: O646 : A (DFAFC),,,, DFAFC. PdCl 2, Pd2NH 3, H 2. CO 2,. : Pd, Vol. 15 No. 4 Nov ELECTROCHEM ISTRY : (2009)

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1 ELECTROCHEM ISTRY Vol. 15 No. 4 Nov : (2009) , 2, 2, 2, 1, 23 (1., ; 2., ) : Pd ( Pd /C)., Pd. Pd,, Pd 2. 7 nm5. 8 nm. Pd /C Pd,,Pd,. Pd3. 6 nm,. : Pd /C; ; ; ; : O646 : A, (DFAFC),,,, DFAFC., Pt., CO [ 1 ], Pt., Pd [ 224 ], CO 2,. : Pd, [ 526 ]. Pd. Pd Pd,,., Pd,., [ 7 ] Na 2 CO 3 PdCl 2, NaBH 4 Pd /C,. [ 8 ] Pd2NH 3 Pd /C, Pd2NH 3, H 2., Pd, Pd /C, Pd, Pd. 1, PdCl 2,. ph 12, XC272,N : , : , Tel: (86221) , E2mail: hyang@mail. sim. ac. cn 863 (2007AA05Z AA05Z136) ( )

2 4 : h,, Pd /C Pd20% Pd /C, Pd /C2100. Pd /C N 2 1 PdCl 2 150, h, UV2vis.,, 256 Pd /C, Pd /C2150, Pd / nm, PdCl 2 C2200 Pd /C X ( XRD ) D / PdCl 2 Pd MAX22000X ( ), CuK, ( = nm),40 kv 100 ma, Pd /C [ 9210 ]. N i, 2 /m in, 20 Pd /C 90, ( TEM ) TEM2 JEOL JEM 2100F, 200 kv..,pd, 0. 1, Pd mol L - 1 HClO mol L - 1 HClO mol L - 1 HCOOH. : mg Pd /C, 2. 5 ml 0. 5 ml 5% ( by mass) Nafion 30 m in, 10 L3 L 3 mm ( GC),, Pd 28 g cm - 2. GC,( SCE), ( RHE).,N 2 30 m in, N 2. CO, V /RHECO 15 m in, N 2 30 m in CO ( a) ( b) PdCl 2 UV2vis Fig. 1 UV2vis absorp tion spectra of the PdCl 2 without ( a) and with ( b) sodium citrate solution 2 Pd /C TEM ( a) ( b) Fig. 2 TEM image of the Pd /C2100 catalyst( a) and its particle size distribution histogram ( b)

3 nm., Pd, Pd /C, Pd /C Pd /C 3 Pd /C XRD XC272 C (002), Pd (111) Pd ( 200) Pd (220) Pd (311), Pd /C Pd,,,, Pd,. Scherrer Pd /C Pd, : nm. 4 Pd /C CO, CO0. 83 V. Pd CO 420 C cm - 2 [ 11 ],CO ( ECSA ), 1.,, Pd /C Pd, ECSA. 5 Pd /C 0. 1 mol L - 1 HClO mol L - 1 HCOOH.,Pd ( CO ), Pd., ; > 0. 6 V, Pd,,, ;, Pd PdO,Pd [ 4 ]., Pd /C2100 > Pd /C2150 > Pd /C2200 > Pd /C V (MA ) ( SA ) 1., Pd 3 Pd /C XRD Fig. 3 XRD patterns of the Pd /C catalysts heat2treated at various temperatures 4 Pd /C CO Fig. 4 CO stripp ing voltammogram s of the Pd /C catalysts in 0. 1mol L - 1 HClO 4 solution scan rate: 20 mv s - 1, inset: Pd particle size and ECSA as a funition of potential 1 Pd /C Tab. 1 The parameters of Pd /C catalysts Samp le Particle size /nm ECSA / m 2 g - 1 MA / ma mg - 1 SA / ma cm - 2 Pd /C Pd /C Pd /C Pd /C

