Effects of Pt/C, Pd/C and PdPt/C anode catalysts on the performance and stability of air breathing direct formic acid fuel cells

doi:10.1016/j.ijhydene.2011.04.081

International Journal of Hydrogen Energy

Volume 36, Issue 14, July 2011, Pages 8518-8524

https://doi.org/10.1016/j.ijhydene.2011.04.081 Get rights and content

Abstract

Pt/C, Pd/C and PdPt/C catalysts are potential anodic candidates for electro-oxidation of formic acid. In this work we designed a miniature air breathing direct formic acid fuel cell, in which gold plated printed circuit boards are used as end plates and current collectors, and evaluated the effects of anode catalysts on open circuit voltage, power density and long-term discharging stability of the cell. It was found that the cell performance was strongly anode catalyst dependent. Pd/C demonstrated good catalytic activity but poor stability. A maximum power density of 25.1 mW cm⁻² was achieved when 5.0 M HCOOH was fed as electrolyte. Pt/C and PdPt/C showed poor activity but good stability, and the cell can discharge for about 10 h at 0.45 V (Pt/C anode) and 15 h at 0.3 V (PdPt/C) at 20 mA.

Highlights

► A miniature air breathing DFAFC with focus on the effects of anode catalysts was designed and evaluated. ► The cell performance, stability, Faradic/energy efficiency was strongly anode catalyst dependent. ► Pd/C have good catalytic activity but with poor stability. ► Pt/C and PdPt/C as anode catalyst have poor activity but with good stability.

Introduction

The inherent advantages of higher open circuit potential [1], safer fuel (non-flammable and non-toxic) [2], [3], lower fuel crossover through Nafion membrane [4], [5] and faster room temperature kinetics for direct formic acid fuel cell (DFAFC) relative to direct methanol fuel cell (DMFC) made the former ideal candidate for portable device applications [6]. The low formic acid crossover allows for use of thin membrane as well as high fuel concentration (as high as 20 M [1], [7]), consequently boosted energy density of the DFAFC. Compared with DFAFC operated in active mode, passive air breathing formic acid fuel cell, in particular, is receiving increasing attention [8], [9], [10] due to the advantages of operation without additional devices (such as pumps for feeding fuel and air fans for cooling system used in active fuel cells [11]). Undoubtedly, the simpler configuration of the passive DFAFC (relative to active one) can meet the stringent requirements of portable applications such as portability and low cost.

In our previous works [12], [13], we have successfully demonstrated the possibility of fabrication single and twin DFAFC using printed circuit board (PCB) as end plate and current collector. A line of parameters have been optimized and the cell showed satisfactory performance. In our preliminary study we have found that the use of different anode catalysts significantly affected the cell power density and stability.

Pt-based [14], [15], [16] or Pd-based [17], [18], [19], [20] catalysts are commonly used for electro-oxidation of formic acid. It has been reported that Pd-based catalysts are more effective than those of Pt-based catalysts due to its insensitivity to the dehydration of formic acid (thus less CO poisoning) [21]. For example, carbon supported Pd and Pd-based catalysts have been proven to be more active to the formic acid oxidation relative to Pt-based catalysts in the literatures [17], [18]. Moreover, previous studies have demonstrated that anode catalyst composition affects active cell performance too [15], [21]. Unfortunately, these investigations are mostly conducted in half cell and the dynamic behavior of catalysts evaluated by linear sweep or cyclic voltammetry can hardly reflect the cell stability and performance. Pan et al. [22] in a recent study investigated a DFAFC with Pd anode catalysts and their studies showed that Pd catalysts suffered poor stability and the performance decay under constant current was significant. It is therefore perceived that investigation of cell performance and stability focusing on the intensively studied catalysts (Pt/C, Pd/C and PdPt/C) would be of significance.

In this work, we designed a miniature air breathing DFAFC based on PCB technology and compared the cell performance when three different anode catalysts were used (home-made Pd/C, Pt/C and PdPt/C). The effects of different anode catalysts on the cell performance, stability and Faradic/energy efficiency are investigated.

