- Nano Express
- Open Access
A facile approach to prepare silicon-based Pt-Ag tubular dendritic nano-forests (tDNFs) for solar-light-enhanced methanol oxidation reaction
© Lin et al.; licensee Springer. 2015
Received: 28 November 2014
Accepted: 30 January 2015
Published: 18 February 2015
In this paper, a facile two-step Galvanic replacement reaction (GRR) is proposed to prepare Pt-Ag tubular dendritic nano-forests (tDNFs) in ambient condition for enhancing methanol oxidation reaction (MOR) under solar illumination. In the first GRR, a homogeneous layer of silver dendritic nano-forests (DNFs) with 10 μm in thickness was grown on Si wafer in 5 min in silver nitride (AgNO3) and buffer oxide etchant (BOE) solution. In the second GRR, we utilized chloroplatinic acid (H2PtCl6) as the precursor for platinum (Pt) deposition to further transform the prepared Ag DNFs into Pt-Ag tDNFs. The catalytic performance and solar response of the Pt-Ag tDNFs toward methanol electro-oxidation are also studied by cyclic voltammetry (CV) and chronoamperometry (CA). The methanol oxidation current was boosted by 6.4% under solar illumination on the Pt-Ag tDNFs due to the induced localized surface plasmon resonance (LSPR) on the dendritic structure. Current results provide a cost-effective and facile approach to prepare solar-driven metallic electrodes potentially applicable to photo-electro-chemical fuel cells.
Direct methanol fuel cell (DMFC) has been deemed as one of the important power suppliers for renewable power applications due to the high energy-conversion efficiency thereof [1,2]. One of the major issues of DMFCs is the slow process of methanol oxidation reaction (MOR), which directly limits the efficiency of DMFC . Traditionally, platinum (Pt)-based alloy has been used as common a catalyst in MOR. In the past two decades, many bimetallic catalysts have been proposed to enhance the efficiency of MOR, including Pt-Ru , Pt-Ag , Pt-Au , etc. Recently, metal-oxide-supported Pt catalysts, including Pt-TiO2 , Pt-ZnO , and PtRu-TiO2 , were proposed to boost methanol oxidation under ultraviolet (UV) illumination for photo-electrochemical fuel cells . Although over 60% of enhancement on MOR has been realized under UV illumination (365 nm, 100 W) , seldom, reports discussed the solar enhancement toward MOR, especially on pure metallic catalysts. In this paper, a facile two-step Galvanic replacement reaction (GRR) is proposed to prepare Pt-Ag tubular dendritic nano-forests (tDNFs) in ambient condition for enhancing MOR under solar illumination.
In preparation of the aforementioned bimetallic catalysts, GRR was widely employed to provide a simple and cost-effective fabrication approach [10,11]. By utilizing the difference in the standard reduction potentials, replacement between two metals can be easily achieved at ambient condition. Many metal composites prepared by GRR have been reported, including Ag-Au [12,13], Pt-Au [14,15], Pd-Pt [16,17], Ag-Pt [18-21], Pd-Ag [22,23], Cu-Pd , and Cu-Ag . However, most of the studies focused on the preparation of non-supported catalysts. The prepared catalysts suspended in the solution could be hardly collected and deposited on the electrodes in the electrochemical cells. Moreover, the effective electrochemical surface area of the non-supported catalysts could be greatly sacrificed due to the aggregation of nano-catalysts in brushing or printing process [4,26].
In order to prepare metallic nanostructures directly on supporting substrates, fluoride-assisted Galvanic replacement reaction (FAGRR) was proposed to synthesize three-dimensional metallic dendrites on silicon-based substrates [27-31]. Recently, Ye et al. reported a facile method for preparing self-assembled silver dendrites on silicon wafer in fluoride and silver nitride solution [27,29] for improving surface-enhanced Raman spectroscopy (SERS) [27-29,31]. However, the prepared silver dendrites could be easily contaminated by sulfur or oxygen to from Ag2O or Ag2S at ambient [32,33], which directly limits the applications for catalytic reactions.
In this paper, we propose the preparation of Si-based Pt-Ag tDNFs for solar-light-enhanced MOR by a two-step facile GRR at ambient without any energy input. This self-assembled Pt-Ag tDNFs not only benefit from the large aspect surface area provided by the Ag dendrites but also the localized surface plasmon resonance (LSPR) effect for the enhancement of methanol electrode-oxidation. Besides, the Pt outer shell of Pt-Ag tDNFs provides a protection to Ag and thus greatly enhances the stability of the prepared photo-electrodes.
