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Article

Performance Improvement in Direct Methanol Fuel Cells by Using CaTiO3-δ Additive at the Cathode

by
Lucia Mazzapioda
1,
Carmelo Lo Vecchio
2,
Antonino Salvatore Aricò
2,
Maria Assunta Navarra
1,2,* and
Vincenzo Baglio
2,*
1
Department of Chemistry, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
2
CNR-ITAE, Istituto di Tecnologie Avanzate per l’Energia “Nicola Giordano”, Via Salita S. Lucia 5, 98126 Messina, Italy
*
Authors to whom correspondence should be addressed.
Catalysts 2019, 9(12), 1017; https://doi.org/10.3390/catal9121017
Submission received: 8 November 2019 / Revised: 27 November 2019 / Accepted: 28 November 2019 / Published: 2 December 2019
(This article belongs to the Special Issue Electro-Catalysts for Energy Conversion and Storage Devices)
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Abstract

:
A non-stoichiometric calcium titanate CaTiO3-δ (CTO) was synthesized and used as oxygen reduction reaction co-catalyst (together with Pt/C) in direct methanol fuel cells (DMFCs). A membrane-electrode assembly (MEA), equipped with a composite cathode formulation (Pt/C:CTO1:1), was investigated in DMFC, using a 2 M methanol solution at the anode and oxygen at the cathode, and compared with an MEA equipped with a benchmark Pt/C cathode catalyst. It appears that the presence of the CTO additive promotes the oxygen reduction reaction (ORR) due to the presence of oxygen vacancies as available active sites for oxygen adsorption in the lattice. The increase in power density obtained with the CTO-based electrode, compared with the benchmark Pt/C, was more than 40% at 90 °C, reaching a maximum power density close to 120 mW cm−2, which is one of the highest values reported in the literature under similar operating conditions.

1. Introduction

Direct methanol fuel cells (DMFCs) are electrochemical devices envisaged as convenient power sources for portable applications since they have high energy density, good energy conversion efficiency, and low environmental impact [1,2]. However, there are significant drawbacks to overcome in order to allow DMFCs commercialization; i.e., sluggish kinetics of methanol oxidation (MOR) and oxygen reduction (ORR) reactions, methanol cross-over through the polymer electrolyte membrane, and the high cost of the complete device [3,4,5]. In particular, the use of noble metal catalysts, both at the anode and cathode, significantly affects the cost of the DMFC [5]. Pt-based nanoparticles are the benchmark catalysts for MOR and ORR, but at the cathode compartment, they promote also methanol oxidation, resulting in mixed potential, which produces a decrease of the overall cell voltage [2].
Several approaches of the last decade were explored with the aim to reduce cost and improve ORR in the presence of permeated methanol [6,7,8,9,10,11,12]. Pt-alloys exhibit enhanced electrocatalytic activity for the ORR compared to Pt alone [13,14], due to both electronic factors (i.e., higher level of Pt d-band vacancy) and geometric effects (i.e., optimized Pt–Pt interatomic distance). In fact, a lattice contraction is realized, due to alloying, resulting in a more favorable Pt–Pt distance for the adsorption of O2 [15,16]. Furthermore, alloying Pt with other transition metals can reduce the adsorption of alcohols on the cathode surface thanks to a dilution effect [17,18,19,20,21,22], since at least three adjacent Pt sites are needed for the dissociative adsorption of methanol [2,23].
An interesting approach to increase the performance of Pt catalyst is the addition of fillers that, thanks to their tunable surface properties, can act as Pt promoters. Several metal oxides have been investigated and studied as additives (or also as a support) for Pt-based catalysts such as SnO2 [24], TiO2 [25,26], ZrO2 [27], IrO2 [28] showing an enhancement in terms of activity and durability of the catalyst. Among these materials, TiO2 has attracted a major interest because of its stability in acidic fuel cell environment, as well as the features of being inexpensive, safe (not toxic), and abundant in nature [29,30]. Nevertheless, TiO2 material cannot be considered as a suitable catalyst support because unmodified and bulk titanium oxides present a low electrical conductivity [31].
According to the most recent literature, perovskite oxides are playing an important role as oxygen electrocatalysts especially in alkaline solutions, due to their favorable catalytic activity toward both the ORR and the oxygen evolution reaction (OER) [32,33]. Their success consists of their versatile and flexible structure (ABO3) that can accommodate different dopant agents, such as transition metal ions (Fe, Ni, Co, Sr) on both the A and the B cations position, giving rise to a change in the band structure and to the formation of oxygen vacancies. These structural changes can modify the electrical properties of the material, influencing the catalytic activity [34]. The optimal ORR catalyst should possess moderate surface-oxygen interaction energy, allowing for the right balance between the adsorption and desorption of the reactants and the intermediates [35,36]. Consequently, a good promoter of ORR must to be able to facilitate the adsorption of oxygen and to establish a synergistic catalytic effect with the Pt catalyst.
Our idea, considering the above-mentioned requirements, has been to improve the properties of titanium-based oxides taking advantage from the perovskite structure. Here, we propose a non-stoichiometric calcium titanate CaTiO3-δ (CTO) as an ORR co-catalyst for application in direct methanol fuel cells. This material, prepared by using a solvo-thermal method, has been recently investigated as a promoter of Pt/C catalysts for the ORR in rotating disk electrode (RDE), showing increased activity. The catalytic enhancement has been attributed to the presence of oxygen vacancies in the CTO structure, acting as available active sites for oxygen adsorption, facilitating a faster ORR [37]. In the present work, the most promising composite catalyst formulation (Pt/C:CTO 1:1) has been investigated at the cathode of a DMFC in order to increase the performance. Furthermore, an evaluation of the methanol tolerance characteristics of this composite cathode is herein presented.