Section snippets

Experimental

The miniature air breathing DFAFC was designed based on PCB technology. Gold coated PCBs were used as current collectors and end plate. Current collectors, membrane electrode assembly (MEA), diffusion layers, gaskets and fuel reservoir were assembled together to fabricate the cell as shown in Fig. 1. Details on the cell configuration can be found in the reference [12].

MEA was fabricated using a ‘direct catalyst spraying’ technique [23]. A certain amount of catalyst powders was dispersed into

Catalyst morphology

Fig. 2 shows the XRD patterns of Pd/C, Pt/C and PdPt/C. The diffraction peak centered at around 25° in each catalyst is the characteristic of XC-72R carbon support, indicating a weak graphitic nature of the support. The other three peaks correspond to the planes (111), (200) and (220), featuring the face-centered cubic (f.c.c) crystalline structure [17]. Since Pt and Pd have very close lattice constants (lattice mismatch is 2.4%), it is impossible to make a distinction between Pt and Pd [24].

Conclusions

A miniature air breathing DFAFC based on the PCB technology was designed and evaluated. The cell performance was evaluated with particular emphasis on the use of different home-made anode catalyst including Pd/C, Pt/C and PdPt/C. It was found that the cell with Pd/C anode showed good catalytic activity but poor stability, and it delivered the highest output voltage during long-term discharging. The cell with Pt/C anode shows a high stable voltage and the cell with anodic PdPt/C can maintain

Acknowledgments

We would like to thank National Natural Science Foundation of China (Project Nos. 20673040, 20876062, 21076089), the Ministry of Science and Technology of China (Project No. 2009AA05Z119), and Department of Science and Technology of Guangdong Province (Project No. 2004A11004003) for financial support of this work.

References (28)

C. Rice et al.
Direct formic acid fuel cells
J Power Sources
(2002)
S. Ha et al.
A miniature air breathing direct formic acid fuel cell
J Power Sources
(2004)
K.J. Jeong et al.
Fuel crossover in direct formic acid fuel cells
J Power Sources
(2007)
Y.-W. Rhee et al.
Crossover of formic acid through Nafion^® membranes
J Power Sources
(2003)
U.B. Demirci
Direct liquid-feed fuel cells: thermodynamic and environmental concerns
J Power Sources
(2007)
W.S. Jung et al.
Analysis of palladium-based anode electrode using electrochemical impedance spectra in direct formic acid fuel cells
J Power Sources
(2007)
Y.Y. Kang et al.
Effect of Nafion aggregation in the anode catalytic layer on the performance of a direct formic acid fuel cell
J Power Sources
(2010)
J. Yeom et al.
Passive direct formic acid microfabricated fuel cells
J Power Sources
(2006)
S. Ha et al.
Characterization of a high performing passive direct formic acid fuel cell
J Power Sources
(2006)
P. Hong et al.
Design, fabrication and performance evaluation of a miniature air breathing direct formic acid fuel cell based on printed circuit board technology
J Power Sources
(2010)

P. Hong et al.

A miniature passive direct formic acid fuel cell based twin-cell stack with highly stable and reproducible long-term discharge performance

J Power Sources

(2011)

B. Habibi et al.

Electrocatalytic oxidation of formic acid and formaldehyde on platinum nanoparticles decorated carbon-ceramic substrate

Int J Hydrogen Energy

(2010)

C. Rice et al.

Catalysts for direct formic acid fuel cells

J Power Sources

(2003)

P. Waszczuk et al.

A nanoparticle catalyst with superior activity for electrooxidation of formic acid

Electrochem Commun

(2002)

Cited by (74)