Preparation of Ag DNFs and Pt-Ag tDNFs
Surface morphology and material characterization
Scanning electron microscope (SEM; Hitachi FE 4300 in Instrument Technology Research Center (ITRC); Hitachi, Tokyo, Japan) and field emission transmission electron microscope (TEM; JOEL JEM2100F in National Chung Hsing University (NCHU); JOEL Ltd., Tokyo, Japan) were employed to investigate the surface profile of the prepared samples. Energy-dispersive X-ray spectroscopy (EDS) was used to analyze the elemental composition.
Investigation on photo-enhanced electrochemical reactions
Electrochemical reactions were measured by a potentiostat (Autolab PGSTAT302N in ITRC) in a rectangular three-electrode reaction tank (500 mL) made by quartz. The prepared samples with projection area of 1 cm2 were used as the working electrodes, Pt-coated titanium mesh (25 cm2) as the counter electrode, and saturated calomel electrode (SCE) as the reference electrode. Cyclic voltammetry (CV) and chronoamperometry (CA) were used to evaluate the catalytic capability for methanol electro-oxidation. A solar simulator (SADHUDESIGN; class B; 400 to 1,000 nm; 1,000 W m−2) was employed for the illumination experiments. All chemicals used in this experiment were reagent grade. The resistance of DI water was 18.2 MΩ. All experiments were conducted at 22°C at ambient pressure.
Results and discussion
Surface morphology of Ag DNFs
Surface morphology of Pt-Ag tDNFs
Photo-enhancement on methanol electro-oxidation
The mechanism of LSPR enhancement on electro-catalysis is a synergetic process, comprising plasmonic heating, magnification of local electromagnetic field, electron injection process, etc. [40-43]. Although more experiments are required to further elucidate the energy transfer process, current results provided a direct observation on the oxidation current enhancement and OCP variation under solar illumination in methanol electro-oxidation. The cost-effective and easily-prepared silicon-based Pt-Ag tDNFs are active to solar illumination and have high potential to serve as promising candidates for photo-electrochemical fuel cells.
In this letter, focus is placed on the facile two-step GRR to prepare silicon-based Pt-Ag tDNFs in ambient condition for enhancing MOR under solar illumination. The FAGRR enables the fast growth of Ag NDFs on the silicon wafer within 5 min. Following that, the chloroplatinic acid further transformed the surface of Ag NDFs into Pt nano-shells and emptied the structure simultaneously within another 5 min. The prepared Pt-Ag tDNFs showed solar response (6.4% of enhancement on oxidation current) toward methanol oxidation. The solar response is attributed to the strong LSPR provided by the Ag DNFs. This cost-effective Pt-Ag tDNFs could be a promising candidate for photo-electrochemical fuel cells.
The authors would like to express appreciation to the Ministry of Science and Technology of the Republic of China, Taiwan, for the financial supports under the following contract numbers: MOST103-2321-B-007-004, NSC102-2321-B-007-006, MOST103-3113-E-007-006, NSC102-2627-M-007-002, MOST104-2623-E-492-001-ET, and NSC102-2221-E-492-003. Also, we appreciate Mr. Chih-Jung Lu at the Instrument Center in National Chung Hsing University for his help in TEM operation.
- Li X, Faghri A. Review and advances of direct methanol fuel cells (DMFCs) part I: design, fabrication, and testing with high concentration methanol solutions. J Power Sources. 2013;226:223–40.View ArticleGoogle Scholar
- Olah GA. Beyond oil and gas: the methanol economy. Angew Chem Int Ed. 2005;44:2636–9.View ArticleGoogle Scholar
- Liu H, Song C, Zhang L, Zhang J, Wang H, Wilkinson DP. A review of anode catalysis in the direct methanol fuel cell. J Power Sources. 2006;155:95–110.View ArticleGoogle Scholar
- Tsai M-C, Yeh T-K, Tsai C-H. An improved electrodeposition technique for preparing platinum and platinum-ruthenium nanoparticles on carbon nanotubes directly grown on carbon cloth for methanol oxidation. Electrochem Commun. 2006;8:1445–52.View ArticleGoogle Scholar