2. Results

2.1. Physicochemical Characterization

A commercial 20% Pt/C was employed as a reference catalyst for the ORR. Figure 1 shows the XRD patterns of both the CTO powder, with an orthorhombic phase characterized by Pnma space group, and the Pt/C catalyst, with typical diffraction peaks of the face-centered cubic (fcc) structure of platinum. The average crystallite size of Pt and CTO was 2.1 ± 0.1 nm and 145 ± 5 nm, respectively. It appears that the Pt particles are very small, nanometric in size; furthermore, an amorphous halo is evident at about 30–35° 2θ. This commercial 20% Pt/C catalyst was selected due to the relatively high surface area as a consequence of these very small particles.
The catalyst and the CTO additive were mixed together (in an ultrasonic bath) in a weight ratio of 1:1. SEM images of the mixture are reported in Figure 2. The images show a homogeneous distribution of the two compounds, with a prismatic, quasi-cubic shape of the CTO particles and the porous structure of the Pt/C catalyst (the typical morphology of carbon black can be observed in Figure 2a).
As reported in a previous paper [37], the composite material presents a higher electrochemical active surface area (ECSA) compared to the bare Pt/C (74 vs. 57 m2 g−1), as determined by cyclic voltammetry (CV). This indicates that the mixing procedure does not create agglomeration of particles, but helps with increasing the interface and Pt utilization. This finding has been already reported for other transition metal oxides, added as promoters of Pt for different reactions (methanol or ethanol electro-oxidation, etc.) [38,39,40,41,42]. In this case, it appears that the presence of a sub-stoichiometric CTO increases the ECSA due to a local coordination of CTO particles with Pt [37].

2.2. DMFC Results

The Pt/C:CTO 1:1 composite material was investigated at the cathode of a DMFC, using a low Pt loading (0.5 mg cm−2) at the electrode in order to assess the effect of the CTO addition on the electrochemical behavior. The same experiments were carried out on a membrane-electrode assembly (MEA) equipped with a bare Pt/C catalyst at the cathode, with the same Pt loading, for sake of comparison. The polarization and power density curves recorded for the two MEAs are reported in Figure 3 at three different temperatures (30, 60 and 90 °C), feeding the anode with a 2 M methanol solution.
From the polarization behavior at the different temperatures, it appears that the presence of the CTO additive promotes the oxygen reduction reaction, as already demonstrated by a previous work dealing with ex-situ RDE analysis [37]. In fact, by comparing the behavior at all investigated temperatures, the composite-electrode-based MEA showed a lower loss of potential in all the regions of the polarization curve, but, in particular, in the activation and ohmic regions. At higher current density, the diffusion of oxygen in a thicker cathode (due to the presence of CTO) for the composite electrode likely produced a slight change in the slope of the polarization curve (visible at 30 and 60 °C, not at 90 °C since the polarization curve was interrupted before reaching the mass transfer constraints). The increase in power density, obtained with the CTO-based electrode, was around 15-20% at low temperature (30 and 60 °C), whereas it was more than 40% at higher temperature (90 °C). The maximum power density, close to 120 mW cm−2, reached at 90 °C, is one of the highest values reported in the literature under similar operating conditions (2 M methanol at the anode, oxygen at the cathode under atmospheric pressure, 1.2 and 0.5 mg cm−2 Pt loading at the anode and cathode, respectively) [43]. The enhanced performance obtained with the CTO addition could be due not only to the improved kinetics of ORR, but also to a better methanol tolerance of the composite catalyst. In fact, higher open circuit voltage (OCV) values were recorded in the polarization curves at the different temperatures for the MEA based on CTO additive; this could be related to a lower effect of crossovered methanol on the cathode catalyst produced by the presence of CTO.

