Direct Alcohol Fuel Cells Research Articles

Bio-Based Graphene Sheet/Copolymer Composite as Supporting Material for Nanocatalysts towards Electrochemical Studies and Direct Alkaline Alcohol Fuel Cells

In this work, graphene carbon sheets (BGS) were prepared from writing paper and lemon peel, and its polymer composite has a higher surface area compared with the existing Vulcan carbon. Further, the use of lead as a promoter for the oxidation of alcohol and CO on platinum-supported poly(amine-terminated cyclophosphazene-co-cyclophosphazene)-biobased graphene sheet (Poly(AFCP-co-CP)-BGS) composite was demonstrated. The size, phase morphology, and distribution of metal nanoparticles on Poly(AFCP-co-CP)-BGS composite as well as the formation of composite based catalysts were confirmed from TEM, XRD, and FTIR studies. The catalytic activity and stability of the prepared catalysts were tested and compared to methanol, ethylene glycol, glycerol, and CO in 0.5 M KOH solution. The results conclude that the lead-doped Pt/Poly(AFCP-co-CP)-BGS catalyst shows higher oxidation current with respect to onset potential and lower I f / I r ratio for alcohol as well as CO oxidation. In addition, Pt-Pb/Poly(AFCP-co-CP)-BGS catalyst was checked for direct alkaline fuel cells and proved as a potent anode catalyst in alkaline medium for real-time fuel battery applications. In addition, Poly(AFCP-co-CP)-BGS composite also promotes the catalytic reaction compared to Poly(AFCP-co-CP) and BGS supports as noticed from methanol oxidation in alkaline medium. The surface area of the prepared supporting material is 750.72 m2g-1, which is higher than the activated carbon (250.12m2g-1). So, the prepared Poly(AFCP-co-CP)-BGS composite is a potent support for metal deposition, electrooxidation, and single stack fuel cell constructions.

Effect of Sn Doping on Pd Electro-Catalysts for Enhanced Electro-Catalytic Activity towards Methanol and Ethanol Electro-Oxidation in Direct Alcohol Fuel Cells.

Carbon nano-onions (CNOs) were successfully synthesized by employing the flame pyrolysis (FP) method, using flaxseed oil as a carbon source. The alcohol reduction method was used to prepare Pd/CNOs and Pd-Sn/CNOs electro-catalysts, with ethylene glycol as the solvent and reduction agent. The metal-nanoparticles were supported on the CNO surface without adjusting the pH of the solution. High-resolution transmission electron microscopy (HRTEM) images reveal CNOs with concentric graphite ring morphology, and also PdSn nanoparticles supported on the CNOs. X-ray diffractometry (XRD) patterns confirm that CNOs are amorphous and show the characteristic diffraction peaks of Pd. There is a shifting of Pd diffraction peaks to lower angles upon the addition of Sn compared to Pd/CNOs. X-ray photoelectron spectroscopy (XPS) results also confirm the doping of Pd with Sn to form a PdSn alloy. Fourier transform infrared spectroscopy (FTIR) displays oxygen, hydroxyl, carboxyl, and carbonyl, which facilitates the dispersion of Pd and Sn nanoparticles. Raman spectrum displays two prominent peaks of carbonaceous materials which correspond to the D and G bands. The Pd-Sn/CNOs electro-catalyst demonstrates improved electro-oxidation of methanol and ethanol performance compared to Pd/CNOs and commercial Pd/C electro-catalysts under alkaline conditions.

Synthesis of PtRu alloy nanofireworks as effective catalysts toward glycerol electro-oxidation in alkaline media

Electro-oxidation of glycerol is a key anodic reaction in direct alcohol fuel cell (DAFCs). Exploring the cost-effective nanocatalysts for glycerol oxidation reaction (GOR) is very important for the development of DAFC, but it is still challenging. In this paper, nanofirework-like PtRu alloy catalyst was successfully synthesized and used for GOR in alkaline medium. Thanks to the unique nanofirework-like structure and synergetic effects, the activity and stability of the as-prepared PtRu alloy nanofireworks (NFs) toward GOR were significantly improved relative to Pt NFs. In particular, the peak current density of GOR catalyzed by the optimized Pt1Ru3 NFs catalyst reached 2412.0 mA mg−1, surpassing that of commercial Pt/C catalyst. This work has important guidance for the design of advanced anode electrocatalysts for fuel cells.