- Feng Y-Y, Bi L-X, Liu Z-H, Kong D-S, Yu Z-Y. Significantly enhanced electrocatalytic activity for methanol electro-oxidation on Ag oxide-promoted PtAg/C catalysts in alkaline electrolyte. J Catal. 2012;290:18–25.View ArticleGoogle Scholar
- Zeng J, Yang J, Lee JY, Zhou W. Preparation of carbon-supported core-shell Au-Pt nanoparticles for methanol oxidation reaction: the promotional effect of the Au core. J Phys Chem B. 2006;110:24606–11.View ArticleGoogle Scholar
- Lin C-T, Huang HJ, Yang J-J, Shiao M-H. A simple fabrication process of Pt-TiO2 hybrid electrode for photo-assisted methanol fuel cells. Microelectronic Engineering. In Press, Accepted Manuscript.Google Scholar
- Su C-Y, Hsueh Y-C, Kei C-C, Lin C-T, Perng T-P. Fabrication of high-activity hybrid Pt@ZnO catalyst on carbon cloth by atomic layer deposition for photoassisted electro-oxidation of methanol. J Phys Chem C. 2013;117:11610–8.View ArticleGoogle Scholar
- Drew K, Girishkumar G, Vinodgopal K, Kamat PV. Boosting fuel cell performance with a semiconductor photocatalyst: TiO2/Pt-Ru hybrid catalyst for methanol oxidation. J Phys Chem B. 2005;109:11851–7.View ArticleGoogle Scholar
- Xia X, Wang Y, Ruditskiy A, Xia Y. 25th anniversary article: galvanic replacement: a simple and versatile route to hollow nanostructures with tunable and well-controlled properties. Adv Mater. 2013;25:6313–33.View ArticleGoogle Scholar
- Carraro C, Maboudian R, Magagnin L. Metallization and nanostructuring of semiconductor surfaces by galvanic displacement processes. Surf Sci Rep. 2007;62:499–525.View ArticleGoogle Scholar
- Au L, Lu X, Xia Y. A comparative study of galvanic replacement reactions involving Ag nanocubes and AuCl2− or AuCl4−. Adv Mater. 2008;20:2517–22.View ArticleGoogle Scholar
- Yang L, Qi M, Jin M. Fabrication of SBA-15 supported Ag@Au-Ag metal-core/alloy-shell nanoparticles for CO oxidation. CrystEngComm. 2013;15:2804–8.View ArticleGoogle Scholar
- Chen L, Kuai L, Yu X, Li W, Geng B. Advanced catalytic performance of Au–Pt double-walled nanotubes and their fabrication through galvanic replacement reaction. Chem Eur J. 2013;19:11753–8.View ArticleGoogle Scholar
- Kim Y, Kim HJ, Kim YS, Choi SM, Seo MH, Kim WB. Shape- and composition-sensitive activity of Pt and PtAu catalysts for formic acid electrooxidation. J Phys Chem C. 2012;116:18093–100.View ArticleGoogle Scholar
- Zhang H, Jin M, Wang J, Li W, Camargo PHC, Kim MJ, et al. Synthesis of Pd–Pt bimetallic nanocrystals with a concave structure through a bromide-induced galvanic replacement reaction. J Am Chem Soc. 2011;133:6078–89.View ArticleGoogle Scholar
- Wang L, Yamauchi Y. Metallic nanocages: synthesis of bimetallic Pt–Pd hollow nanoparticles with dendritic shells by selective chemical etching. J Am Chem Soc. 2013;135:16762–5.View ArticleGoogle Scholar
- He W, Wu X, Liu J, Zhang K, Chu W, Feng L, et al. Formation of AgPt alloy nanoislands via chemical etching with tunable optical and catalytic properties. Langmuir. 2009;26:4443–8.View ArticleGoogle Scholar
- Zhang W, Yang J, Lu X. Tailoring galvanic replacement reaction for the preparation of Pt/Ag bimetallic hollow nanostructures with controlled number of voids. ACS Nano. 2012;6:7397–405.View ArticleGoogle Scholar
- Bansal V, O’Mullane AP, Bhargava SK. Galvanic replacement mediated synthesis of hollow Pt nanocatalysts: significance of residual Ag for the H2 evolution reaction. Electrochem Commun. 2009;11:1639–42.View ArticleGoogle Scholar
- Kim MR, Lee DK, Jang D-J. Facile fabrication of hollow Pt/Ag nanocomposites having enhanced catalytic properties. Appl Catal B Environ. 2011;103:253–60.View ArticleGoogle Scholar
- Huang J, Vongehr S, Tang S, Lu H, Meng X. Highly catalytic Pd–Ag bimetallic dendrites. J Phys Chem C. 2010;114:15005–10.View ArticleGoogle Scholar
- Liu M, Lu Y, Chen W. PdAg nanorings supported on graphene nanosheets: highly methanol-tolerant cathode electrocatalyst for alkaline fuel cells. Adv Funct Mater. 2013;23:1289–96.View ArticleGoogle Scholar
