DOI: 10.1002/cphc.201300772 Palladium- and Gold-Nanoparticle-Modified Porous Carbon as a High-Power Anode for Lithium-Ion Batteries Subash Chandrabose Raghu,* [a] Mani Ulaganathan, [b] Vanchiappan Aravindan,* [b] and Tuti Mariana Lim [a, c] &&1) Change to title OK? 2) The Abstract has been removed (Communications published in ChemPhysChem do not contain an Abstract)&&Rechargeable lithium-ion batteries (LIBs) are one of the most promising power packs for electric vehicles (EV) and hybrid electric vehicles (HEV). [1] Nevertheless, such ap- plications require high-performance LIBs with high energy and power densities. However, the current LIB technology, compris- ing lithium-containing transition-metal oxides as the cathode and graphite as the anode, suffers to deliver the necessary power to drive those vehicles. [2] &&OK?&& This is mainly due to the low performance of graphitic anodes, especially re- garding high rate operations. Therefore, an anode material with lower operating potential, high capacity, high rate perfor- mance, low cost and environmental friendliness is anticipat- ed. [3] Conversion and alloy-type anodes are also explored as high-power anodes; however, such anodes endue a huge amount of irreversible capacity loss, a large unit cell volume expansion and a higher operating potential than graphitic anodes, which prevents their use as a potential anode. [4] There- fore, much attention is paid to the development of carbona- ceous materials other than graphite, such as non-graphitic car- bons. Due to the lack of ordering in the structure (disordered carbons), such non-graphitic carbons can accommodate a higher amount of Li than conventional graphite (372 mAh g À1 ) with good cyclability. [3a] Recent studies clearly demonstrate the use of disordered porous carbon as an excel- lent alternative anode material for LIBs due to its higher specif- ic capacity (400–1660 mAh g À1 ), low cost and easy preparation compared to conventional graphite anodes. [3c, d, 5] The high spe- cific capacity of disordered porous carbon is mainly due to the larger surface-to-volume ratio, which causes the formation of lithium multilayers on graphene sheets or the binding of lithi- um on the surface of the carbon layers and in the nanocavitie- s. [3a, 5c, 6] A slightly higher operating voltage and higher irreversi- ble capacity loss is a major issue for such disordered hard car- bons compared to graphite. [3d] Therefore, to evade this issue, some modifications such as metal-nanoparticles decorations on the disordered porous carbons are warranted to employ them as high-power anodes. [1d] Moreover, Pd and Pt decoration were already carried out for graphitic anodes to improve the electrochemical profiles. [7] In this line, an attempt has been made for the decoration of such porous carbons by Au and Pd nanoparticles with a view to identify the novel electrode mate- rials by improving the performances such as high specific ca- pacity at high current rate without compromising the cyclabili- ty. A facile chemical reduction process is employed to decorate the metallic nanoparticles (Au/Pd) with a controlled amount of 5 wt. % over commercially available porous carbons. The metal-nanoparticle-decorated powders are subjected to vari- ous electrochemical characterizations in a half-cell configura- tion, as described in detail herein. Experimental Section For the metallic decoration, analytical-grade AuCl 3 and PdCl 2 were used as the starting materials along with porous carbon (vulcon XC-72). In a typical synthesis, stoichiometric amounts of metal chlorides (5 wt.%) were dissolved in 10 mL of distilled water. Then, porous carbon (2 g) was dispersed in each AuCl 3 and PdCl 2 con- taining solutions and stirred for 24 h using an ultra-sonicator. The nature of the solution was adjusted to slightly alkaline (pH 8) using a sodium hydroxide solution. The reduction process was carried out for AuCl 3 /PdCl 2 containing solutions by adding 1 mL of a 0.1 m NaBH 4 solution under controlled conditions, followed by washing (3–4 times) using deionised water for removing any traces of im- purities. Finally, the powders were dried at 60 8C in vacuum for 2 h. Morphological features of the Au/Pd-decorated porous carbon and pristine porous carbon were studied with a high-resolution trans- mission electron microscope (HR-TEM, JEOL, JEM-2100). The struc- tural properties were investigated by powder X-ray diffraction (XRD) on a Bruker AXS D8 advance equipped with Cu K a radiation. Composite electrodes were formulated by mixing the active mate- rial with a polyvinylidine fluoride (PVdF) binder at a weight ratio of 90:10 in 1-methyl-2-pyrrolidinone (NMP). The slurry was coated on the copper foil by the doctor blade method and dried in vacuum at 100 8C for 5 h. The active mass loading was found to be 2.5– 3 mg per 16 mm area electrode. All the electrochemical studies were carried out using a standard CR 2032 coin-cell. The test cells were assembled with carbon materials as the working electrode and a lithium foil as the counter electrode, separated by a micropo- rous polypropylene film. 1 m (mol dm À3 ) LiPF 6 in a tertiary mixture of ethylene carbonate/di-methyl carbonate/di-ethyl carbonate (EC/ DMC/DEC, 1:1:1 by vol.) was used as the electrolyte solution. Cyclic voltammograms (CV) and electrochemical impedance spectroscopy (EIS) measurements were carried out using an electrochemical workstation (Solartron 1470E) at ambient conditions. CV measure- ments were performed between 0.01–3.0 V (vs. Li) at a slow scan [a] Dr. S. C. Raghu, Prof. T. M. Lim School of Civil and Environmental Engineering Nanyang Technological University, Block N1 Nanyang Avenue, Singapore 639798 (Singapore) E-mail : subraghu_0612@yahoo.co.in [b] Dr. M. Ulaganathan, Dr. V. Aravindan Energy Research Institute, @ NTU (ERI@N) Nanyang Technological University, Research Techno Plaza 50 Nanyang Drive, Singapore 637553 (Singapore) E-mail : aravind_van@yahoo.com [c] Prof. T. M. Lim School of Life Sciences and Chemical Technology Ngee Ann Polytechnic, Singapore 599489 (Singapore)  2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim ChemPhysChem 2013, 14,1–4 1 These are not the final page numbers! ÞÞ CHEMPHYSCHEM COMMUNICATIONS 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 10 10 11 11 12 12 13 13 14 14 15 15 16 16 17 17 18 18 19 19 20 20 21 21 22 22 23 23 24 24 25 25 26 26 27 27 28 28 29 29 30 30 31 31 32 32 33 33 34 34 35 35 36 36 37 37 38 38 39 39 40 40 41 41 42 42 43 43 44 44 45 45 46 46 47 47 48 48 49 49 50 50 51 51 52 52 53 53 54 54 55 55 56 56 57 57