Electrochemical synthesis of PdNPs@MnO2-PPy nanocomposite and its electrocatalytic application towards glycerol oxidation

Direct alcohol fuel cell (DAFC) exhibits several unique features, such as the high tendency to energy conversion, low cost, abundance of fuel, less hazardous to the environment, and simple handling, and has diverse applications in microelectronics. In this context, the present study describes a facile and straightforward method to fabricate the PdNPs@MnO2-PPy catalyst as an anode electrode for the oxidation of glycerol in an alkaline medium. Herein, the PdNPs@MnO2-PPy catalyst was developed through a two-step electrochemical deposition technique. The as-prepared catalyst was characterized by physicochemical and electrochemical techniques. Electrochemical measurements revealed that the PdNPs@MnO2-PPy catalyst exhibits excellent catalytic properties, anti-poisoning resistance to intermediates, and durability than that of already reported catalysts and Pd/C. These unique advantages of the proposed catalyst have been achieved due to PdNPs, strong synergistic effects, and MnO2-PPy support providing superior electron transfer. The proposed electrocatalyst exhibits high current density (240.2mA/cm2), large electrochemically active surface area (302.1 m2g−1), and good long-term stability (450 cycles). Further, the electrocatalysis mechanism of glycerol oxidation was studied. The design, synthesis, and excellent catalytic response of PdNPs@MnO2-PPy offer a conception and promising potential to be used as an anode electrode in direct alcohol fuel cells.

Platinum group metal-free Fe-based (Fe N C) oxygen reduction electrocatalysts for direct alcohol fuel cells

In direct alcohol fuel cells (DAFCs), the oxidation of alcohols happens at the expenses of the oxygen reduction reaction at the cathode. DAFCs' cathodes use a significant amount of platinum that is an expensive critical raw material. Moreover, platinum oxidizes alcohols, a fact that combined with alcohol crossover, decreases significantly the performance of the cells. The use of Fe-based (FeNC) platinum group metal–free (PGM-free) cathodes is a convenient strategy to overcome these limitations. This review analyzes the application of PGM-free cathodes to DAFCs. The discussion focuses on acidic systems and covers the following subjects: (i) the breakdown of DAFC potential in its components, (ii) the analysis of the advantages from the use of the PGM-free cathode, and (iii) a review of the performance and durability of DAFCs. The review closes with a view of the authors of the future perspective for the research.

Comparison of Pt and Pd anode catalysts supported on nanocrystalline Ru–SnO2 for ethanol oxidation in fuel cell applications

The article presents promising catalysts, applicable for direct alcohol fuel cells (DAFC) for portable and mobile applications. The goal of this work is development of Pt and Pd catalysts deposited on interactive nanocrystalline Ru doped SnO2 support with improved performance. The structure and the morphology of the prepared metal-oxide catalyst support and Pt and Pd based catalysts were examined using XRPD, SEM/EDX and TEM techniques. Electrocatalytic activities of the prepared Pt or Pd based catalysts were evaluated in both alkaline and acidic conditions. The ethanol oxidation reaction (EOR) was studied using conventional electrochemical techniques. The interactive nature of the novel Ru doped SnO2 catalyst support was confirmed, resulting in the enhancement of the EOR kinetics, in comparison to commercially available catalysts. New and simplified synthetic route applied for preparation of interactive catalyst support was presented with the aim to enable easy scale-up of the catalyst production process. Obtained results on the novel catalysts promise great potential in improving the performance and durability of the DAFC.

Sub-Monolayer YOx /MoOx on Ultrathin Pt Nanowires Boosts Alcohol Oxidation Electrocatalysis.