2.3. Methanol Tolerance Characteristics of the Composite Electrode: Ex-Situ Experiments

In order to investigate the methanol tolerance properties of the Pt/C:CTO mixture, ORR polarization curves in O2-saturated perchloric acid solution, with and without methanol, were performed in a Rotating Disk Electrode (RDE) configuration (see Section 3, Materials and Methods). For sake of comparison, the same experiments were carried out on the bare Pt/C catalyst. The polarization behavior, without methanol and at an increasing concentration of methanol, is shown in Figure 4.
Regarding the ORR activity without methanol, the Pt/C:CTO 1:1 catalyst showed the most positive onset potential (Eons= 0.960 V), calculated at −0.1 mA cm−2, and the largest limiting current density (jd) value (7 mA cm−2); whereas, the bare Pt/C exhibited an Eons about 10 mV lower than the composite electro-catalyst with a jd value of about 5.8 mA cm−2. As clearly observed, the addition of methanol produces a slight shift of the ORR onset potential towards lower values, a reduction of the limiting current density and the presence of an oxidation peak (due to methanol). In particular, the intensity of the methanol oxidation peak is an indication of the catalytic activity of the catalyst towards that reaction. Since the intensity of the peak for the composite electrode is higher (the current density reached the region of the plot at positive values) than that observed for the bare Pt/C catalyst, it appears that the CTO presence favors the methanol oxidation reaction. This should be translated in a decreasing cathode voltage, due to a mixed potential caused by the simultaneous oxygen reduction and methanol oxidation reactions in the DMFC, larger than that observed for bare Pt/C. However, this was not observed in the fuel cell, since the OCV and the performance were higher for the MEA based on the CTO additive. This could indicate that the promoting effect of the CTO is even larger than expected, since, as also confirmed by the RDE experiments in pure O2, the performance obtained with the composite electrode was exceeding the one with bare Pt/C by 40% at high temperature (90 °C).
From the RDE results reported in Figure 4, it appears that CTO could promote methanol oxidation. To further confirm this feature, methanol oxidation reaction has been investigated in half-cell configuration (catalyst deposited on a glassy carbon working electrode, see Section 3), by comparing the response of CTO-based composite electrode and of Pt/C reference. The results are reported in Figure 5.
An increased current density and a negative shift of the onset potential are clearly observed for the composite Pt/C:CTO catalyst respect to bare Pt/C, confirming a promoting effect of CTO for the methanol oxidation reaction. This phenomenon may be explained through a bifunctional mechanism, in which dehydrogenation occurs on Pt sites and water can adsorb on CTO sites, acting like Ru in PtRu catalysts (benchmark material for methanol electro-oxidation) [2,44,45]. Accordingly, water displacement is favored on CTO sites (also due to the sub-stoichiometry), settling the good activity of some oxides to promote water discharge and adsorption of active oxygen species [2]. There is an analogy between the methanol oxidation and oxygen evolution processes; both require water adsorption and dissociation in oxygen species that, in the present case (methanol oxidation), give rise to surface reaction with adsorbed methanolic residues, producing CO2 [2]. Similar results have been already reported by our group, where noble metal oxides (e.g., IrOx and RuOx) and valve metal oxides (e.g., SnOx and VOx) were added to Pt as promoters for methanol electro-oxidation reaction [46]. Other oxides with a perovskite structure were also found to be good catalysts for oxygen evolution reaction, in particular in alkaline media [47,48]. Thus, it appears that also the perovskite here proposed can have a beneficial influence on the methanol oxidation reaction, reducing the overpotential for water displacement and acting as co-catalyst. Furthermore, the increased ECSA reported for this composite electrode, compared to bare Pt/C, can also play a role in the increased activity. According to this evidence, it appears that the addition of CTO to the current benchmark anode catalyst (PtRu/C) in a DMFC could be of interest in the light of designing a multifunctional catalyst for methanol electro-oxidation. This aspect will be considered in a future work.

3. Materials and Methods

3.1. Synthesis of CaTiO3-δ

The synthesis of non-stoichiometric calcium titanate was carried out using a hydrothermal procedure followed by a calcination treatment, where Pluronic F127 was used as both structure-directing component and reducing agent to allow the formation of oxygen vacancies. This synthesis was carried out according to the details reported in our previous works [37,49].

3.2. Physical-Chemical Characterizations

The phase identification of the synthesized particles was performed using Rigaku D-Max Ultima+ X- ray diffractometer (XRD) (Tokyo, Japan) with a CuKα radiation source at a potential of 40 kV and a current of 20 mA. The crystallites size was calculated using the Maud code.
The morphology analysis of the composite catalyst was conducted by scanning electron microscopy (SEM) using a FEI XL30 SFEG microscope (Hillsboro, Oregon, USA) operating at 25 kV.

