Heterogeneous Ir3Sn–CeO2/C as alternative Pt-free electrocatalysts for ethanol oxidation in acidic media

https://doi.org/10.1016/j.ijhydene.2016.12.139Get rights and content

Highlights

  • Heterogeneous Ir3Sn–CeO2/C is prepared as alternative Pt-free electrocatalyst.

  • Strong synergistic effect among Ir, Sn and CeO2 is related to the high performance.

  • Each constitutive component of this catalyst is stable in acidic conditions.

Abstract

For reducing the Pt usage and driving down the cost of fuel cells, it is urgent to develop alternative Pt-free catalysts with high catalytic performance. In this study, an Ir3Sn–CeO2/C heterogeneous catalyst is designed as low-price, alternative Pt-free electrocatalyst towards ethanol oxidation reaction (EOR) in acidic conditions. Owing to the strong synergistic effect among Ir, Sn and CeO2 components, Ir3Sn–CeO2/C heterogeneous catalyst exhibits higher catalytic activity and stability for EOR in comparison with commercial Pt/C, as-prepared Ir/C and Ir3Sn/C. Additionally, kinetics and mechanisms of EOR are also investigated. It proves that ethanol electrooxidation on Ir3Sn–CeO2/C catalyst is a diffusion controlled irreversible process. Meanwhile, the H2SO4 and ethanol concentrations can affect the EOR activity. All results demonstrate Ir3Sn–CeO2/C heterogeneous catalyst is a promising Pt-free choice for EOR.

Introduction

Over the last decade, the global energy crisis and environmental issues stimulate much attention on new renewable energy storage and conversion. Particularly, direct alcohol fuel cells (DAFCs) have triggered increased interest, mainly due to their potential applications in electric vehicles and portable electronic apparatus [1], [2], [3]. However, its practical feasibility is still restricted by the high cost and low stability of Pt-based catalysts [4], [5]. For reducing the Pt usage and driving down the price of fuel cells, it is urgent to develop alternative Pt-free catalyst with high catalytic performance [6], [7], [8]. Various Pd and Pd-based catalysts have been recognized as promising substitutes to Pt in alkaline media for anode reaction [7], [9], [10]. Although fuel cells in acidic media have numerous advantages, such as good proton conductivity and mechanical stability [11], the development of high-efficiency Pt-free electrocatalysts for ethanol oxidation reaction (EOR) in acidic media still remains a huge challenge.

One effective strategy to design advanced catalysts is the use of multicomponent systems, which contains more than two different nanoscale components [12]. The heterogeneous catalysts exhibit the intrinsic property of constitutive components as well as the synergistic interaction between them [13]. With this interaction, heterogeneous catalysts exhibit novel physical and chemical characters, which could lead to the development of highly active Pt-free electrocatalysts for fuel cells. As one of the most stable materials in acidic conditions, Ir shows good performance in some catalytic reactions due to its low cost, high resistance to COads, excellent oxygen evolution and good oxygen reduction [14], [15], [16]. However, only few studies have been reported about the Ir-based catalysts as anode electrocatalysts for EOR. In 2007, Lei et al. investigated the Ir3Sn/C catalyst towards EOR in acidic media for the first time, strongly demonstrating the significant potential of Ir metal as an alternative Pt-free electrocatalyst in anode reaction. Then, in the pursuit of more efficient Ir-based catalysts for DAFCs, a highly active Ir/Ir–Sn/SnO2 heterogeneous catalyst was found for EOR by Du's group [15]. It indicated that both the IrSn alloy and SnO2 on the surface could play an important role in catalytic performance. This research is very encouraging to design novel Ir-based heterogeneous catalysts by combining the alloy and oxide. Questions, most of the metal oxides are easy to dissolve in extreme conditions, and then, would affect the catalytic activity and stability [17].

Recently, CeO2 has been received remarkable attention as a promoter to improve the catalytic performance, due to its anticorrosion ability in acidic media, oxygen vacancy defects and high oxygen-storage capacity [18], [19]. These features make the CeO2-metal hybrid structure particularly useful for some reactions. In the last years, several literature have been demonstrated that CeO2 can increase the dispersion of active metal and obtain synergistic effect between noble metal nanoparticles and CeO2 [20], [21], [22], thus are promising to achieve a high catalytic performance. In this respect, it is supposed that combining CeO2 and Ir-based alloy into a heterogeneous structure should possess high electrochemical performance for EOR. Herein, a novel Ir3Sn–CeO2/C heterogeneous catalyst as alternative Pt-free electrocatalyst is designed, characterized and tested for EOR. The electrochemical results prove that, relative to commercial Pt/C, as-prepared Ir3Sn/C and Ir/C catalysts, Ir3Sn–CeO2/C heterogeneous catalyst exhibits high EOR activity and good stability in acidic conditions. In addition, the effects of concentrations and scan rates on Ir-based catalyst are performed for the first time.