A crucial issue restricting the application of direct alcohol fuel cells (DAFCs) is the low activity of Pt-based electrocatalysts for alcohol oxidation reaction caused by the reaction intermediate (CO*) poisoning. Herein, a new strategy is demonstrated for making a class of sub-monolayer YOx /MoOx -surface co-decorated ultrathin platinum nanowires (YOx /MoOx -Pt NWs) to effectively eliminate the CO poisoning for enhancing methanol oxidation electrocatalysis. By adjusting the amounts of YOx and MoOx decorated on the surface of ultrathin Pt NWs, the optimized 22% YOx /MoOx -Pt NWs achieve a high specific activity of 3.35mA cm-2 and a mass activity of 2.10 A mgPt -1 , as well as the enhanced stability. In situ Fourier transform infrared (FTIR) spectroscopy and CO stripping studies confirm the contribution of YOx and MoOx to anti-CO poisoning ability of the NWs. Density functional theory (DFT) calculations further reveal that the surface Y and Mo atoms with oxidation states allow COOH* to bind the surface through both the carbon and oxygen atoms, which can lower the free energy barriers for the oxidation of CO* into COOH*. The optimal NWs also show the superior activities toward the electro-oxidation of ethanol, ethylene glycol, and glycerol.

Pd nanoparticles on self-doping-defects mesoporous carbon supports for highly active ethanol oxidation and ethylene glycol oxidation

The high activity electrocatalysts with low cost are crucial for large-scale direct alcohol fuel cells (DAFCs) applications. In this study, the “self-doping-defects” mesoporous carbon (SDMC) as support of uniformly-dispersed Pd nanoparticles (Pd/SDMC) was prepared for high active electrooxidation by a simple route without additional surfactant and acid treatment. According to the mutually corroborated experimental and theoretical calculation results, our route can significantly increase the carbon defect, which is conducive to the anchoring and uniform distribution of Pd nanoparticles. Meanwhile, the uniquely and hierarchically mesoporous nanostructure of SDMC provides abundant pathways for mass transport in the electrooxidation reaction. Benefitting from the above advantages, Pd/SDMC exhibits superior activity than commercial Pd/C and previously reported carbon-based electrocatalysts. The mass activities and specific activities of Pd/SDMC toward ethanol oxidation reaction (EOR) are 3404.3 mA mg−1, 4.48 mA cm−2, respectively. The mass activities and specific activities of Pd/SDMC for ethylene glycol oxidation reaction (EGOR) are 4002 mA mg−1, 5.26 mA cm−2, respectively. We believe that the facile strategy to synthesis mesoporous carbon with “self-doping” defects would promote large-scale DAFCs applications in the future.

Interface engineering of metal nanomaterials enhance the electrocatalytic water splitting and fuel cell performance

AbstractWe conclude this review with a perspective of interface engineering strategy for enhancing the activity of metal catalysts for electrocatalytic water splitting and direct alcohol fuel cells (DAFCs). The organic ligands could modify the surface of metal nanostructures, and also could affect the electronic structure of metals. Due to the specific physical and chemical properties of organic ligands, the metal nanostructures exhibit super catalytic selectivity to some reaction precursors. This minireview focuses on evaluating the catalytic mechanisms for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), alcohol oxygen reaction (AOR), and oxygen reduction reaction (ORR), which are the main reactions for water splitting and DAFCs, respectively, which are driven by interface engineering. This new strategy provides an approach for the design and synthesis of nanostructures modifying by organic ligands, providing a reasonable outlook of their extensive application in chemical energy conversion and storage, and selective fuel production.

