Formic Acid Fuel Cells Research Articles

Optimization of Pd–Co–M (M= Cu, Au, Ni) Catalysts for the Oxidation of Formic Acid Using Scanning Electrochemical Microscopy

Formic acid, a versatile substance with applications as both a fuel and hydrogen storage material, emerges as a promising energy source. When utilized as a hydrogen storage material, a single liter of formic acid yields an impressive 590 liters of hydrogen gas under ambient conditions. Furthermore, as a fuel, the Direct Formic Acid Fuel Cell (DFAFC) stands out as a potential energy solution due to its elevated open-circuit voltage, low toxicity, and reduced permeability of high molecular weight membranes. Efficient catalysts play a pivotal role in enhancing the formic acid oxidation reaction, thereby diminishing the anode overpotential and amplifying the hydrogen production efficiency of DFAFC. The conventional method of manually testing each catalyst for optimal formic acid oxidation performance is both time-consuming and resource-intensive. Consequently, this study employs a substrate collection method based on a scanning electrochemical microscope (SECM) microelectrode for catalyst screening. A ternary catalyst array, primarily comprising PdCo with supplementary elements (Au, Cu, Ni), was crafted using the innovative concept of compositional assembly. The SECM facilitated the determination of the catalyst's surface morphology, energy-dispersive spectroscopy gauged the catalyst composition, and X-ray diffraction, along with X-ray photoelectron spectroscopy, confirmed the crystalline structure composition. To delve into the kinetic aspects of the catalyst for formic acid oxidation, a comprehensive analysis was carried out using cyclic voltammetry, stripping voltammetry, electrochemical impedance spectroscopy, and Tafel slope analysis. The outcomes unveiled that the optimal proportions for the ternary catalysts were Pd2Co6Au2, Pd2Co6Cu2, and Pd2Co6Ni2, with Pd2Co6Au2 exhibiting superior attributes such as lower overpotential, heightened resistance to CO poisoning, and enhanced catalytic activity for formic acid oxidation.

Construction of H-Doped PdB Nanocrystals as Electrocatalysts to Modulate Formic Acid Oxidation.

The strong ligand effect in B-doped Pd-based (PdB) catalysts renders them a promising anode for constructing formic acid fuel cells (FAFCs) exhibiting high power density and outstanding stability. However, the enhancement of the oxidation barrier is unavoidable in this alloy system owing to the electron transfer (ET) from B to Pd. In this study, a hydrogen doping strategy is employed to open charge freedom in PdB compounds and boost their formic acid oxidation reaction (FAOR) activity by suppressing the ET process. The resulting hydrogen-doped PdB (PdBH) exhibits an ultrahigh mass activity of up to 1.2A mg-1 Pd, which is 3.23 times that of the PdB catalyst and 9.55 times that of Pd black. Detailed experimental and theoretical studies show that the interstitial hydrogen leads to enhanced orbital hybridization and reduced electron density around Pd. This optimized ligand effect weakens the carbon monoxide adsorption and increases the direct pathway preference of PdBH, resulting in its outstanding catalytic activity for the FAOR. The development of this high-performance hydrogen-doped PdB catalyst is an important step toward the construction of advanced light element co-doped metal catalysts.

(Digital Presentation) Power-Generation and Mass-Transport Characteristics of Direct Formic Acid Fuel Cell Using Pore-Designed Anode Electrode

Controlling of mass transport in the anode catalyst layer has become one of the major challenges in Direct Formic Acid Fuel Cells (DFAFCs) owing to the poor formic acid transport and crossover. This study is aim to introduce the microfiber-pores designed anode catalyst layers by mean to improve the mass transport limitation and eventually improving the performance of DFAFCs. Polystyrene fibers (PSFs) were fabricated with different diameter by electrospinning prior to control their length by ultrasonic homogenization. Different amount of PSF as a pore forming agent were then added to the catalyst ink before catalyst coated membrane (CCM) were made by spraying the catalyst ink on the membrane. The CCM were then soaked in ethyl acetate solution to remove the PSF in order to improve the porous structure of anode catalyst layer. Different diameter and amount of PSFs exhibited different pore properties of the catalyst layer and its effect on the mass transport and the performance of DFAFC were then investigated. From the results, the microfiber-pores designed anode catalyst layers showed better performance remarkably at the higher current density region as compared to the conventional anode catalyst layer. Moreover, it was also found that there were optimum diameter and amount of PSF used for the highest performance of DFAFC. This could be attributed to the existence of the microfiber-pores have provide larger active catalyst region which accelerate the fuel transport and the CO2 emission in anode catalyst layer. Thus, these results indicate that the introduction of the microfiber-pores on the anode catalyst layer is a promising approach in order to improve the mass transport resistance, leading to enhance the DFAFCs performance.

