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Kuttiyiel, Kurian A.,Choi, YongMan,Sasaki, Kotaro,Su, Dong,Hwang, Sun-Mi,Yim, Sung-Dae,Yang, Tae-Hyun,Park, Gu-Gon,Adzic, Radoslav R. Elsevier 2016 Nano energy Vol.29 No.-
<P><B>Abstract</B></P> <P>Platinum monolayer electrocatalyst are known to exhibit excellent oxygen reduction reaction (ORR) activity depending on the type of substrate used. Here we demonstrate a relationship between the ORR electrocatalytic activity and the surface electronic structure of Pt monolayer shell induced by various IrM bimetallic cores (M=Fe, Co, Ni or Cu). The relationship is rationalized by comparing density functional theory calculations and experimental results. For an efficient Pt monolayer electrocatalyst, the core should induce sufficient contraction to the Pt shell leading to a downshift of the <SMALL>D</SMALL>-band center with respect to the Fermi level. Depending on the structure of the IrM, relative to that of pure Ir, this interaction not only alters the electronic and geometric structure but also induces segregation effects. Combined these effects significantly enhance the ORR activities of the Pt monolayer shell on bimetallic Ir cores electrocatalysts.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Core-shell structured IrM nanoparticles are better substrates than alloyed counterparts for Pt monolayer electrocatalyst. </LI> <LI> Geometric, electronic, and segregation effects together are crucial to understand the increase in ORR activity. </LI> <LI> DFT calculations demonstrate a volcano type behavior with Pt<SUB>ML</SUB>IrNi/C at the top of the curve. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Janus structured Pt-FeNC nanoparticles as a catalyst for the oxygen reduction reaction
Kuttiyiel, K.,Sasaki, K.,Park, G. G.,Vukmirovic, M.,Wu, L.,Zhu, Y.,Chen, J.,Adzic, R. Royal Society of Chemistry 2017 Chemical communications Vol.53 No.10
<P>We present a new Janus structured catalyst consisting of Pt nano-particles on Fe-N-C nanoparticles encapsulated by graphene layers for the ORR. The ORR activity of the catalyst increases under potential cycling as the unique Janus nanostructure is further bonded due to a synergetic effect. The present study describes an important advanced approach for the future design of efficient, stable, and low-cost Pt-based electrocatalytic systems.</P>
Kuttiyiel, Kurian A.,Choi, YongMan,Hwang, Sun-Mi,Park, Gu-Gon,Yang, Tae-Hyun,Su, Dong,Sasaki, Kotaro,Liu, Ping,Adzic, Radoslav R. Elsevier 2015 Nano energy Vol.13 No.-
<P><B>Abstract</B></P> <P>Given the harsh operating conditions in hydrogen/oxygen fuel cells, the stability of catalysts is one of the critical questions affecting their commercialization. We describe a distinct class of oxygen reduction (ORR) core–shell electrocatalysts comprised of nitride metal cores enclosed by thin Pt shells that is easily synthesized. The synthesis is reproducible and amenable to scale up. Our theoretical analysis and the experimental data indicate that metal nitride nanoparticle cores could significantly enhance the ORR activity as well as the durability of the core–shell catalysts as a consequence of combined geometrical, electronic and segregation effects on the Pt shells. In addition to its fuel cells application, this class of catalysts holds promise to significantly contribute in resolving the problem of platinum scarcity and furthermore indicates the guidelines for future research and development.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The non-precious metal nitrided core changes the geometric and electronic structure of PtMN/C catalysts. </LI> <LI> Nitriding increases the stability of the core-shell catalyst. </LI> <LI> DFT calculations have shown PtNiN/C at the top of the volcano curve. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Hwang, Sun-Mi,Choi, YongMan,Kim, Min Gyu,Sohn, Young-Jun,Cheon, Jae Yeong,Joo, Sang Hoon,Yim, Sung-Dae,Kuttiyiel, Kurian A.,Sasaki, Kotaro,Adzic, Radoslav R.,Park, Gu-Gon The Royal Society of Chemistry 2016 Journal of Materials Chemistry A Vol.4 No.16
<▼1><P>The high cost of Pt-based membrane electrode assemblies (MEAs) is a critical hurdle for the commercialization of polymer electrolyte fuel cells (PEFCs).</P></▼1><▼2><P>The high cost of Pt-based membrane electrode assemblies (MEAs) is a critical hurdle for the commercialization of polymer electrolyte fuel cells (PEFCs). Recently, non-precious metal-based catalysts (NPMCs) have demonstrated much enhanced activity but their oxygen reduction reaction (ORR) activity is still inferior to that of Pt-based catalysts resulting in a much thicker electrode in the MEA. For the reduction of mass transport and ohmic overpotential we adopted a new concept of catalyst that combines an ultra-low amount of Pt nanoclusters with metal–nitrogen (M–Nx) doped ordered mesoporous porphyrinic carbon (FeCo–OMPC(L)). The 5 wt% Pt/FeCo–OMPC(L) showed a 2-fold enhancement in activities compared to a higher loading of Pt. Our experimental results supported by first-principles calculations indicate that a trace amount of Pt nanoclusters on FeCo–OMPC(L) significantly enhances the ORR activity due to their electronic effect as well as geometric effect from the reduced active sites. In terms of fuel cell commercialization, this class of catalysts is a promising candidate due to the limited use of Pt in the MEA.</P></▼2>