3.3. Electrochemical Investigations

3.3.1. Rotating Disk Electrode (RDE) Screening

The electrochemical measurements were carried out using a Metrohm Autolab potentiostat/galvanostat (Utrecht, The Netherlands). Two different catalytic compositions were prepared and compared: Pt/C (E-TEK with 20 wt.% Pt content with respect to C), used as the reference, and Pt/C + CTO, with Pt:CTO 1:1 weight ratio.
A conventional three-electrode cell, formed by a mercury/mercury sulfate (Hg|Hg2SO4, saturated with K2SO4) reference electrode (RE), a high surface Pt wire counter electrode (CE) and a glassy carbon (GC) disk working electrode (WE), was used for the half cell electrochemical characterizations. The two catalytic inks (2 mg mL−1) were prepared by adding the appropriate amount of catalyst powder in isopropyl alcohol and Nafion (30 wt.%), followed by ultrasounds treatment. The working electrode was coated with the prepared catalytic ink. Aliquots of this suspension were dropped onto the glassy carbon in order to obtain a final Pt loading, after the evaporation of the solvent, equal to 50 µg cm−2 for both the above-mentioned compositions. Prior to each deposition, the GC was polished with alumina slurry using an OP-felt polishing cloth.
Different methanol concentrations (0 mM, 1 mM, 4 mM, 12 mM, 20 mM, 50 mM) were studied in an oxygen saturated 0.1 M perchloric acid (HClO4) solution, used as the electrolyte, at room temperature. Linear sweep voltammetry (LSV) was performed from 1.2 V to 0.2 V towards the reversible hydrogen electrode (RHE) with a scan rate of 5 mV s−1 at different rotations speeds (100, 200, 400, 1000, 1600, 2500 rpm). The activity toward methanol oxidation reaction (MOR) was investigated by LSV from 0.1 to 1 V vs. RHE with a scan rate of 5 mV s−1 in a 0.1 M HClO4 in the presence of 2M CH3OH solution.

3.3.2. Direct Methanol Fuel Cell (DMFC) Tests

The two membrane-electrode assemblies (MEAs) were realized by depositing the catalysts via doctor blade technique onto HT-ELAT and LT-ELAT (E-TEK) carbon cloths coated with gas diffusion layers at the anode and cathode, respectively. For the two MEAs, anode catalytic ink was prepared by sonicating 60% PtRu/C (Johnson Matthey, London, UK) and 33 wt.% Nafion ionomer (Ion Power, 5 wt.% solution) in 2-propanol/H2O (3:1 v/v); the obtained slurry was deposited onto the carbonaceous substrate in order to achieve 1.2 ± 0.1 mg·cm−2 Pt loading. The membrane, employed for all the polarization measurements, was Nafion 117. The only experimental variable was related to the cathode catalysts. Pt/C (E-TEK) or Pt/C + CTO (Pt/C:CTO=1:1 weight ratio) was dispersed in 2-propanol/H2O (3:1 v/v) and 33 wt.% Nafion ionomer (Ion Power, 5 wt.% solution) and then deposited onto LT-ELAT with the aim of achieving a low Pt amount (0.5 mg·cm−2). The assembly was realized by hot pressing the membrane between the electrodes at 130 °C and 20 Kgf·cm−2 for 1.5 min.
A 5 cm2 single cell, linked to a Fuel Cell Technologies Inc. test-station (Albuquerque, NM, USA), was employed for DMFC tests. Polarization measurements were recorded by feeding 2 M methanol solution at the anode, with a flow rate of 2 mL·min−1, and fully humidified oxygen at the cathode, with a flow rate of 100 mL·min−1. The performance of each MEA was measured in the temperature range 30–90 °C and atmospheric pressure.

4. Conclusions

A non-stoichiometric calcium titanate CaTiO3-δ (CTO) was synthesized via an original template-driven hydrothermal procedure. The CTO powder was used as additive to Pt/C catalyst in a direct methanol fuel cell (DMFC) cathode. The cell tests revealed a positive effect of the perovskite for the composite electrode (Pt/C:CTO) especially at 90 °C and 2 M methanol, where a 40% increase of power density was obtained compared with the benchmark Pt/C, reaching a maximum power density close to 120 mW cm−2. This was mainly attributed to the presence of oxygen vacancies in the CTO, but also to the increased ECSA caused by the mixing procedure.
The methanol tolerance characteristics of the Pt/C-CTO mixture were investigated in a rotating disk electrode (RDE) configuration, where it was found that the CTO presence favors the methanol oxidation reaction. This indicates that the promoting effect for the ORR of the CTO is even larger than expected, since there is a parasitic reaction of crossovered methanol oxidation that reduces the overall fuel cell performance. Accordingly, this composite catalyst is envisaged as also very promising for applications in the H2-fed polymer electrolyte fuel cell cathode and direct methanol fuel cell anode.

Author Contributions

Conceptualization, M.A.N. and V.B.; methodology, A.S.A.; investigation, L.M. and C.L.V.; data curation, L.M. and C.L.V.; writing—original draft preparation, L.M. and V.B.; writing—review and editing, M.A.N. and V.B.