Primary Vs. Secondary Alcohols Electrooxidation: Mechanistic Insights

Direct Alcohol Fuel Cells (DAFCs), mostly based on methanol or ethanol, have been in the spotlight in the past, due to alcohols’ high and easy availability, low cost, liquid form, low temperature operation and comparable theoretical mass energy densities in comparison with Hydrogen Fuel Cells.[1] However, 2-propanol fuel cells can be preferred for coupling with Liquid Organic Hydrogen Carriers (LOHCs), by creating a closed loop where 2-propanol is oxidized in a fuel cell to acetone and the latter is hydrogenated back to 2-propanol by the catalytic transfer hydrogenation reaction with a hydrogen-rich LOHC molecule.[2] Here, we characterize the products of 2-propanol oxidation on Pt and PtRu and find that the reaction is selective to acetone on both surfaces. Interestingly, the addition of ruthenium gives rise to an early oxidation peak close to the reversible potential, which is not present in 1-propanol oxidation.[3] The early onset of the 2-propanol oxidation leads to significantly larger Open Circuit Voltages (OCVs) for fuel cells based on 2-propanol compared to 1-propanol, when PtRu is used as the anode. By studying the oxidation of larger (C4 and C5) alcohols, we find that this is a unique characteristic of secondary alcohols on platinum-ruthenium bimetallic catalysts. Using a combination of Rotating Disc Electrode (RDE) measurements, Density Functional Theory (DFT) calculations and real-time product analysis with Electrochemical Real-Time Mass Spectrometry (EC-RTMS) we conclude that the unique feature of secondary alcohols stems from the difficulty in breaking their C-C bond, which prevents their dissociative adsorption at low potential and enables the optimal adsorption on platinum-ruthenium ensemble sites.[4] Acknowledgements I.M.-G, P.K, K.J.J.M. and I.K. acknowledge financial support by the Bavarian Ministry of Economic Affairs, Regional Development and Energy.F.C.-V. acknowledges funding from Spanish MICIUN RTI2018-095460-B-I00, Ramón y Cajal RyC-2015-18996 and María de Maeztu MDM-2017-0767 grants and partly by Generalitat de Catalunya 2017SGR13. O.P. thanks the Spanish MICIUN for a PhD grant (PRE2018-083811). We thank Red Española de Supercomputación (RES) for supercomputing time at SCAYLE (projects QS-2019-3-0018, QS-2019-2-0023, and QCM-2019-1-0034), MareNostrum (project QS-2020-1-0012), and CENITS (project QS-2020-2-0021). The use of supercomputing facilities at SURFsara was sponsored by NWO Physical Sciences, with financial support by NWO.

Void-Enriched and Highly Strained Porous Au–Ag Nanoalloy as a Bifunctional Electro-Catalyst in Alkaline Direct Alcohol Fuel Cell

Void-Enriched and Highly Strained Porous Au–Ag Nanoalloy as a Bifunctional Electro-Catalyst in Alkaline Direct Alcohol Fuel Cell

One-pot synthesis of rugged PdRu nanosheets as the efficient catalysts for polyalcohol electrooxidation

Recently, intensive attention has been attracted to the two-dimensional metal nanosheets, owing to their excellent electrocatalytic performance for direct alcohol fuel cells (DAFCs). Herein, PdRu nanosheets have been synthesized successfully by a facile one-pot method. The rugged nanosheet structure provided plentiful surface active sites to enhance the electrocatalytic activity. Moreover, benefiting from the synergistic effect and improved electronic structure, PdRu NSs exhibited splendid electrocatalytic performance in ethylene glycol oxidation reaction (EGOR) and glycerol oxidation reaction (GOR). Specifically, the mass activity of PdRu NSs was 1.72 and 3.69 times over those of Pd NSs and Pd/C catalysts in EGOR. Moreover, PdRu NSs displayed the largest mass activity in GOR, 1.48 and 2.47 times as large as Pd NSs and Pd/C catalysts. The results of stability tests demonstrated that the durability of PdRu NSs was the highest among the obtained catalysts. This work plays a directive role on the in-depth engineering on Pd-based catalysts with nanosheet architectures.

A novel electrodeposited poly(melamine)-palladium nanohybrid catalyst on GCE: Prosperous multi-functional electrode towards methanol and ethanol oxidation

