An environmentally friendly one-pot synthesis method by the ultrasound assistance for the decoration of ultrasmall Pd-Ag NPs on graphene as high active anode catalyst towards ethanol oxidation
Introduction
Nowadays, direct ethanol fuel cells (DEFCs) have been extensively studied as ideal alternative for power source on account of their security, high efficiency, renewable capability and low environmental pollutant emission [1], [2], [3], [4], [5], [6]. Nonetheless, the application of DEFCs in commercial level still faces crucial barriers such as low activity, insufficient long-term durability as well as high-price of catalysts. To resolve these issues, an extensive spectrum of routes has been reported with respect to the tailored design of the shape, dispersity, size, and chemical components of a catalyst.
Since now, a broad spectrum of studies has been dedicated to Pt-based catalysts while researchers believe that these materials are good alternatives for DEFCs [7], [8]. Nonetheless, high price and limited resources ultimately may hinder their utilization in a commercial application. Moreover, a serious problem of these materials is CO poisoning, which limits their usage as catalysts in the fuel cells [1], [2], [3], [4], [5], [6]. A key challenge in the commercial application of DEFCs is the tailored design of highly active, durable and inexpensive catalysts. Therefore, it is important to find a stable, active and inexpensive alternative for the replacement of Pt-based nanocatalysts. Recently, Pd-based nanomaterials, particularly Pd-transition metal alloys, have appeared as efficient alternatives to Pt-based nanomaterials owing to their high performance, higher resistance to poisoning as well as inexpensiveness. Pd-based nanocatalysts are nearly inert to oxidation of alcohol in acid media while they are more active than Pt for electrooxidation process of ethanol in basic media [9], [10], [11], [12], [13]. Moreover, Pd-based binary nanocatalysts, compared to pure Pd, demonstrate higher catalytic activity toward ethanol oxidation reaction (EOR) [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14].
It was proved that the performance of a catalyst is seriously affected by the size, synergistic effect, shape and distribution of a catalyst [15], [16]. Accordingly, a broad spectrum of routes has been developed to create high-performance Pd-based catalysts. The approaches include alloying Pd with various elements [17], [18], [19], and production of Pd nanocrystals [20], [21], [22]. Alloying Pd with various metals is considered as a good method that can not only enhance the electrocatalytic performance, but also decrease the loading of Pd metal. In recent years, more studies have used transition metals such as Au [16], Co [23], Ni [24], Ag [25], and Cu [18] combined with Pd to promote the catalytic performance of Pd-based nanocatalysts.
Until now, numerous routes have been successfully reported to create Pd-based binary catalysts which often need a multistep and complicated process. Therefore, researchers have focused on the finding the simple and one-pot synthesis approaches of Pd-based binary catalysts [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35]. In recent years, profuse one-pot synthesis methods have been proposed to fabricate the Pd-based binary catalysts. Unfortunately, the utilization of surfactants (e.g. PVP (poly (vinyl pyrrolidone), etc.) and reductant reagents (e.g. NaBH4, EG (ethylene glycol), etc.) are serious problems in the development of one-pot synthesis approaches for the creation of Pd-based binary catalysts. Both materials (surfactants and reducing reagents) are highly expensive and injurious compounds with regard to both environment and the human health. Moreover, coalescence of metal NPs may be hindered by employing the surfactant materials. However, application of surfactant materials leads to the blockage of active sites on the surface of nanoparticles on account of the interaction with the surface of nanoparticles which leads to the degradation of catalytic activity. Therefore, these materials are injurious for catalysis process. Besides, the well-disperse and small size of Pd NPs possess extraordinary catalytic efficiency. Nonetheless, Pd NPs created with the contractual reduction route offer poor dispersity as well as huge average sizes and lead to the coalescence of Pd NPs. Likewise, the creation of Pd-based bimetallic catalysts requires a very high temperature. The utilization of high temperature goes along with the coalescence of NPs while this phenomenon is accompanied by loss of ECSA (electrochemical surface area) as well as electrocatalytic performance of a nanocatalyst. Hence, tailored design of the experiments to provide the desirable conditions (e.g. simple, one-pot synthesis, surfactant and reductant free, low temperature and environmentally friendly way) is a vital index to synthesize and commercialization of a nanocatalyst. In addition, it is essential to select the support materials appropriately in order to prevent coalescence of NPs which reduces the surface area and electrocatalytic efficiency [36], [37]. Graphene nanosheets show a unique structure of two-dimensional (2D) sheets that are one atom thick and composed of sp2-bonded carbon atoms. They provide amazing characters such as outstanding specific surface area (≈2600 m2g−1), high thermal conductivity (5000 W mK−1), high electron mobility (2.5 × 105 cm2 V−1 s−1), and strong chemical stability. The graphene nanosheets possess an opportunity for using 2D materials as the conductive sheets to anchor electrocatalysts in polymer electrolyte membrane fuel cells (PEMFCs) [38], [39], [40], [41].