Recent Advances in Anode Electrocatalysts for Direct Formic Acid Fuel Cells - Part I - Fundamentals and Pd Based Catalysts.

Direct formic acid fuel cells (DFAFCs) have gained immense importance as a source of clean energy for portable electronic devices. It outperforms other fuel cells in several key operational and safety parameters. However, slow kinetics of the formic acid oxidation at the anode remains the main obstacle in achieving a high power output in DFAFCs. Noble metal-based electrocatalysts are effective, but are expensive and prone to CO poisoning. Recently, a substantial volume of research work have been dedicated to develop inexpensive, high activity and long lasting electrocatalysts. Herein, recent advances in the development of anode electrocatalysts for DFAFCs are presented focusing on understanding the relationship between activity and structure. This review covers the literature related to the electrocatalysts based on noble metals, non-noble metals, metal-oxides, synthesis route, support material, and fuel cell performance. The future prospects and bottlenecks in the field are also discussed at the end.

Catalyst Composites of Palladium and N-Doped Carbon Quantum Dots-Decorated Silica and Reduced Graphene Oxide for Enhancement of Direct Formic Acid Fuel Cells.

Pd-based catalysts consisting of Pd nanoparticles on nitrogen-doped carbon quantum dots (N-CQDs) modified silica (SiO2) and reduced graphene oxide have been synthesized through reduction for use as catalysts for improved formic acid oxidation. The structure, morphology, chemical composition, functional groups, and porosity of the synthesized catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, and Brunauer–Emmett–Teller (BET) spectroscopy, respectively. Their electrocatalytic activities were also evaluated by electrochemical measurements. The differences in the average particle sizes found for Pd/N-CQDs-SiO2-rGO, Pd/N-CQDs-rGO, and Pd/rGO were 4.81, 5.56, and 6.31 nm, respectively. It was also found that the Pd/xN-CQDs-SiO2-yrGO composite catalysts (where x and y is 1 to 4) can significantly improve the activity and stability toward formic acid electrooxidation compared with Pd/rGO and commercial Pt/C. The mass activities of Pd/N-CQDs-SiO2-rGO, Pd/N-CQDs-rGO, and Pd/rGO were 951.4, 607.8, and 157.6 mA g–1, respectively, which was ca. 6–7 times compared with Pd/rGO and approximately 3–4 times compared with commercial Pt/C. With low potential for CO oxidation and high current intensity, the composites of rGO, SiO2, and N-CQDs into Pd-based catalysts improved the catalytic activity of the prepared catalyst for the oxidation of formic acid in acidic media. The value of the Tafel slope designated that the chief path of the prepared catalysts is the dehydrogenation process. These prepared catalysts exhibit promise toward the development of high-performance Pd-based electrocatalysts for formic acid oxidation.

Novel Superaerophobic Anode with Fern‐Shaped Pd Nanoarray for High‐Performance Direct Formic Acid Fuel Cell

AbstractDirect formic acid fuel cells (DFAFCs) possess the advantages of high power density and theoretical cell potential. Exploring robust catalysts for electrochemical formic acid electro‐oxidation (FAO) is greatly essential for the wide spread uptake of DFAFCs. However, many electrodes with attractive catalysts suffer limited mass transport due to sluggish CO2 bubble growth and departure steps on its surface. In this study, a superaerophobic electrode is developed by depositing fern‐shaped palladium nanostructured arrays on the carbon paper (Pd‐nanoarray@CP). Its unique superaerophobic feature successfully facilitates the CO2 bubble releasing from the catalyst surface in a significantly small size. With the merits of specific nanoarray morphology, superior under water superaerophobicity, and rapid gas bubble release, the Pd‐nanoarray@CP shows fast charge/mass transport rate, high electrocatalytic activity, and great stability for FAO. A direct formic acid fuel cell equipped with the Pd‐nanoarray@CP anode is successfully fabricated on a microfluidic platform. A peak power density of 35.8 mW cm−2 and limiting current density of 173.3 mA cm−2 are obtained, respectively, which are 49.2% and 33.0% higher than that of conventional Pd‐black anodes. The electrode with superaerophobic interface allows deeper insight into the mechanism of FAO efficiency and holds promise for possible applications of commercially viable DFAFCs.

