制作双催化层结构的PEMFC电极.该双催化层由含有Nafion的内催化层、无Nafion的外催化层组成.循环伏安测试表明,未与Nafion直接接触的外催化层Pt/C催化剂也参与发生在"Pt/Nafion"界面氢原子的吸脱附反应和Pt表面含氧粒子的电化学氧化还原.当电势扫描速率较低时,未与Nafion直接接触的外层Pt/C催化剂,其对氢脱附电流的贡献和直接与Nafion接触的内催化层的Pt/C催化剂大致相当.以双催化层电极作PEMFC阴极,单电池(PEMFC)极化曲线测试表明,其阴极外催化层能明显地提高该单电池在活化极化区的输出性能.进一步证明了PEMFC阴极外催化层不与Nafion直接接触的Pt/C催化剂可通过其表面吸附含氧粒子的表面扩散参与发生在"Pt/Nafion"界面氧的电化学还原反应.上述实验为设计PEMFC电极提供了一定的新思路.
A PEMFC electrode consisting of dual-layer catalyst layer(CL) was fabricated in this work.The outer CL was Nafion-free,while the inner CL was Nafion-bonded.The effects of Pt/C catalyst in the outer CL that did not contact with Nafion on the current generation in PEMFC electrodes were investigated.Cyclic voltammetric studies indicated that the Pt/C catalyst in the outer CL without direct contact with Nafion was still electrochemically active in taking part in the adsorption/desorption of hydrogen and the electrochemical oxidation/reduction of the oxygen-containing species occurring at the interface of "Pt/Nafion" in the inner CL.The polarization curves showed that the output voltage of the single cell was enhanced obviously by the outer CL when the current density was lower than 0.2A/cm2.The phenomena indicated that the Pt/C catalyst without direct contact with Nafion also participated in the electrochemical reduction of oxygen at the interface of "Pt/Nafion" via the surface diffusion of the adsorbed oxygen-containing species.
[1]Steele B C H,Heinzel A.Materials for fuel-cell tech-nologies[J].Nature,2001,414(6861):345-352.
[2]Zhang X W,Shi P F,Dual-bonded catalyst layer struc-ture cathode for PEMFC[J].Electrochemistry Commu-nications,2006,8(8):1229-1234.
[3]Ou S(欧胜),Kong D W(孔德文),He R(何锐),etal.Study of current generation mechanism in PEMFCcatalyst layer[J].Journal of Wuhan University ofTechnology(in Chinese),2006,28(z1):417-421.
[4]McBreen J.Voltammetric studies of electrodes in con-tact with ionomeric membranes[J].J Electrochem Soc,1985,132(5):1112-1116.
[5]Jing J H,Wu B L,Cha C S,et al.Application of SPEcomposite microelectrodes to the study of the spillover ofadsorbed species on electrode surfaces[J].J.Electro-anal chem,1998,445(1~2):13-16.
[6]Tu W Y,Liu W J,Cha C S,et al.Study of the pow-der/membrane interface by using the powder microelec-trode technique.I.The pt-black/Nafion○Rinterfaces[J].Electrochim Acta,1998,43(24):3731-3739.
[7]Liu W J,Wu B L,Cha C S.Surface diffusion and thespillover of H-adatoms and oxygen-containing surfacespecies on the surface of carbon black and Pt/C porouselectrodes[J].J Electroanal Chem,1999,476(2):101-108.
[8]Lin R B,Shih S M.Kinefic analysis of the hydrogen ox-idation reaction on Pt-black/Nafion electrode[J].Jour-nal of Solid State Electrochemistry,2006,10(4):243-249.
[9]Wang X F,Zhan D P,Fu Y Y,et al.Spillover on aplatinum electrode modified by MWNTs[J].ChineseChemical Letters,2004,15(12):1480-1482.
[10]Wang X L,Zhang HM,Zhang J L,et al.Micro-por-ous layer with composite carbon black for PEM fuelcells[J].Electrochimica Acta,2006,51(23):4909-4915.
[11]Cha C S(查全性).Introduction to the kinetics of e-lectrode processes[M].Beijing:Science Press,2002:134-135.