- Mohl M, Dobo D, Kukovecz A, Konya Z, Kordas K, Wei J, et al. Formation of CuPd and CuPt bimetallic nanotubes by galvanic replacement reaction. J Phys Chem C. 2011;115:9403–9.View ArticleGoogle Scholar
- Chen X, Cui C-H, Guo Z, Liu J-H, Huang X-J, Yu S-H. Unique heterogeneous silver–copper dendrites with a trace amount of uniformly distributed elemental Cu and their enhanced SERS properties. Small. 2011;7:858–63.View ArticleGoogle Scholar
- Lin C-T, Huang HJ, Yang J-J, Shiao M-H. A simple fabrication process of Pt-TiO2 hybrid electrode for photo-assisted methanol fuel cells. Microelectron Eng. 2011;88:2644–6.View ArticleGoogle Scholar
- Ye W, Shen C, Tian J, Wang C, Bao L, Gao H. Self-assembled synthesis of SERS-active silver dendrites and photoluminescence properties of a thin porous silicon layer. Electrochem Commun. 2008;10:625–9.View ArticleGoogle Scholar
- Fei Chan Y, Xing Zhang C, Long Wu Z, Mei Zhao D, Wang W, Jun Xu H, et al. Ag dendritic nanostructures as ultrastable substrates for surface-enhanced Raman scattering. Appl Phys Lett. 2013;102:183118-183118-183115.Google Scholar
- Ye W, Shen C, Tian J, Wang C, Hui C, Gao H. Controllable growth of silver nanostructures by a simple replacement reaction and their SERS studies. Solid State Sci. 2009;11:1088–93.View ArticleGoogle Scholar
- Lin C-T, Yu M-H, Su J, Chen P-L, Shiao M-H, Nemcsics A, et al. Localized electroless Ag plating at a tip apex for scanning Kelvin probe microscopy. Jpn J Appl Phys. 2013;52:06GF03-06GF03-04.Google Scholar
- Gutés A, Carraro C, Maboudian R. Silver dendrites from galvanic displacement on commercial aluminum foil as an effective SERS substrate. J Am Chem Soc. 2010;132:1476–7.View ArticleGoogle Scholar
- Saber TMH, El Warraky AA. AES and XPS study on the tarnishing of silver in alkaline sulphide solutions. J Mater Sci. 1988;23:1496–501.View ArticleGoogle Scholar
- McMahon MD, Lopez R, Meyer III HM, Feldman LC, Haglund Jr RF. Rapid tarnishing of silver nanoparticles in ambient laboratory air. Appl Phys B. 2005;80:915–21.View ArticleGoogle Scholar
- Chen HM, Liu R-S, Asakura K, Lee J-F, Jang L-Y, Hu S-F. Fabrication of nanorattles with passive shell. J Phys Chem B. 2006;110:19162–7.View ArticleGoogle Scholar
- Otten MT. High-angle annular dark-field imaging on a tem/stem system. Journal of Electron Microscopy Technique. 1991;17:221–30.View ArticleGoogle Scholar
- Gonzalez E, Arbiol J, Puntes VF. Carving at the nanoscale: sequential galvanic exchange and kirkendall growth at room temperature. Science. 2011;334:1377–80.View ArticleGoogle Scholar
- Shim JH, Yang J, Kim S-j, Lee C, Lee Y. One dimensional Ag/Au/AgCl nanocomposites stemmed from Ag nanowires for electrocatalysis of oxygen reduction. J Mater Chem. 2012;22:15285–90.View ArticleGoogle Scholar
- Han X, Wang D, Huang J, Liu D, You T. Ultrafast growth of dendritic gold nanostructures and their applications in methanol electro-oxidation and surface-enhanced Raman scattering. J Colloid Interface Sci. 2011;354:577–84.View ArticleGoogle Scholar
- Huang X, Tang S, Mu X, Dai Y, Chen G, Zhou Z, et al. Freestanding palladium nanosheets with plasmonic and catalytic properties. Nat Nano. 2011;6:28–32.View ArticleGoogle Scholar
- Adleman JR, Boyd DA, Goodwin DG, Psaltis D. Heterogenous catalysis mediated by plasmon heating. Nano Lett. 2009;9:4417–23.View ArticleGoogle Scholar
- Fei Chan Y, Xing Zhang C, Long Wu Z, Mei Zhao D, Wang W, Jun Xu H, et al. Ag dendritic nanostructures as ultrastable substrates for surface-enhanced Raman scattering. Applied Physics Letters 2013;102:183118–183118-5.Google Scholar
- Kale MJ, Avanesian T, Christopher P. Direct photocatalysis by plasmonic nanostructures. ACS Catal. 2013;4:116–28.View ArticleGoogle Scholar
- Hou W, Cronin SB. A review of surface plasmon resonance-enhanced photocatalysis. Adv Funct Mater. 2013;23:1612–9.View ArticleGoogle Scholar
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.