Formic Acid to Power towards Low‐Carbon Economy

AbstractThe storage and utilization of low‐carbon electricity and decarbonization of transportation are essential components for the future energy transition into a low‐carbon economy. While hydrogen has been identified as a potential energy carrier, the lack of viable technologies for safe and efficient storage and transportation of H2 greatly limits its applications and deployment at scale. Formic acid (FA) is considered one of the promising H2 energy carriers because of its high volumetric H2 storage capacity of 53 g H2/L, and relatively low toxicity and flammability for convenient and low‐cost storage and transportation. FA can be employed to generate electricity either in direct FA fuel cells (FCs) or indirectly as an H2 source for hydrogen FCs. FA can enable large‐scale chemical H2 storage to eliminate energy‐intensive and expensive processes for H2 liquefaction and compression and thus to achieve higher efficiency and broader utilization. This perspective summarizes recent advances in catalyst development for selective dehydrogenation of FA and high‐pressure H2 production. The advantages and limitations of FA‐to‐power options are highlighted. Existing life cycle assessment (LCA) and economic analysis studies are reviewed to discuss the feasibility and future potential of FA as a fuel.

Porous Electrodes from Self-Assembled 3d Jointed Pd Polyhedra for Direct Formic Acid Fuel Cells

Porous Electrodes from Self-Assembled 3d Jointed Pd Polyhedra for Direct Formic Acid Fuel Cells

Synthesis of Palladium–Tungsten Metallene-Constructed Sandwich-Like Nanosheets as Bifunctional Catalysts for Direct Formic Acid Fuel Cells

Synthesis of Palladium–Tungsten Metallene-Constructed Sandwich-Like Nanosheets as Bifunctional Catalysts for Direct Formic Acid Fuel Cells

Direct Formic Acid Fuel Cell Anode Catalyst Layer: Enhanced Mass Transport with Increased Porosity

Batteries are the predominant portable power source, but are inefficient due to their limited charge capacity, lengthy recharging times, and exponential degradation. Direct formic acid fuel cells present a sustainable replacement to batteries with their instantaneous refueling times and high efficiency. However, small pore size (~20 nm) between the agglomerates in the anode catalyst layer and two-phase flow hinders the mass transport and reduces the cell performance. Therefore, enhancing the cell performance also requires the two-phase flow optimization of the liquid reactant (formic acid, HCOOH) and gaseous product (carbon dioxide, CO2). To accomplish this, pore-forming agent (magnesium oxide, MgO) was incorporated during the anode catalyst layer fabrication and subsequent removal leaving behind lager pores to improve the two-phase flow through the anode catalyst layer.In 2012, the addition and subsequent removal of pore-former (lithium carbonate, LiCO3), formed ~10 μm pores within the anode catalyst layer.[1] The optimal performance was found for pores formed from with 17.5 wt% LiCO3; however, the formic acid electrooxidation charge transfer activity was reduced, due to the size of the pore-former increased the separation of the agglomerates and reduced the connected electrochemical surface area.To avoid damaging the integrity of the anode catalyst layer, previous work to integrate a smaller pore-former MgO (~50 nm), into the anode catalyst layer was investigated. [2] Compared to an anode catalyst layer without pore-former, 25 wt% pore-former increased the electrochemical surface area and cell performance by 293% and 86%, respectfully. The present study aims to further explore varying wt% of pore-former with additional sonication of the catalyst/ionomer ink prior to fabrication. The uniformity and effect of agglomerate size vs. MgO addition will be explored by quantifying the viscosity of the catalyst ink. [3] Bauskar, A.S. and Rice, C.A., Impact of Anode Catalyst Layer Porosity on the Performance of a Direct Formic Acid Fuel cell. 2012, 62, 36-41.Lam, S., Bixby, M.M., and Rice, C.A., Optimization of Mass Transport within Direct Formic Acid Fuel Cell Catalyst Layer via Pore Formers.Khandavalli, S., Park, H.J., Kariuki, N.N., Myers, J.D., Stickel, J.J., Hurst, K., Neyerlin, C.K., Ulsh, M., and Mauger, A.S., Rheological Investigation on the Microstucture of Fuel Cell Catalyst Inks. 2018, 10, 50.