Electrocatalytic activities of platinum and palladium catalysts for enhancement of direct formic acid fuel cells: An updated progress
2023, Alexandria Engineering Journal
Direct formic acid fuel cells (DFAFCs) have become an important technology and a clean energy source for various applications. However, some drawbacks in DFAFC applications, such as sluggish kinetics of formic acid oxidation (FAO) reaction at the anodic side, significantly affect DFAFC performance. An excellent catalyst, platinum (Pt), is very effective and performs excellently in FAO, but it is expensive and tends to form carbon monoxide-poisoning species on the catalyst surface. Therefore, new strategies must be developed to overcome problems related to Pt and simultaneously reduce or replace the use of Pt catalysts. This review paper covers the electrocatalytic activities of platinum and palladium (Pd)-based catalysts, which are commercial catalysts and effective for FAO and DFAFC applications. In this paper, the current progress of electrocatalyst development for anodic FAO and DFAFC applications using commercial Pt and Pd catalysts is presented, focusing on the understanding of Pt and Pd catalytic activities with the addition of alloys, metallic metals, trimetallic/tetrametallic metals, transition metals, and metal oxides. Highly potential nanostructured carbon catalyst supports (graphene-based materials, carbon nanotubes, carbon nanofibers, and graphitic carbon nitride) for FAO and DFAFC applications are also discussed. This review article also examines the literature related to Pt and Pd electrocatalysts on the synthesis routes, electrochemical conditions, and fuel cell performance within 10 years from 2013 until 2023. The challenges and strategies for electrocatalyst commercialization in the field are discussed at the end of the paper.
Amendment of palladium nanocubes with iron oxide nanowires for boosted formic acid electro−oxidation
2023, Arabian Journal of Chemistry
To quickly move the formic acid (FA) fuel cells closer to a real commercialization, an inexpensive, efficient, and durable electrocatalyst for ~~the~~ direct FA electro-oxidation (FAEO) was developed. This involved a sequential modification of a glassy carbon (GC) substrate with palladium nanocubes (ca. 70 nm, nano-Pd) and iron oxide nanowires (nano-FeO_x, ca. 40 nm and 150 nm in average diameter and length, respectively). The deposition sequence and loading level of nano-FeO_x in the catalyst were optimized to minimize the catalyst's poisoning with CO that might probably release from a parallel dehydration of FA or from CO₂ reduction. Surprisingly, the FeO_x/Pd/GC catalyst exhibited a high (21.6 mA cm⁻²) specific activity for FAEO, which denoted ca. 7 times that of the “pristine” Pd/GC catalyst. This was synchronized with a better (up to fivefold increase in turnover frequency) “long-termed” stability that extended for 90 min of continuous electrolysis at room temperature. A successful effort was dedicated to improving ~~more~~ the catalyst's stability by activating the catalyst electrochemically at –0.5 V vs Ag/AgCl/KCl (sat.) in 0.2 mol L⁻¹ NaOH. The CO stripping agreed perfectly with the impedance analysis in appending the observed enhancement in the catalytic efficiency of FAEO to a favorable electronic modulation at the Pd surface that boosted the oxidative desorption of poisoning CO species at a lower potential.
Experimental investigation of the stability and emission characteristics of premixed formic acid-methane-air flames in a swirl combustor
2023, International Journal of Hydrogen Energy
Formic acid (FA) is a potential hydrogen energy carrier and low-carbon fuel by reversing the decomposition products, CO₂ and H_2, back to restore FA without additional carbon release. However, FA-air mixtures feature high ignition energy and low flame speed; hence stabilizing FA-air flames in combustion devices is challenging. This study experimentally investigates the flame stability and emission of swirl flames fueled with pre-vaporized formic acid-methane blends over a wide range of formic acid fuel fractions. Results show that by using a swirl combustor, the premixed formic acid-methane-air flames could be stabilized over a wide range of FA fuel fractions, Reynolds numbers, and swirl numbers. The addition of formic acid increases the equivalence ratios at which the flashback and lean blowout occur. When Reynolds number increases, the equivalence ratio at the flashback limit increases, but that decreases at the lean blowout limit. Increasing the swirl number has a non-monotonic effect on stability limits variation because increasing the swirl number changes the axial velocity on the centerline of the burner throat non-monotonically. In addition, emission characteristics were investigated using a gas analyzer. The CO and NO concentrations were below 20 ppm for all tested conditions, which is comparable to that seen with traditional hydrocarbon fuels, which is in favor of future practical applications with formic acid.