Herein, a novel Poly (melamine) have been successively electrodeposited on glassy carbon electrode and decorated by Pd nanoparticles (Pd NPs) subsequently to fabricate Poly (melamine) – Pd nanocomposite. Structural geometry, morphological view, and elemental composition analysis were ensured by X-ray diffractogram, scanning electron microscope, and X-ray photoelectron spectroscopy. The electrodeposited Poly (melamine) (PME) material depicts an interconnected nano rod (50 nm) morphology leads to a nano exploder (~150 nm) arrangement. Spherical shaped Pd decorated PME morphology was obtained for GC\\PME-Pd NPs composite (150 nm). The electrocatalytic activity of the fabricated anode electrocatalyst was examined by cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry methods. The modified GC\\PME-Pd NPs composite electrode validates superior electrocatalytic behaviour towards methanol and ethanol oxidation in alkaline background. Besides, the electrochemical surface area and electrocatalytic behaviour make it a greater anode catalyst towards methanol and ethanol oxidation. The synergic effects amid the Poly (melamine)-Pd NPs composite enhances the catalytic activity, mechanical stability on the electrocatalysis of methanol and ethanol oxidation reaction superior than modified Poly (melamine) electrode. Hence, the fabricated anode electrocatalyst is proficient to get realistic approach towards the progression in the direct alcohol (methanol and ethanol) oxidation reaction in direct alcohol fuel cells (DAFCs) applications.

Effect of Anode Material on Electrochemical Oxidation of Low Molecular Weight Alcohols-A Review.

The growing climate crisis inspires one of the greatest challenges of the 21st century—developing novel power sources. One of the concepts that offer clean, non-fossil electricity production is fuel cells, especially when the role of fuel is played by simple organic molecules, such as low molecular weight alcohols. The greatest drawback of this technology is the lack of electrocatalytic materials that would enhance reaction kinetics and good stability under process conditions. Currently, electrodes for direct alcohol fuel cells (DAFCs) are mainly based on platinum, which not only provides a poor reaction rate but also readily deactivates because of poisoning by reaction products. Because of these disadvantages, many researchers have focused on developing novel electrode materials with electrocatalytic properties towards the oxidation of simple alcohols, such as methanol, ethanol, ethylene glycol or propanol. This paper presents the development of electrode materials and addresses future challenges that still need to be overcome before direct alcohol fuel cells can be commercialized.

Platinum-Based Electrocatalysts for Direct Alcohol Fuel Cells: Enhanced Performances toward Alcohol Oxidation Reactions.

In the past few decades, Pt-based electrocatalysts have attracted great interests due to their high catalytic performances toward the direct alcohol fuel cell (DAFC). However, the high cost, poor stability, and the scarcity of Pt have markedly hindered their large-scale utilization in commerce. Therefore, enhancing the activity and durability of Pt-based electrocatalysts, reducing the Pt amount and thus the cost of DAFC have become the keys for their practical applications. In this minireview, we summarized some basic concepts to evaluate the catalytic performances in electrocatalytic alcohol oxidation reaction (AOR) including electrochemical active surface area, activity and stability, the effective approaches for boosting the catalytic AOR performance involving size decrease, structure and morphology modulation, composition effect, catalyst supports, and assistance under other external energies. Furthermore, we also presented the remaining challenges of the Pt-based electrocatalysts to achieve the fabrication of a real DAFC.

A new method for synthesizing high performance few-layer graphene supported Pt electrocatalysts in methanol and ethanol oxidation

Here, new catalysts for application in the Direct Alcohol Fuel Cells (DMFC and DEFC), comprising of 1–8 wt% Pt dispersed on few layer graphene (FLG), are successfully synthesized, by means of a rapid, simple, inexpensive and environmentally friendly one-pot method. The mass activity of the PFG3 catalyst for methanol, in acid and alkaline media, was 25,243 mA mgPt−1 and 112,882 mA mgPt−1, respectively; for ethanol, in acid and alkaline media, was 25,000 mA mgPt−1 and 65,272 mA mgPt−1, respectively. These values were from tens to hundreds of times higher than those recently published for graphene-support Pt electrocatalysts. Our results suggest that the one-pot synthesis method result in simultaneous exfoliation, reduction and deposition during microwave irradiation in a very short time for producing catalysts with extremely high electrochemical performance, which may be effective alternative method for synthesis of electrocatalysts for DMFC and DEFC.