4 4 : Pd /C 0. 1mol L - 1 HClO mol L - 1 HCOOH : 50mV s - 1 Fig. 5 Cyclic voltammogram s of the Pd /C2100, Pd /C2150, Pd /C2200 and Pd /C2250 in 0. 1mol L - 1 HClO mol L - 1 HCOOH solutions scan rate: 50mV s - 1,. Zhou [ 12 ] : Pd,,Pd, Pd5 6 nm,. Pd /C. 6 Pd /C 0. 1 mol L - 1 HClO mol L - 1 HCOOH, 0. 3 V., s, 150,Pd /C2100, Pd /C2200 Pd /C Pd /C,, Pd. Pd /C Pd,,., 3. 6 nm. 6 Pd /C 0. 3V ( a) ( b) Fig. 6 Chronoamperometric curves of the Pd /C catalysts at a given potential of 0. 3V /RHE ( a) and its normal2 ized current2time curves ( b),,pd 5. 8 nm, Pd ( References) : [ 1 ] Sun S G, Clavilier J, Bewick A. The mechanism of electrocatalytic oxidation of form ic acid on Pt ( 100 ) and Pt ( 111 ) in sulphuric acid solution: an EM IRS study[ J ]. J Electroanal Chem, 1988, 240 ( 1 /2 ) : [ 2 ] Zhang L L, Tang Y W, Bao J C, et al. A carbon2sup2 ported Pd2P catalyst as the anodic catalyst in a direct form ic acid fuel cell[ J ]. J Power Sources. 2006, 162 (1) : [ 3 ] W ang J, Kang Y, Yang H, et al. Boron2doped palla2 dium nanoparticles on carbon black as a superior cata2 lyst for form ic acid electro2oxidation [ J ]. J Phys Chem C, 2009, 113 ( 19) : [ 4 ] Hoshi N, Kida K, Nakamura M, et al. Structural effects of electrochem ical oxidation of form ic acid on single crystal electrodes of palladium [ J ]. J Phys Chem B, 2006, 110 ( 25) : [ 5 ] Park S, Xie Y, W eaver M J. Electrocatalytic pathways on carbon2supported p latinum nanoparticles: Compari2 son of particle2size2dependent rates of methanol, form ic

5 acid, and formaldehyde electrooxidation [ J ]. Lang2 muir, 2002, 18 ( 15) : [ 6 ] Kim J, Jung C, Rhee C K, et al. Electrocatalytic oxi2 dation of form ic acid and methanol on Pt deposits on Au ( 111) [ J ]. Langmuir, 2007, 23 ( 21) : [ 7 ] Chen Y( ), Tang YW (), Gao Y( ), et al. Electrocatalytic performance of Pd /C catalyst p re2 pared with imp roved liquid phase reduction method for oxidation of form ic acid [ J ]. Chinese Journal of Inor2 ganic Chem istry ( in Chinese). 2008, 24 ( 4 ) : [ 8 ] L i H Q, Sun G Q, J iang Q A, et al. Synthesis of highly dispersed Pd /C electro2catalyst with high activity for form ic acid oxidation [ J ]. Electrochem Commun, 2007, 9 (6) : [ 9 ] Zhu Y, Kang Y, Zou Z, et al. A facile p reparation of carbon2supported Pd nanoparticles for electrocatalytic oxidation of form ic acid [ J ]. Electrochem Commun, 2008, 10 ( 5) : [ 10 ] Chen Y, Tang Y W, L iu C P, et al. Room tempera2 ture p reparation of carbon supported Pt2Ru catalysts [ J ]. J Power Sources, 2006, 161 ( 1) : [ 11 ] Meng H, Sun S, Masse J, et al. Electrosynthesis of Pd single2crystal nanothorns and their app lication in the oxidation of form ic acid [ J ]. Chem Mater, 2008, 20 ( 22) : [ 12 ] Zhou W J, Lee J Y. Particle size effects in Pd2cata2 lyzed electrooxidation of form ic acid[ J ]. J Phys Chem C, 2008, 112 ( 10) : Com plex Reduction Prepara tion of Carbon Supported Pd Nanoparticle Ca ta lyst and its Electroca ta lysis for Form ic Acid Oxidation HE W ei 1, KANG Yong2yin 2, DU Chong 2, ZOU Zhi2qing 2, ZHANG Xiao2gang 1, YANG Hui 23 (1. College of M aterials Science and Eng ineering, N anjing U niversity of A eronautics and A stronau tics, N an jing , Ch ina; 2. Energy Science and Technology L aboratory, Shangha i Institute of M icrosystem and Inform a tion Technology, Ch inese A cadem y of S ciences, S hangha i , Ch ina) Abstract: A simp le p rocedure involved the comp lexing of PdCl 2 with sodium citrate followed by ethylene glycol reduction has been emp loyed for the p reparation of carbon2supported Pd nanoparticles ( Pd /C). The XRD and TEM characterizations indicate that Pd nanoparticles w ith a small particle size were well2dispersed on carbon sup2 port. The mean particle sizes of the Pd /C catalysts were found to be increased from 2. 7 to 5. 8 nm with heat2 treatments at different temperature. The mass activity of the Pd /C catalyst for form ic acid electrooxidation in2 creased w ith the decrease in Pd particle size. However, the specific activity increased w ith Pd particle size. Fur2 thermore, the Pd /C catalyst with a particle size of ca nm exhibited the best stability. Key words: Pd /C catalyst; sodium citrate; comp lex2reduction; form ic acid oxidation; particle size effect