Pd Nanoparticle Size Effect of Anodic Catalysts on Direct Formic Acid Fuel Cell Initial Performance: Development of a Mathematical Model and Comparison with Experimental Results

AbstractDirect Formic Acid Fuel Cell (DFAFC) is considered as a promising liquid fuel cell. Here, the effect of palladium particle size (dPd) of anodic DFAFC catalysts on initial power density was studied. The number of electrochemically available Pd atoms on the surface of Pd nanocrystallites in the anodes were determined experimentally. The cathode potential as a function of the current density has been measured. The mathematical model describing the effect of dPd on DFAFC performance has been developed. It was assumed that: (i) Pd crystallites have shape of cuboctahedron, (ii) Pd atoms lying on edges and corners are inactive, (iii) The activity of Pd atoms lying on crystallite (111) and (100) facets do not change with dPd. The mathematical model describes well the effect of current density and dPd on fuel cell voltage and power density. The model predicts that maximum power density is reached at dPd=2.4 nm.

Investigation on a Novel Direct Liquid Fuel Cell Feeding on Oxalyl Dihydrazide

Direct liquid fuel cells (DLFCs) are promising candidates for portable applications, because they have high energy density which means long runtime, high energy efficiency, and don’t require time-consuming recharging. At present, several types of DLFCs have been invented such as Direct Methanol Fuel Cells (DMFCs), Direct Formic Acid Fuel Cells (DFAFCs), Direct Sodium Borohydride Fuel Cells (DSBFCs), Direct Hydrazine Fuel Cells (DHFCs) and so on. In this work, we propose a novel direct liquid fuel cell feeding on oxalyl dihydrazide which presents as solid power at room temperature and can be easily dissolved in alkali solution, without any emitting toxic gases. Several potential anode catalysts such as Pt/C, PtRu/C and Au/C are evaluated using a three-electrode cell. The results show that Pt/C is more suitable for the electrochemical oxidation of oxalyl dihydrazide than PtRu/C and Au/C. Using Pt/C as anode catalyst, we designed and fabricated two types of Membrane Electrode Assemblies (MEAs) of different structure, one-catalyst-layer MEA (MEA-1CL) and two-catalyst-layer MEA (MEA-2CL). The single cell tests show MEA-2CL obtain higher I–V performance.

Indirect Formic Acid Fuel Cell Based on a Palladium or Palladium‐Alloy Film Separating the Fuel Reaction and Electricity Generation

AbstractAn indirect fuel cell concept is presented herein, where a palladium‐based membrane (either pure Pd with 25 μm thickness or Pd75Ag25 alloy with 10 μm thickness) is used to separate the electrochemical cell compartment from a catalysis compartment. In this system, hydrogen is generated from a hydrogen‐rich molecule, such as formic acid, and selectively permeated through the membrane into the electrochemical compartment where it is then converted into electricity. In this way, hydrogen is generated and converted in situ, overcoming the issues associated with hydrogen storage and presenting chemical hydrogen storage as an attractive and feasible alternative with potential application in future micro‐ and macro‐power devices for a wide range of applications and fuels.

From CO2 to Formic Acid Fuel Cells

Formic acid is a liquid, safe, and energy-dense carrier for fuel cells. Above all, it can be sustainably produced from the electroreduction of CO2. The formic acid market is currently saturated, an...