Funding

This research received no external funding.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Vielstich, W.; Lamm, A.; Gasteiger, H. Handbook of Fuel Cells—Fundamentals, Technology and Applications; Wiley: West Sussex, UK, 2003. [Google Scholar]
  2. Aricò, A.S.; Baglio, V.; Antonucci, V. Direct methanol fuel cells: Hystory, status and perspectives, Chapter 1. In Electrocatalysis of Direct Methanol Fuel Cells: From Fundamentals to Applications; Liu, H., Zhang, J., Eds.; WILEY-VCH Verlag GmbH & Co. KGaA: Weinheim, Germany, 2009; pp. 1–78. [Google Scholar]
  3. Zeng, J.; Francia, C.; Gerbaldi, C.; Baglio, V.; Specchia, S.; Aricò, A.S.; Spinelli, P. Hybrid ordered mesoporous carbons doped with tungsten trioxide as supports for Pt electrocatalysts for methanol oxidation reaction. Electrochim. Acta 2013, 94, 80–91. [Google Scholar] [CrossRef]
  4. Gasteiger, H.A.; Kocha, S.S.; Sompalli, B.; Wagner, F.T. Activity benchmarks and requirements for Pt, Pt-alloy, and non-Pt oxygen reduction catalysts for PEMFCs. Appl. Catal. B 2005, 56, 9–35. [Google Scholar] [CrossRef]
  5. Sgroi, M.F.; Zedde, F.; Barbera, O.; Stassi, A.; Sebastián, D.; Lufrano, F.; Baglio, V.; Aricò, A.S.; Bonde, J.L.; Schuster, M. Cost analysis of direct methanol fuel cell stacks for mass production. Energies 2016, 9, 1008. [Google Scholar] [CrossRef]
  6. Morozan, A.; Jousselme, B.; Palacin, S. Low-platinum and platinum-free catalysts for the oxygen reduction reaction at fuel cell cathodes. Energy Environ. Sci. 2011, 4, 1238–1254. [Google Scholar] [CrossRef]
  7. Nie, Y.; Li, L.; We, Z. Recent advancements in Pt and Pt-free, catalysts for oxygen reduction reaction. Chem. Soc. Rev. 2015, 44, 2168–2201. [Google Scholar] [CrossRef]
  8. Lo Vecchio, C.; Aricò, A.S.; Monforte, G.; Baglio, V. EDTA-derived Co-N-C and Fe-N-C electro-catalysts for the oxygen reduction reaction in acid environment. Renew. Energy 2018, 120, 342–349. [Google Scholar] [CrossRef]
  9. Li, Z.; Gao, Q.; Zhang, H.; Tian, W.; Tan, Y.; Qian, W.; Liu, Z. Low content Pt nanoparticles anchored on N-doped reduced graphene oxide with high and stable electrocatalytic activity for oxygen reduction reaction. Sci. Rep. 2017, 7, 43352. [Google Scholar] [CrossRef]
  10. Lo Vecchio, C.; Sebastiàn, D.; Làzaro, M.J.; Aricò, A.S.; Baglio, V. Methanol-tolerant M–N–C catalysts for oxygen reduction reactions in acidic media and their application in direct methanol fuel cells. Catalysts 2018, 8, 650. [Google Scholar] [CrossRef]
  11. Sebastián, D.; Serov, A.; Artyushkova, K.; Atanassov, P.; Aricò, A.S.; Baglio, V. Performance, methanol tolerance and stability of Fe-aminobenzimidazole derived catalyst for direct methanol fuel cells. J. Power Sources 2016, 319, 235–246. [Google Scholar] [CrossRef]
  12. Saianand, G.; Gopalan, A.-I.; Lee, J.-C.; Sathish, C.I.; Gopalakrishnan, K.; Unni, G.E.; Shanbhag, D.; Dasireddy, V.D.B.C.; Yi, J.; Xi, S.; et al. Mixed copper/Copper-oxide anchored mesoporous fullerene nanohybrids as superior electrocatalysts toward Oxygen Reduction Reaction. Small 2019, 1903937. [Google Scholar] [CrossRef]
  13. Baglio, V.; Di Blasi, A.; D’Urso, C.; Antonucci, V.; Arico, A.S.; Ornelas, R.; Morales-Acosta, D.; Ledesma-Garcia, J.; Godinez, L.A.; Arriaga, L.G.; et al. Development of Pt and Pt-Fe catalysts supported on multiwalled carbon nanotubes for oxygen reduction in direct methanol fuel cells. J. Electrochem. Soc. 2008, 155, B829–B833. [Google Scholar] [CrossRef]
  14. Antolini, E.; Salgado, J.R.C.; Santos, L.G.R.A.; Garcia, G.; Ticianelli, E.A.; Pastor, E.; Gonzalez, E.R. Carbon supported Pt-Cr alloys as oxygen reduction catalysts for direct methanol fuel cells. J. Appl. Electrochem. 2006, 36, 355–362. [Google Scholar] [CrossRef]