Direct alcohol fuel cells: Assessment of the fuel's safety and health aspects

Fuel cell (FC) is simply a device that directly converts the chemical energy of fuel into electrical energy through electrochemical oxidation. Hence, FC inherently exhibits a low-temperature and high-energy conversion efficiency. Direct alcohol fuel cells (DAFCs) overcome the storage, handling, and safety challenges typically associated with gaseous fuels such as hydrogen. Most of the research and development work in DAFC is focusing on maximizing its performance by varying fuel concentration, operating conditions, and electrocatalysts used. However, less attention is being given to the health and safety aspects associated with these fuels and operating conditions. Most of these fuels are known to be highly flammable, toxic, and become even more hazardous at elevated temperatures. The present work performs a systematic assessment of the safety and health aspects of the widely used fuels for DAFCs, namely methanol, ethanol, ethylene glycol, and glycerol. The safety assessment is considering the flammability characteristics, along with other safe operation aspects. While the health assessment considers the toxicity of fuel and its reaction byproducts to human and aquatic life. The evaluation has provided an envelope of conditions at which the FC operation would be considered “safer” by applying basic principles of inherent safety, i.e., minimizing, substituting, moderating, and simplifying.

High Performance Pt Nanocatalysts for the Oxidation of Methanol and Ethanol in Acid Media by Effect of Functionalizing Carbon Supports with Ru Organometallic Compounds

The Intermittent Microwave Heating (IMH) assisted polyol method was used to disperse Pt nanoparticles on Vulcan XC-72 (C) and reduced Graphene Oxide (rGO) functionalized with [(η 6-C6H5OCH2CH2OH)RuCl2]2 (Ru-dim) and [(η 6-C6H4(CHMe2)Me)RuCl2]2 (Ru-cym). The nanocatalysts were labeled as Pt/CRu-dim, Pt/CRu-cym, Pt/rGORu-dim and Pt/rGORu-cym. Their catalytic activity was evaluated for the Methanol (MOR) and Ethanol Oxidation Reactions (EOR). 1H and APT 13C NMR characterization showed the coordination of arene ligands with ruthenium atoms, supporting the formation of Ru-dim and Ru-cym. Raman spectroscopy indicated that C and rGO preserve their graphitic band structure after functionalization. Functionalization of the supports resulted in the development of several surface chemical groups. The electrochemical characterization showed that: i) Pt/CRu-dim was the nanocatalyst with the highest catalytic activity for the MOR, demonstrating also a high performance for the EOR; ii) Pt/rGORu-cym showed a good electrocatalytic behavior for both reactions at more negative potentials, nevertheless delivering lower current densities (j). In terms of the organic molecule, higher j values have been obtained from the MOR, compared to the EOR. The results showed that these nanocatalysts can be considered as anode materials in Direct Alcohol Fuel Cells applications.

Ultrafine Pt stabilized on Ti3C2Tx/reduced graphene oxide nanocomposites for alcohol oxidation reaction (AOR)

Three-dimensional platinum/Ti3C2Tx-reduced graphene oxide was prepared by solvothermal method. The morphology, microstructure and composition of the catalyst were examined. The synthesized Pt/Ti3C2Tx-rGO exhibits superior electrocatalytic activity, CO tolerance and long-term stability towards alcohol oxidation reaction. This work demonstrates for the first time that Pt/Ti3C2Tx-rGO can be used as an effective anode catalyst for direct alcohol fuel cell (DAFC).

Photo-responsive metal/semiconductor hybrid nanostructure: A promising electrocatalyst for solar light enhanced fuel cell reaction

Direct alcohol fuel cells (DAFCs) have received wide attention as a new type of clean energy device because of their high energy conversion efficiency, portability, non-toxicity and pollution-free. Anode catalysts are the key factors affecting the performance of DAFCs. Recently studies show that using the optical activity of semiconductor materials as the carriers of traditional precious metal electrocatalysts, under the illumination of light sources, can greatly improve the electrocatalytic activity and stability of electrodes. In this review, the research progress of photo-responsive metal/semiconductor hybrids as the electrocatalysts for DAFCs in recent years is summarized, including: (1) Mechanism and advantages of photo-assistant electrochemical alcohol oxidation reaction, (2) metal/semiconductor electrocatalyst for the different type of fuel cell reactions, (3) different kind of metals in photo-responsive metal/semiconductor hybrid nanostructure, (4) the personal prospects of the photo-responsive metal/semiconductor electrode for future application in DAFCs.