Optimization of Mass Transport within Direct Formic Acid Fuel Cell Catalyst Layer via Pore Formers

Direct formic acid fuel cells (DFAFC) offer a potentially sustainable alternative to the batteries in portable devices due to their higher charge capacity, high efficiency, and smaller size. However, due to the two-phase flow in the anode catalyst layer and the small pore size between agglomerates in the catalyst layer (~20 nm), mass transport limitations plague the performance of the DFAFC. To maximize the performance, the two-phase transport of the reactant (formic acid) and the product (carbon dioxide) must be optimized. The incorporation of a pore forming template during catalyst layer fabrication and subsequent removal can increase the porosity between catalyst/ionomer agglomerates and enhance mass transport into and out of the anode catalyst layer.In 2002, a 3.4x enhancement in current density at 60°C of 3.4x was reported due to pretreatment with 1M methanol.[1] The methanol swelled the anode catalyst layer thereby enhancing mass transport. This methanol pretreatment was found to be only temporal. In 2012, the addition of the pore forming template lithium carbonate (Li2CO3) has been shown to form ~10 mm voids through the thickness of the ~10 mm catalyst layer after acid leaching out the Li2CO3.[2] The formic acid electrooxidation charge transfer resistance was reduced for 17.5 wt% pore former additions, at the detriment of the catalyst layer’s triple-phase boundaries.The present study aims to increase the nano-range porosity of the anode catalyst layer to enhance two-phase flow, while maintaining the integrity of the triple-phase boundaries. The alternative templating agent is magnesium oxide (MgO) with an average size of only ~50 nanometers. MgO has been shown to increase mass transport of methanol.[3] The current work shows improved catalytic activity due to the increase in the porosity. Ha, S.; Rice, C.A.; Masel, R.I. and Wieckowski, A., Methanol conditioning for improved performance of formic acid fuel cells. 2002, 112, 655-659.Bauskar, A.S. and Rice, C.A., Impact of anode catalyst layer porosity on the performance of a direct formic acid fuel cell. 2012, 62, 36-41.Huang, Q.; Jiang, J.; Chai, J.; Yuan, T.; Zhang, H.; Zou, Z.; Zhang, X. and Yang, H., Construction of porous anode by sacrificial template for a passive direct methanol fuel cell. 2014, 262, 213-218.

Effect of the Pore Structure of the Gas Diffusion Electrode on the Power Generation and Mass Transport Properties of Direct Formic Acid Fuel Cell

Direct Formic Acid Fuel Cell has been attracted match attention due to its higher power density and lower crossover. In order to improve their performance, we have tried to improve the mass transport in the anode electrode since a large amount of carbon dioxide is emitted by the electrochemical reaction. For the anode electrode, diffusion layer, such as carbon cloth and carbon paper used in the polymer electrolyte fuel cell, is commonly used in direct formic acid fuel cell. These diffusion layers were suitable for the gas supplying; however, it is not clear that these diffusion layers were also suitable for direct liquid fuel cell using liquid fuel. Moreover, the suitable pore structure of diffusion layer for the direct liquid fuel cell is also unknown. In this context, we fabricated the gas diffusion layer having different pore diameter, thickness and porosity using same manner and material in order to evaluate the effect of the pore structure of diffusion layers on the power generation characteristics and mass transport properties in direct formic acid fuel cell. The diffusion layers having 0.03-0.1 mm in average pore diameter, 60-90% in porosity, and 0.1-0.3 mm in thickness could be successfully fabricated using the purchased carbon fiber. The direct formic acid fuel cells using different diffusion layers for anode were fabricated and evaluated the i-V performance and crossover flux. It was found that the big pore can enhance the fuel feed rate to the anode catalyst layer under low current density (low CO2 emission), on the other hands, it did not contribute to the improvement of the fuel feed rate to the catalyst layer under higher current regions (high CO2 emissions). Small pore showed the counter trend. These results implies that the liquid feed and CO2 emissions is closely related the pore properties of diffusion layers, therefore, it is suggested that diffusion layer having suitable pore properties for direct liquid fuel cell is desired.