  15. Toda, T.; Igarashi, H.; Uchida, M.; Watanabe, M. Enhancement of the electroreduction of oxygen on Pt alloys with Fe, Ni, and Co. J. Electrochem. Soc. 1999, 146, 3750–3756. [Google Scholar] [CrossRef]
  16. Mukerjee, S.; Srinivasan, S.; Soriaga, M.P.; McBreen, J. Role of structural and electronic properties of Pt and Pt alloys on electrocatalysis of oxygen reduction. J. Electrochem. Soc. 1995, 142, 1409–1422. [Google Scholar] [CrossRef]
  17. Shukla, A.K.; Raman, R.K.; Choudhury, N.A.; Priolkar, K.R.; Sarode, P.R.; Emura, S.; Kumashiro, R. Carbon-supported Pt–Fe alloy as a methanol-resistant oxygen-reduction catalyst for direct methanol fuel cells. J. Electroanal. Chem. 2004, 563, 181–190. [Google Scholar] [CrossRef]
  18. Scott, K.; Yuan, W.; Cheng, H. Feasibility of using PtFe alloys as cathodes in direct methanol fuel cells. J. Appl. Electrochem. 2007, 37, 21–26. [Google Scholar] [CrossRef]
  19. Baglio, V.; Aricò, A.S.; Stassi, A.; D’Urso, C.; Di Blasi, A.; Luna, A.M.C.; Antonucci, V. Investigation of Pt-Fe catalysts for oxygen reduction in low temperature direct methanol fuel cells. J. Power Sources 2006, 159, 900–904. [Google Scholar] [CrossRef]
  20. Yang, H.; Coutanceau, C.; Leger, J.-M.; Alonso-Vante, N.; Lamy, C. Methanol tolerant oxygen reduction on carbon-supported Pt–Ni alloy nanoparticles. J. Electroanal. Chem. 2005, 576, 305–313. [Google Scholar] [CrossRef]
  21. Antolini, E.; Salgado, J.R.C.; Gonzalez, E.R. The methanol oxidation reaction on platinum alloys with the first row transition metals: The case of Pt–Co and –Ni alloy electrocatalysts for DMFCs: A short review. Appl. Catal. B 2006, 63, 137–149. [Google Scholar] [CrossRef]
  22. Li, W.; Zhou, W.; Li, H.; Zhou, Z.; Zhou, B.; Sun, G.; Xin, Q. Nano-stuctured Pt–Fe/C as cathode catalyst in direct methanol fuel cell. Electrochim. Acta 2004, 49, 1045–1055. [Google Scholar] [CrossRef]
  23. Gasteiger, H.A.; Markovic, N.M.; Ross, P.N.; Cairns, E.J. Electro-oxidation of small organic molecules on well-characterized Pt-Ru alloys. Electrochim. Acta 1994, 39, 1825–1832. [Google Scholar] [CrossRef]
  24. Chen, Y.; Wang, J.; Meng, X.; Zhong, Y.; Li, R.; Sun, X.; Ye, S.; Knights, S. Pt-SnO2/nitrogen-doped CNT hybrid catalysts for proton-exchange membrane fuel cells (PEMFC): Effects of crystalline and amorphous SnO2 by atomic layer deposition. J. Power Sources 2013, 238, 144–149. [Google Scholar] [CrossRef]
  25. Huang, S.Y.; Ganesan, P.; Popov, B.N. Titania supported platinum catalyst with high electrocatalytic activity and stability for polymer electrolyte membrane fuel cell. Appl. Catal. B 2011, 102, 71–77. [Google Scholar] [CrossRef]
  26. Stassi, A.; Gatto, I.; Baglio, V.; Passalacqua, E.; Aricò, A.S. Oxide supported PtCo alloy catalyst for intermediate temperature polymer electrolyte fuel cells. Appl. Catal. B 2013, 142–143, 15–24. [Google Scholar] [CrossRef]
  27. Mittermeier, T.; Madkikar, P.; Wang, X.; Gasteiger, H.A.; Piana, M. ZrO2 based oxygen reduction catalysts for PEMFCs: Towards a better understanding. J. Electrochem. Soc. 2016, 163, F1543–F1552. [Google Scholar] [CrossRef]
  28. Baglio, V.; Amin, R.S.; El-Khatib, K.M.; Siracusano, S.; D’Urso, C.; Aricò, A.S. IrO2 as a promoter of Pt-Ru for methanol electro-oxidation. Phys. Chem. Chem. Phys. 2014, 16, 10414–10418. [Google Scholar] [CrossRef]
  29. Zuo, G.; Li, B.; Guo, Z.; Wang, L.; Yang, F.; Hou, W.; Zhang, S.; Zong, P.; Liu, S.; Meng, X.; et al. Efficient photocatalytic hydrogen peroxide production over TiO2 passivated by SnO2. Catalysts 2019, 9, 623. [Google Scholar] [CrossRef]
