Direct Borohydride Fuel Cell Research Articles

Polyvinyl Alcohol Anion Exchange Resin Composite Membrane with Co@Cu Core–Shell Particles for Direct Borohydride Fuel Cell Applications

A polyvinyl alcohol anion exchange resin composite membrane, functionalized with Co and Cu ions, is reported for use in direct borohydride fuel cells (DBFCs). The CoCu-functionalized membrane has a 30.5% lower fuel permeability than that of a blank membrane. Meanwhile, the cell performance of the DBFC can also be improved by employing the CoCu-functionalized membrane, reaching a maximum power density of 304 mW·cm–2 at 60 °C. High-resolution fluorescence images directly demonstrate the formation of Cu/Co core–shell structure microparticles in the CoCu membrane, which not only reduces the Co content but also increases the active surface area of Co species in CoCu-functionalized membranes, resulting in the improvement of cell performance.

Lattice strain controlled Ni@NiCu efficient anode catalysts for direct borohydride fuel cells.

We successfully fabricated a novel tensile lattice strained Ni@NiCu catalyst with a popcorn-like morphology, which is composed of a crystalline Ni core and a NiCu alloy shell. It exhibits outstanding catalytic activity, selectivity, and stability towards borohydride electrooxidation. Moreover, a direct borohydride fuel cell (DBFC) with a Ni@NiCu anode can deliver a power density of 433 mW cm-2 and an open circuit voltage of 1.94 V, much better than the performances of DBFCs employing other anode catalysts reported in the literature. This could be attributed to the fact that the tensile lattice strain generated by the introduction of Cu leads to a rise in the d-band center of the Ni metal and promotes the final B-H decoupling, which is the rate-determining step in the borohydride oxidation reaction, thus improving remarkably the catalytic performances of Ni@NiCu.

Integrated cathode with in-situ grown MnCo2O4/NC/MnO2 catalyst layer for alkaline liquid fuel cells

This study was conducted to develop new fabrication techniques and achieve improved performance of the cathode in liquid fuel cells. An integrated electrode with a sandwich-structured MnCo2O4/NC/MnO2 catalyst was prepared by in-situ growth on nickel foam. The resulting integrated electrode was tested as the cathode of the alkaline direct methanol fuel cell (DMFC) and direct borohydride fuel cell (DBFC). The data indicated peak power density of 12.22 mW cm−2 for DMFC, and 33.65 mW cm−2 for DBFC. The in-situ growth of the MnCo2O4/NC/MnO2 catalyst layer, without an organic binder, indicated a superior catalytic activity to that of MnCo2O4 and MnCo2O4/NC. Moreover, stability test conducted at a constant-current discharge of 10 mA cm−2 for the integrated cathode-based DBFC revealed excellent stability for about 350 h. Compared to that of traditional cathode prepared by doctor-blade method, traditional cathode showed a significantly diminished discharge voltage. Thus, the highly dispersed nanocatalysts and the macroporous nickel foam accelerated the intrinsic catalytic activity and mass transfer in the cathode. This work provides a new strategy for the preparation and structure optimization of fuel cell electrodes.

Cobalt-based N-doped bamboo-like graphene tubes with enhanced durability for efficient oxygen reduction reaction in direct borohydride fuel cell

Exploring efficient non-precious metal cathode catalysts is attracting ever-increasing interest in the development of direct borohydride fuel cell (DBFC). Herein, a cobalt-based nitrogen-doped bamboo-like graphene tube (Co-NGT) is prepared as an efficient cathode catalyst. The Co-NGT consists of bamboo-like graphene tubes (40–130 nm in diameter and ∼10 μm in length), as well as cobalt nanoparticles (50–100 nm in diameter) confined in the graphene tubes. The Co-NGT shows an onset reduction potential of 0.964 V and an almost four-electron pathway towards oxygen reduction reaction, as well as a negative shift of 8 mV in half-wave potential after 10,000 CV cycles. The Tafel slope of the Co-NGT catalyst is 47 mV decade−1, which is by ca. 37.8 mV decade−1 smaller than for Pt/C. A DBFC using the Co-NGT cathode yields the biggest power density of 453 mW cm−2 at 60 °C and a life span of over 120 h. The excellent electrocatalytic properties and superior durability of Co-NGT catalyst arise from the highly graphitized NGT, providing strong interaction with Co nanoparticles and mitigating the agglomeration of Co nanoparticles. Our study guides for composition and structural design of high-efficient cathode catalysts of DBFC.

Electrodeposited NiCu nanoparticles for the borohydride oxidation reaction: Effect of Cu on the activity and stability of Ni upon surface oxidation

Development cost-effective and stable electrocatalysts for the borohydride oxidation reaction (BOR) is mandatory for the deployment of the direct borohydride fuel cells (DBFC). Ni electrocatalysts have recently been shown to outperform noble-metal (Pt, Pd, Au) catalysts at low BOR overpotentials, but their activity largely depends on the state of the Ni surface with metallic Ni demonstrating the highest activity. Here, bimetallic NiCu nanoparticles of different compositions were prepared, which demonstrate high BOR activity comparable to Ni nanoparticles in the metallic state of their surface and allow to overcome in considerable extent the negative issues related to inevitable surface passivation.