In the materials chemistry, the ultrasonic-assisted strategy is known as an efficient and powerful method for the synthesis of highly active noble metal, due to its relatively simple device and time-saving operating process. Ultrasonic irradiation provides unusual physical and chemical effects that are derived from acoustic cavitation. A mechanism for all of the sonoelectrochemical generation of nanosize metals has been proposed where metallic ions are decreased utilizing a short current pulse. In the following, NPs are also dislodged by the ultrasonic pulse. It must be noted that metallic NPs in solution have the tendency to be assembled automatically while the speed of the Ostwald ripening process is boosted which results in smaller primary NPs [42], [43], [44], [45], [46], [47], [48], [49], [50].
Herein, an environmentally friendly method was employed for the decoration of ultrasmall Pd-Ag NPs on G support (Pd-Ag/G). This way offers extraordinary advantages in comparison to other approaches such as one-pot synthesis, being surfactant and reductant free, facile and being environmentally friendly and having low temperature. The green and one-pot synthesis route was occurred based on the decomposition of silver formate at 298 K followed by a galvanic replacement reaction (GRR) Ag with Pd2+ ions at room temperature (RT). Resultant Pd-Ag/G reveals extraordinary electrocatalytic performance toward EOR.
Section snippets
Materials
Alumina (Al2O3), formic acid (HCOOH) (98–100%), sodium hydroxide (NaOH), silver nitrate (AgNO3), sodium carbonate (Na2CO3), graphite powder, palladium (II) chloride (PdCl2, 56%) and ethanol (C2H5OH) were purchased from Merck Co. Chitosan ([2-amino-2-deoxy-(1-4)-b-d-glucopyranose]), (CH) with medium molecular weight, 400,000 Da, was provided from Fluka company and utilized as received. Acetic acid was diluted to a 1% aqueous solution before use. Doubly distilled water was used throughout the
Synthesis and characterization of Pd-Ag/G
An environmentally friendly method by the assistance of ultrasound was employed to decorate the ultrasmall Pd-Ag NPs on graphene support. The Pd-Ag/G catalyst was synthesized during the decomposition of silver formate at 298 K under ultrasound irradiation followed by GRR approach. In comparison to the preceding literature, this way possesses several advantages (e.g. surfactant and reductant free, fast, environmentally friendly strategy, one-pot synthesis, low temperature, and facile way). In
Conclusion
In summary, an environmentally friendly method has been introduced to prepare ultrasmall Pd-Ag nanoparticle decorated on graphene support (Pd-Ag/G). This route offers extraordinary advantages in comparison to other approaches such as being surfactant and reductant free, one-pot synthesis, low temperature, simple and environmentally friendly. Decoration of ultrasmall Pd-Ag NPs on graphene support was well confirmed by employing the TEM, XRD, and EDS analyses. The TEM micrographs display the
References (73)
- et al.
Electro-oxidation of mixed reactants of ethanol and formate on Pd/C in alkaline fuel cells
J. Energy Chem.
(2016) - et al.
Novel fabrication of PdCu nanostructures decorated on graphene as excellent electrocatalyst toward ethanol oxidation
Int. J. Hydr. Ener
(2017) - et al.
A rapid synthesis of high surface area PdRu nanosponges: composition-dependent electrocatalytic activity for formic acid oxidation
J. Energy Chem.
(2017) - et al.
Ultrafast synthesis of flower-like ordered Pd3Pb nanocrystals with superior electrocatalytic activities towards oxidation of formic acid and ethanol
J. Power Sources
(2016) - et al.
Pt and PtRu catalyst bilayers increase efficiencies for ethanol oxidation in proton exchange membrane electrolysis and fuel cells
J. Power Sources
(2017) - et al.