  30. Lee, J.-C.; Gopalan, A.-I.; Sainand, G.; Lee, K.-P.; Kim, W.-J. Preparation of visible light photocatalytic graphene embedded rutile titanium(IV) oxide composite nanowires and enhanced NOx removal. Catalysts 2019, 9, 170. [Google Scholar] [CrossRef]
  31. Abdullah, N.; Kamarudin, S.K. Titanium dioxide in fuel cell technology: An overview. J. Power Sources 2015, 278, 109–118. [Google Scholar] [CrossRef]
  32. Pena, M.A.; Fierro, J.L.G. Chemical structures and performance of perovskite oxides. Chem. Rev. 2001, 101, 1981–2018. [Google Scholar] [CrossRef]
  33. Ge, X.; Sumboja, A.; Wuu, D.; An, T.; Li, B.; Goh, F.W.T.; Hor, T.S.A.; Zong, Y.; Liu, Z. Oxygen reduction in alkaline media: From mechanisms to recent advances of catalysts. ACS Catal. 2015, 5, 4643–4667. [Google Scholar] [CrossRef]
  34. Risch, M. Perovskite electrocatalysts for the oxygen reduction reaction in alkaline media. Catalysts 2017, 7, 154. [Google Scholar] [CrossRef] [Green Version]
  35. Suntivich, J.; Gasteiger, H.A.; Yabuuchi, N.; Nakanishi, H.; Goodenough, J.B.; Shao-Horn, Y. Design principles for oxygen-reduction activity on perovskite oxide catalysts for fuel cells and metal-air batteries. Nat. Chem. 2011, 3, 546–550. [Google Scholar] [CrossRef] [PubMed]
  36. Fabbri, E.; Mohamed, R.; Levecque, P.; Conrad, O.; Kötza, R.; Schmidt, T.J. Unraveling the oxygen reduction reaction mechanism and activity of d-band perovskite electrocatalysts for low temperature alkaline fuel cells. ECS Trans. 2014, 64, 1081–1093. [Google Scholar] [CrossRef]
  37. Mazzapioda, L.; Lo Vecchio, C.; Paolone, A.; Aricò, A.S.; Baglio, V.; Navarra, M.A. Enhancing oxygen reduction reaction catalytic activity using a sub-stoichiometric CaTiO3-δ additive. ChemElectroChem 2019, in press. [Google Scholar] [CrossRef]
  38. Yu, L.; Xi, J. TiO2 nanoparticles promoted Pt/C catalyst for ethanol electro-oxidation. Electrochim. Acta 2012, 67, 166–171. [Google Scholar] [CrossRef]
  39. Wang, Z.; Chen, G.; Xia, D.; Zhang, L. Studies on the electrocatalytic properties of PtRu/C-TiO2 toward the oxidation of methanol. J. Alloys Compd. 2008, 450, 148–151. [Google Scholar] [CrossRef]
  40. Tian, J.; Sun, G.; Jiang, L.; Yan, S.; Mao, Q.; Xin, Q. Highly stable PtRuTiOx/C anode electrocatalyst for direct methanol fuel cells. Electrochem. Commun. 2007, 9, 563–568. [Google Scholar] [CrossRef]
  41. Baglio, V.; Zignani, S.C.; Siracusano, S.; Stassi, A.; D’Urso, C.; Aricò, A.S. Composite anode electrocatalyst for direct methanol fuel cells. Electrocatalysis 2013, 4, 235–240. [Google Scholar] [CrossRef]
  42. Sebastiàn, D.; Stassi, A.; Siracusano, S.; Lo Vecchio, C.; Aricò, A.S.; Baglio, V. Influence of metal oxide additives on the activity and stability of PtRu/C for methanol electro-oxidation. J. Electrochem. Soc. 2015, 162, F713–F717. [Google Scholar] [CrossRef]
  43. Thiagarajan, V.; Karthikeyan, P.; Thanarajan, K.; Neelakrishnan, S.; Manoharan, R.; Chen, R.; Fly, A.; Anand, R.; Karuppa Raj, T.R.; Kumar, N.S. Experimental investigation on DMFCs using reduced noble metal loading with NiTiO3 as supportive material to enhance cell performances. Int. J. Hydrogen Energy 2019, 44, 13415–13423. [Google Scholar] [CrossRef]
  44. Arico, A.S.; Baglio, V.; Di Blasi, A.; Modica, E.; Antonucci, P.L.; Antonucci, V. Analysis of the high-temperature methanol oxidation behaviour at carbon-supported Pt/Ru catalysts. J. Electroanal. Chem. 2003, 557, 167–176. [Google Scholar] [CrossRef]
  45. Tsiouvaras, N.; Martınez-Huerta, M.V.; Paschos, O.; Stimming, U.; Fierro, J.L.G.; Pena, M.A. PtRuMo/C catalysts for direct methanol fuel cells: Effect of the pretreatment on the structural characteristics and methanol electrooxidation. Int. J. Hydrogen Energy 2010, 35, 11478–11488. [Google Scholar] [CrossRef]
