properties is of great urgency. In general, efficient electrocatalysts must possess several key characteristics such as low overpotential, good electrocatalytic activity, high stability, and low production costs. Direct synthesis of nanostructured catalysts on a conducting substrate may potentially improve the performance of the resultant electrocatalysts because of their high catalytic surface areas and the synergistic effect between the electrocatalyst and the conductive substrate. In this regard, three dimensional (3D) nickel foams have been advantageously utilized as electrode substrates as they offer a large active surface area and a highly conductive continuous porous 3D network. In this review, we discuss the most recent developments in nanostructured materials directly synthesized on 3D nickel foam as potential electrode candidates for electrochemical water electrolysis, namely, the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). We also provide perspectives and outlooks for catalysts grown directly on 3D conducting substrates for future sustainable energy technologies.</P>

Ferric phosphide carbon nanocomposites emerging as highly active electrocatalysts for the hydrogen evolution reaction

Chaudhari, Nitin K.,Yu, Peng,Kim, Byeongyoon,Lee, Kwangyeol,Li, Jinghong The Royal Society of Chemistry 2018 Dalton Transactions Vol.47 No.45

<P>Rational design and synthesis of efficient hydrogen evolution reaction (HER) electrocatalysts from Earth-abundant elements are essential for the development of economical water-splitting processes. This Frontier article will highlight the recent development and advances in designing ferric phosphide (FeP) based electrode materials for the HER.</P>

Evaluation of Toxicity and Gene Expression Changes Triggered by Oxide Nanoparticles

Dua, Pooja,Chaudhari, Kiran N.,Lee, Chang-Han,Chaudhari, Nitin K.,Hong, Sun-Woo,Yu, Jong-Sung,Kim, So-Youn,Lee, Dong-Ki Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.6

Several studies have demonstrated that nanoparticles (NPs) have toxic effects on cultured cell lines, yet there are no clear data describing the overall molecular changes induced by NPs currently in use for human applications. In this study, the in vitro cytotoxicity of three oxide NPs of around 100 nm size, namely, mesoporous silica (MCM-41), iron oxide ($Fe_2O_3$-NPs), and zinc oxide (ZnO-NPs), was evaluated in the human embryonic kidney cell line HEK293. Cell viability assays demonstrated that 100 ${\mu}g/mL$ MCM-41, 100 ${\mu}g/mL$ $Fe_2O_3$, and 12.5 ${\mu}g/mL$ ZnO exhibited 20% reductions in HEK293 cell viability in 24 hrs. DNA microarray analysis was performed on cells treated with these oxide NPs and further validated by real time PCR to understand cytotoxic changes occurring at the molecular level. Microarray analysis of NP-treated cells identified a number of up- and down-regulated genes that were found to be associated with inflammation, stress, and the cell death and defense response. At both the cellular and molecular levels, the toxicity was observed in the following order: ZnO-NPs > $Fe_2O_3$-NPs > MCM-41. In conclusion, our study provides important information regarding the toxicity of these three commonly used oxide NPs, which should be useful in future biomedical applications of these nanoparticles.

Evaluation of Toxicity and Gene Expression Changes Triggered by Oxide Nanoparticles

Pooja Dua,김소연,유종성,홍선우,Nitin K. Chaudhari,Chang Han Lee,chaudhari kiran nanaji,Dong-ki Lee 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.6

Several studies have demonstrated that nanoparticles (NPs) have toxic effects on cultured cell lines, yet there are no clear data describing the overall molecular changes induced by NPs currently in use for human applications. In this study, the in vitro cytotoxicity of three oxide NPs of around 100 nm size, namely,mesoporous silica (MCM-41), iron oxide (Fe_2O_3-NPs), and zinc oxide (ZnO-NPs), was evaluated in the human embryonic kidney cell line HEK293. Cell viability assays demonstrated that 100 μg/mL MCM-41, 100 μg/mL Fe_2O_3, and 12.5 μg/mL ZnO exhibited 20% reductions in HEK293 cell viability in 24 hrs. DNA microarray analysis was performed on cells treated with these oxide NPs and further validated by real time PCR to understand cytotoxic changes occurring at the molecular level. Microarray analysis of NP-treated cells identified a number of up- and down-regulated genes that were found to be associated with inflammation,stress, and the cell death and defense response. At both the cellular and molecular levels, the toxicity was observed in the following order: ZnO-NPs > Fe_2O_3-NPs > MCM-41. In conclusion, our study provides important information regarding the toxicity of these three commonly used oxide NPs, which should be useful in future biomedical applications of these nanoparticles

Lanthanide metal-assisted synthesis of rhombic dodecahedral MNi (M = Ir and Pt) nanoframes toward efficient oxygen evolution catalysis

Jin, Haneul,Hong, Yongju,Yoon, Jisun,Oh, Aram,Chaudhari, Nitin K.,Baik, Hionsuck,Joo, Sang Hoon,Lee, Kwangyeol unknown 2017 Nano energy Vol.42 No.-

<P><B>Abstract</B></P> <P>Mixed metal alloy nanoframeworks have shown a great promise as electrocatalysts in water electrolyzers and fuel cells. Although a limited number of mixed metal alloy nanoframeworks have been synthesized through phase segregation of alloy phases and removal of a component, there remains a strong need for a straightforward and facile synthesis route to this important nanostructure. A wide avenue for nanoframework structures can be opened with a fail-proof method for edge-coating shape-controlled template nanoparticles. Herein, we demonstrate that lanthanide metal chlorides can selectively passivate facets of a Ni nanotemplate, leaving the edges for the growth of a secondary metal (M = Ir, Pt). The edge-deposited metal can be further in situ mixed with the underlying Ni phase to afford rhombic dodecahedral nanoframes of binary alloy phases, namely, IrNi (IrNi-RF) and PtNi (PtNi-RF). IrNi-RF showed excellent electrocatalytic activity for the oxygen evolution reaction (OER) in an acidic electrolyte, requiring and overpotential of only 313.6mV at 10mAcm<SUP>−2</SUP>. Furthermore, even after 5000 potential cycles in the OER, IrNi-RF underwent little performance loss with an overpotential of 329.3mV at 10mAcm<SUP>−2</SUP>, demonstrating excellent catalytic stability. The presence of highly active grain boundaries, agglomeration-free frame structures, as well as the presence of IrNi/IrO<SUB>x</SUB> interface might be responsible for the excellent electrocatalytic activity and stability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Facets of template Ni nanoparticle are passivated by lanthanide metal chlorides to induce selective deposition of Pt or Ir on the edges, resulting in IrNi and PtNi alloy frameworks. </LI> <LI> IrNi nanoframe exhibits a great oxygen evolution reaction (OER) performance in acidic electrolyte and retains five times higher current density than that of Ir/C after 5000 cycles at 1.53 V. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P> <B>Synthesis of MNi (M = Ir or Pt) nanoframe</B> <I> <B>via</B> </I> <B>facet-passivation agents</B> and its excellent electrocatalytic activity and durability to oxygen evolution reaction in acidic electrolyte.</P> <P>[DISPLAY OMISSION]</P>