Performance of Nb0.8Zr0.2 Layer-Modified AISI430 Stainless Steel as Bipolar Plates for Direct Formic Acid Fuel Cells

To improve the interfacial conductivity and corrosion resistance of AISI430 stainless steel (430SS) as bipolar plates for direct formic acid fuel cells (DFAFCs), a Nb0.8Zr0.2 layer has been successfully synthesized via the pulsed laser deposition (PLD) technique on the surface of 430SS. This Nb0.8Zr0.2 layer is smooth, uniform, and comparatively compact without any surface flaw and micropore. Investigation under the simulated anodic environment of DFAFCs (0.05 M H2SO4 + 2 ppm HF + 10 M HCOOH at 70 °C) shows that the corrosion resistance of 430SS is obviously ameliorated after the PLD modification. In addition, the interfacial contact resistance of Nb0.8Zr0.2-430SS (6.0 mΩ cm2) is much smaller than that of bare 430SS (151.3 mΩ cm2) at the clamping force of 140 N cm−2. Besides, different from the highly increased interfacial contact resistance of bare 430SS, the Nb0.8Zr0.2-430SS shows a minor increase resistance after potentiostatic tests in simulated anodic environment of DFAFCs.

Optimization of Mass Transport within Direct Formic Acid Fuel Cell Catalyst Layer via Pore Formers

Direct formic acid fuel cells (DFAFC) offer a potentially sustainable alternative to the batteries in portable devices due to their higher charge capacity, higher efficiency, and smaller size. However, due to the two-phase flow in the anode catalyst layer and the small pore size between agglomerates in the catalyst layer (~20 nm), mass transport limitations plague the performance of the DFAFC. To maximize the performance, the two-phase transport of the reactant (formic acid, liquid) and the product (carbon dioxide, gas) must be optimized. By incorporating 15 and 25 wt% MgO, the electrochemical surface area (ECSA) of the catalyst layer increased from 21.8 cm2 g-1 to 62.7 and 85.8 cm2 g-1, respectively. Furthermore, at higher potentials the porous catalyst layers improved cell performance by 86%. These improvements in ECSA and cell performance are possibly due to an enhancement of the triple-phase boundary.

Stable and Efficient PtRu Electrocatalysts Supported on Zn-BTC MOF Derived Microporous Carbon for Formic Acid Fuel Cells Application.

Highly efficient, well-dispersed PtRu alloy nanoparticles supported on high surface area microporous carbon (MPC) electrocatalysts, are prepared and tested for formic acid oxidation reaction (FAOR). The MPC is obtained by controlled carbonization of a zinc-benzenetricarboxylate metal-organic framework (Zn-BTC MOF) precursor at 950°C, and PtRu (30 wt.%) nanoparticles (NPs) are prepared and deposited via a polyol chemical reduction method. The structural and morphological characterization of the synthesized electrocatalysts is carried out using powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), an energy dispersive X-ray (EDX) technique, and gas adsorption analysis (BET). The FAOR performance of the catalysts is investigated through cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). A correlation between high electrochemical surface area (ECSA) and high FAOR performance of the catalysts is observed. Among the materials employed, Pt1Ru2/MPC 950 with a high electrochemical surface area (25.3 m2 g−1) consequently showed superior activity of the FAOR (Ir = 9.50 mA cm−2 and Jm = 2,403 mA ) at room temperature, with improved tolerance and stability toward carbonaceous species. The superior electrochemical performance, and tolerance to CO-poisoning and long-term stability is attributed to the high surface area carbon support (1,455 m2 g−1) and high percentage loading of ruthenium (20 wt.%). The addition of Ru promotes the efficiency of electrocatalyst by offering FAOR via a bifunctional mechanism.

Palladium-Based Nanostructures Supported on Graphene Oxide for Formic Acid Electro-Oxidation

Increments of significant Green House Gases emissions, GHG, due to persistent policies on continuing fossil fuel burning has led, in return, to more research on conversion, storage and distribution of sustainable energy sources. Direct Liquid Fuel Cells (DLFCs) coupled with Pd-based nanoparticles (PdNPs), as renewable energy sources, are capable of attaining relatively high energy conversion efficiencies, safety of operation and dependability; together, they can be applied to portable devices and transport means. For example, Direct Formic Acid Fuel Cells (DFACs) are used for these applications. This work deals with the synthesis of Pd-based electrocatalysts through a combustion method. Electrocatalysts were characterized by XRD and SEM. Further, the ensuing electrochemical characterization was carried out by means of the electrocatalysts activation, CO adsorption/oxidation and formic acid electro-oxidation. Figure 1