  46. Amin, R.S.; El-Khatib, K.M.; Siracusano, S.; Baglio, V.; Stassi, A.; Arico, A.S. Metal oxide promoters for methanol electro-oxidation. Int. J. Hydrogen Energy 2014, 39, 9782–9790. [Google Scholar] [CrossRef]
  47. Alegre, C.; Modica, E.; Rodlert-Bacilieri, M.; Mornaghini, F.C.; Aricò, A.S.; Baglio, V. Enhanced durability of a cost-effective perovskite-carbon catalyst for the oxygen evolution and reduction reactions in alkaline environment. Int. J. Hydrogen Energy 2017, 42, 28063–28069. [Google Scholar] [CrossRef]
  48. Alegre, C.; Modica, E.; Aricò, A.S.; Baglio, V. Bifunctional oxygen electrode based on a perovskite/carbon composite for electrochemical devices. J. Electroanal. Chem. 2018, 808, 412–419. [Google Scholar] [CrossRef]
  49. Mazzapioda, L.; Navarra, M.A.; Trequattrini, F.; Paolone, A.; Elamin, K.; Martinelli, A.; Palumbo, O. Composite Nafion membranes with CaTiO3-δ additive for possible applications in electrochemical devices. Membranes 2019, 9, 143. [Google Scholar] [CrossRef] [Green Version]
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Figure 1. X-ray diffraction patterns of the synthesized CaTiO3-δ powder and commercial 20% Pt/C catalyst.
Figure 1. X-ray diffraction patterns of the synthesized CaTiO3-δ powder and commercial 20% Pt/C catalyst.
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Figure 2. Scanning Electron Microscopy (SEM) images of the Pt/C-CTO (1:1) mixture at (a) high and (b) low magnification.
Figure 2. Scanning Electron Microscopy (SEM) images of the Pt/C-CTO (1:1) mixture at (a) high and (b) low magnification.
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Figure 3. Comparison of DMFC polarization and power density curves for the MEAs equipped with the bare Pt/C (black) and the composite Pt/C:CTO (red) cathode catalysts at different temperatures (30, 60 and 90 °C).
Figure 3. Comparison of DMFC polarization and power density curves for the MEAs equipped with the bare Pt/C (black) and the composite Pt/C:CTO (red) cathode catalysts at different temperatures (30, 60 and 90 °C).
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Figure 4. ORR linear sweep voltammetry (in RDE at 1600 rpm) without methanol and at increased concentrations of methanol for the 20% Pt/C (left) and the Pt/C:CTO 1:1 mixture (right).
Figure 4. ORR linear sweep voltammetry (in RDE at 1600 rpm) without methanol and at increased concentrations of methanol for the 20% Pt/C (left) and the Pt/C:CTO 1:1 mixture (right).
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Figure 5. Linear sweep voltammetry for the methanol oxidation reaction in 0.1 M HClO4 solution and 2 M methanol on Pt/C (black) and Pt/C:CTO (1:1) (red) mixture.
Figure 5. Linear sweep voltammetry for the methanol oxidation reaction in 0.1 M HClO4 solution and 2 M methanol on Pt/C (black) and Pt/C:CTO (1:1) (red) mixture.
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MDPI and ACS Style

Mazzapioda, L.; Lo Vecchio, C.; Aricò, A.S.; Navarra, M.A.; Baglio, V. Performance Improvement in Direct Methanol Fuel Cells by Using CaTiO3-δ Additive at the Cathode. Catalysts 2019, 9, 1017. https://doi.org/10.3390/catal9121017

AMA Style

Mazzapioda L, Lo Vecchio C, Aricò AS, Navarra MA, Baglio V. Performance Improvement in Direct Methanol Fuel Cells by Using CaTiO3-δ Additive at the Cathode. Catalysts. 2019; 9(12):1017. https://doi.org/10.3390/catal9121017

Chicago/Turabian Style

Mazzapioda, Lucia, Carmelo Lo Vecchio, Antonino Salvatore Aricò, Maria Assunta Navarra, and Vincenzo Baglio. 2019. "Performance Improvement in Direct Methanol Fuel Cells by Using CaTiO3-δ Additive at the Cathode" Catalysts 9, no. 12: 1017. https://doi.org/10.3390/catal9121017

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