Augmented formic acid electro-oxidation at a co-electrodeposited Pd/Au nanoparticle catalyst
2022, Journal of Saudi Chemical Society
In this study, the formic acid electro-oxidation reaction (FAEOR) was catalyzed on a Pd-Au co-electrodeposited binary catalyst. The kinetics of FAEOR were intensively impacted by changing the Pd²⁺:Au³⁺ molar ratio in the deposition medium. The Pd₁-Au₁ catalyst (for which the Pd²⁺:Au³⁺ molar ratio was 1:1) acquired the highest activity with a peak current density for the direct FAEOR (I_p) of 4.14 mA cm⁻² (ca. 13- times higher than that (ca. 0.33 mA cm⁻²) of the pristine Pd₁-Au₀ catalyst). It also retained the highest stability that was denoted in fulfilling ca. 0.292 mA cm⁻² (ca. 19-times higher than 0.015 mA cm⁻² of the pristine Pd₁-Au₀ catalyst) after 3600 s of continuous electrolysis at 0.05 V. The CO stripping and impedance measurements confirmed, respectively, the geometrical and electronic enhancements in the proposed catalyst.
Enhanced electrochemical glucose oxidation in alkaline solution over indium decorated carbon supported palladium nanoparticles
2020, Materials Chemistry and Physics
Citation Excerpt :
CO binds to the active sites of catalyst with strongly bonds, lowering the activity of the catalyst. The cost of Pt-based catalysts is also high [43,44]. Conversely, Pd-based catalysts are both cost-effective and stable against CO poisoning [13].
At present, carbon nanotube (CNT) supported In modified Pd catalysts are prepared at varying Pd:In ratios via NaBH₄ reduction method to investigate the synergetic effect of Pd and In monometallic catalysts through glucose electrooxidation. These catalysts are characterized by advanced surface analytical techniques, namely, inductively coupled plasma-mass spectrometry (ICP-MS) with Agilent 7800 ICP-MS, N₂ adsorption-desorption measurements (BET) with Micromeritics 3Flex equipment Tristar II 3020 equipped, PANalytical Empyrean device-ray diffractometer (XRD), Hitachi HighTech HT7700 high resolution-transmission electron microscope (HR-TEM), and scanning electron microscope (SEM). Electrochemical measurements are performed by using cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) by CHI660E potentiostat in a three electrode system. The characterization results show that all catalysts are successfully synthesized at desired molar composition. For PdIn (90:10)/CNT catalyst, the crystal size obtained from HR-TEM is 2.36 nm and BET surface area is 212.28 cm²g^-1.5% PdIn(90:10)/CNT catalyst exhibits the best catalytic activity, lowest charge transfer resistance (Rct), and a long term stability compared to Pd, In, other Pd:In bimetallic catalysts. EIS and CA results are in a good agreement with CV results.
High performance formic acid fuel cell benefits from Pd–PdO catalyst supported by ordered mesoporous carbon
2020, International Journal of Hydrogen Energy
Formic acid as a renewable fuel can be converted to clean electricity in fuel cells by high-efficient electrochemical oxidation. The conversion rate is fundamentally dictated by the synergy of interactive aspects: catalytic activity, accessibility to active sites, electron transfer, and anti-poisoning stability. For the first time, ordered mesoporous carbon (OMC) is used as the substrate for Pd–PdO catalyst for fuel cells. The unique ordered pore-channel network of OMC can enhance the spatial dispersion of Pd nanoparticles on the pore-channel wall, while the hollow pore-channel can facilitate reactant transport. Microwave and annealing treatments are found to enhance the chemical reduction and to strengthen the anchoring of Pd–PdO catalyst on OMC substrate, respectively. The OMC supported Pd–PdO catalyst (Pd–PdO/OMC) shows 1.7-fold and an order of magnitude higher mass activity and stability as compared to commercial Pd/C catalyst. For fuel cell testing, the Pd–PdO/OMC catalyst is applied to an air-breathing microfluidic fuel cell and achieves a maximum power density of 63.0 mW cm⁻², at least one-fold higher than similar previous reports.

View all citing articles on Scopus

View full text