Section snippets

Preparation of CeO2/C precursor

CeO2/C was prepared using a traditional precipitation procedure. According to the pre-calculated amount, Ce(NO3)3·6H2O aqueous solution was mixed with Vulcan XC-72R carbon black. Then, the dilute NH3·H2O solution was added dropwise to the obtained solution under steady stirring, until the value of pH reached 10. Next, the mixture was stirred for 3 h. After that, the suspension was centrifuged several times and washed with ultrapure water. Then, the sample was dried in a vacuum oven (for 6 h at

Physical characterization

XRD is employed to obtain structural information of the CeO2/C, Ir3Sn–CeO2/C, Ir3Sn/C, Ir/C and Pt/C (Fig. 1). For CeO2/C precursor, diffraction peaks at 28.6°, 33.1°, 47.5°, 56.5°,76.7°, 79.4°and 88.6° are ascribed to the (111), (200), (220), (311), (331), (420) and (422) characteristic crystalline planes of the fluorite structure CeO2. This indicates the successful preparation of CeO2/C by the precipitation method [10]. For Pt/C catalyst, the broad peak at 25° corresponds to the carbon (200),

Conclusions

In conclusion, a novel Ir3Sn–CeO2/C heterogeneous catalyst was prepared, characterized and tested as alternative Pt-free electrocatalyst for EOR in acidic media. Electrochemical measurements prove that the heterogeneous Ir3Sn–CeO2/C catalyst exhibits high EOR activity and good stability in comparison with the Pt/C, Ir3Sn/C and Ir/C catalysts. This high performance can be explained by the strong synergistic effect among Ir, Sn and CeO2. Besides, the kinetics of Ir3Sn–CeO2/C catalyst towards EOR

Acknowledgement

We thank to the National Natural Science Foundation of China (21561019), the program of Changjiang Scholars and Innovative Research Team in University (IRT_15R56) and the Innovative Research Team of Gansu Province (1606RJIA324).

References (47)

  • S.S. Li et al.

    Rapid room-temperature synthesis of Pd nanodendrites on reduced graphene oxide for catalytic oxidation of ethylene glycol and glycerol

    Int J Hydrogen Energy

    (2014)
  • G. Wu et al.

    Effect of electrochemical polarization of PtRu/C catalysts on methanol electrooxidation

    Electrochim Acta

    (2004)
  • C.C. Chen et al.

    A binary palladium-bismuth nanocatalyst with high activity and stability for alkaline glucose electrooxidation

    J Power Sources

    (2015)
  • L. Ma et al.

    Comparison of ethanol electro-oxidation on Pt/C and Pd/C catalysts in alkaline media

    Int J Hydrogen Energy

    (2012)
  • T. Ramulifho et al.

    Fast microwave-assisted solvothermal synthesis of metal nanoparticles (Pd, Ni, Sn) supported on sulfonated MWCNTs: Pd-based bimetallic catalysts for ethanol oxidation in alkaline medium

    Electrochim Acta

    (2012)
  • E. Antolini et al.

    Effect of synthesis method and structural characteristics of Pt-Sn fuel cell catalysts on the electro-oxidation of CH3OH and CH3CH2OH in acid medium

    Catal Today

    (2011)
  • A. Brouzgou et al.

    Glucose electrooxidation over PdxRh/C electrocatalysts in alkaline medium

    Appl Catal B Environ

    (2014)
  • W. Wang et al.

    Fe-Co hybrid oxides promoted Pd electrocatalysts with enhanced catalytic performance for ethylene glycol oxidation

    Int J Hydrogen Energy

    (2015)
  • R.S. Amin et al.

    Electrocatalytic activity of nanostructured Ni and Pd-Ni on Vulcan XC-72R carbon black for methanol oxidation in alkaline medium

    Int J Hydrogen Energy

    (2014)
  • D. Chai et al.

    A facile precipitation procedure for synthesis of binary Sn-Co oxide promoting Pd catalyst towards glucose electrooxidation

    Electrochim Acta

    (2016)
  • Y. Song et al.

    Nanoporous Pd/TiO2 composites prepared by one-step dealloying and their electrocatalytic performance for methanol/ethanol oxidation

    Mater Chem Phys

    (2015)
  • W. Wang et al.

    Pd3Ni nanoparticles combines carbonized 1,10-phenanthroline modified carbon support: a highly efficient electrocatalyst for enhanced methanol oxidation

    Int J Hydrogen Energy

    (2015)
  • L.X. Ding et al.

    Porous Pt-Ni-P composite nanotube arrays: highly electroactive and durable catalysts for methanol electrooxidation

    J Am Chem Soc

    (2012)
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