A genetically optimized kinetic model for ethanol electro-oxidation on Pt-based binary catalysts used in direct ethanol fuel cells
J. Power Sources
(2017) - et al.
Pd–Ni electrocatalysts for efficient ethanol oxidation reaction in alkaline electrolyte
Int. J. Hydr. Energy
(2011) - et al.
Promotion of palladium catalysis by silver for ethanol electro-oxidation in alkaline electrolyte
Int. J. Hydr. Energy
(2014) - et al.
Surface Palladium rich CuxPdy/carbon catalysts for methanol and ethanol oxidation in alkaline media
Electrochim. Acta
(2015) - et al.
Synthesis and electrocatalytic alcohol oxidation performance of Pd–Co bimetallic nanoparticles supported on graphene
Int. J. Hydr. Energy
(2014)
Palladium-copper electrocatalyst for promotion of oxidation of formate and ethanol in alkaline media
Electrochim. Acta
Synthesis of bimetallic PdAu nanoparticles for formic acid oxidation
Electrochim. Acta
Facile fabrication of novel PdRu nanoflowers as highly active catalysts for the electrooxidation of methanol
J. Colloid Interface Sci.
Tungsten carbide promoted Pd and Pd-Co electrocatalysts for formic acid electrooxidation
J. Power Sources
Methanol electro-oxidation on Ni@ Pd core-shell nanoparticles supported on multi-walled carbon nanotubes in alkaline media
Int. J. Hydr. Energy
Composition-tuned porous Pd-Ag bimetallic dendrites for the enhancement of ethanol oxidation reactions
J. Alloy Compd.
Palladium-copper electrocatalyst for the promotion of the electrochemical oxidation of polyalcohol fuels in the alkaline direct alcohol fuel cell
Appl. Catal. B: Environ.
Simple one-pot preparation of Pd-on-Cu nanocrystals supported on reduced graphene oxide for enhanced ethanol electrooxidation
Electrochim. Acta
One-pot synthesis of Palladium Silver nanoparticles decorated reduced graphene oxide and their application for ethanol oxidation in alkaline media
Electrochim Acta
One-pot synthesis of gold–palladium@palladium core–shell nanoflowers as efficient electrocatalyst for ethanol electrooxidation
J. Power Sources
One-pot synthesis of carbon-supported monodisperse palladium nanoparticles as excellent electrocatalyst for ethanol and formic acid oxidation
J. Power Sources
One-step synthesis of carbon-supported Pd–Pt alloy electrocatalysts for methanol tolerant oxygen reduction
Electrochem. Commun.
Nitrogen-doped reduced graphene oxide supports for noble metal catalysts with greatly enhanced activity and stability
Appl. Catal. B. Environ.
Nano-size boron carbide intercalated graphene as high performance catalyst supports and electrodes for PEM fuel cells
Carbon
Simultaneous sulfonation and reduction of graphene oxide as highly efficient supports for metal nanocatalysts
Carbon
Sonoelectrochemical (20 kHz) production of platinum nanoparticles from aqueous solutions
Electrochim. Acta
A novel method for preparing PEMFC electrodes by the ultrasonic and sonoelectrochemical techniques
Electrochem. Commun.
A novel method for preparing proton exchange membrane fuel cell electrodes by the ultrasonic-spray technique
J. Power Sources
Platinum sonoelectrodeposition on glassy carbon and gas diffusion layer electrodes
Int. J. Hydr. Energy
Support materials for PEMFC and DMFC electrocatalysts – a review
J. Power Sources
Argirusis. Sonoelectrochemical one-pot synthesis of Pt–Carbon black nanocomposite PEMFC electrocatalyst
Ultrason. Sonochem.
Sonochemical and sonoelectrochemical production of hydrogen
Ultrason. Sonochem.
A fast method to prepare Pd-Co nanostructures decorated on graphene as excellent electrocatalyst toward formic acid oxidation
J. Alloy Compd.
Three-dimensional assembly of building blocks for the fabrication of Pd aerogel as a high performance electrocatalyst toward ethanol oxidation
Electrochim. Acta
One-pot synthesis of ultrasmall Pt-Ag nanoparticles decorated on graphene as a high-performance catalyst toward methanol oxidation
Int. J. Hydr. Energy
Hollow raspberry-like PdAg alloy nanospheres: high electrocatalytic activity for ethanol oxidation in alkaline media
J. Power Sources
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