Carbon Coated and Nitrogen Doped Hierarchical NiMo-Based Electrocatalysts with High Activity and Durability for Efficient Borohydride Oxidation

Sodium borohydride is a promising candidate as hydrogen storage material. The direct borohydride fuel cell (DBFC) as an energy conversation device has attracted intensive attention owing to the low theoretical potential of borohydride oxidation reaction (BOR, -1.24 V vs SHE) on the anode. In this paper, the hierarchical sea urchin-like NiMoN@NC coated by thin carbon layer with optimal BH4- adsorption characteristic was synthesized as a superior electrocatalyst toward BOR. In 1 M NaOH-0.05 M NaBH4, the BOR working potentials are only -55 and 44 mV at the current densities of 10 and 200 mA cm-2 on NiMoN@NC, respectively. Furthermore, the membrane-free DBFC using NiMoN@NC as anodic electrocatalyst shows a maximum power density of 67 mW cm-2 at room temperature with appreciative stability. This well-designed carbon coated and nitrogen doped transition-metal material with hierarchical nano/microstructure as a highly efficient electrocatalyst shows promising potential and bright prospects in electrocatalysis research and practical application for energy conversion systems of DBFC.

The catalytic oxidation properties for BH4− and electrochemical properties of the Ag-decorated AB5-type hydrogen storage alloy

Anode catalysts for direct borohydride fuel cells (DBFCs) are one of the key factors controlling the performance of such cells. Hydrogen storage alloys are efficient and inexpensive DBFC anode catalysts. However, when hydrogen storage alloys are used as DBFC anode catalysts, their catalytic oxidation capacity is weakened due to their easy passivation in alkaline electrolytes. In order to improve the catalytic oxidation ability of AB5-type hydrogen storage alloy, Ag-decorated AB5-type alloy catalysts with different Ag contents were prepared by vibration ball milling method in this study. The microstructures, catalytic properties on BH4− and electrochemical properties of pure Ag, AB5-type and Ag-decorated AB5-type alloy samples were studied in detail. The results show that the Ag-decorated AB5-type alloys are composed of a single LaNi5 phase. Some of Ag powders cover the surface of the AB5-type alloy particles. Among the Ag-decorated AB5-type alloys, the Ag-decorated AB5-type alloy with an Ag content of 2 wt.% exhibits the best electrochemical performance and catalytic performance for BH4−. Its maximum discharge time in 6 M KOH solution is 303 min, which is 43 min longer than that of the AB5-type alloy. The number of electrons transferred by the Ag-decorated AB5-type alloy with 2 wt.% is the largest, reaching 1.45. The improvement of the electrochemical and catalytic properties of the alloy is mainly attributed to the proper Ag powders coating on the surface of the AB5-type alloy particles, which protects the electrode from oxidation and corrosion, and enhances the conductivity of the alloy electrode.

Direct borohydride fuel cells: A selected review of their reaction mechanisms, electrocatalysts, and influence of operating parameters on their performance

Direct borohydride fuel cells (DBFC) oxidize an easily-stored energy-dense borohydride fuel (sodium borohydride: NaBH 4 ), that in theory reacts ca . 400 mV below H 2 and produces 8 electrons per BH 4 - anion. However, the borohydride oxidation reaction (BOR) does not fully meet these promises in practice: the electrocatalyst nature, structure and state-of-surface, and the operating conditions (pH, BH 4 - concentration, temperature, fluxes) noticeably influence the BOR kinetics and mechanism. Nickel and platinum-based catalysts both have assets for the BOR. DBFCs can only yield decent performance if their separator combines high ion-conductivity and efficient separation of the reactants; cation-exchange membranes, anion-exchange membranes, bipolar membranes and porous separators all have their own advantages and drawbacks. Besides the anode, the choice of separator must consider the DBFC cathode reaction, where oxygen (usually from air) or hydrogen peroxide are reduced, provided adapted catalysts are used. All these aspects drive the DBFC performance and stability/durability. • The BOR kinetics/mechanism strongly depends on the catalyst and operating parameters. • Metallic nickel is highly efficient at low potential values but leads to high H 2 escape. • Platinum leads to fast kinetics of the H 2 production from BH 4 - and fast H 2 oxidation. • Depending on the membrane/separator, DBFC must employ BH 4 - tolerant cathodes. • The morphology of the electrode, diffusion medium and bipolar plate channels impact mass-transport hence DBFC performance.

Selective Borohydride Oxidation Reaction on Nickel Catalyst with Anion and Cation Exchange Ionomer for High‐Performance Direct Borohydride Fuel Cells (Adv. Energy Mater. 16/2022)

Borohyride Fuel Cells In article number 2103539, Andreas Züttel and co-workers develop a facile synthesis method for a nickel catalyst and ionomer composite for replacing palladium catalysts in direct borohydride fuel cells (DBFCs). The DBFC operates with a liquid fuel (anode: sodium borohydride solution, cathode: hydrogen peroxide solution) to generate electricity.

Selective Borohydride Oxidation Reaction on Nickel Catalyst with Anion and Cation Exchange Ionomer for High‐Performance Direct Borohydride Fuel Cells

AbstractDirect borohydride fuel cells (DBFCs) operate with liquid H2O2 and a high‐energy‐density NaBH4 solution. A facile, direct synthesis method using a non‐noble nickel catalyst for the DBFC anode is shown. The complex anode reaction with an anion‐exchange ionomer (AEI) and a cation‐exchange ionomer (CEI) is evaluated in half‐cell and single‐cell configurations. The ionomer type produces high (AEI) or low local pH (CEI) at the active site of the catalyst in the single‐cell configuration, generating different catalytic reactions. The performance of the nickel catalyst is compared to that of a palladium catalyst. The selective catalytic activities for the borohydride oxidation reaction and hydrogen oxidation reaction are the key parameters for achieving good performance. Furthermore, fuel utilization and H2 evolution measurement in a single‐cell configuration provide more information on the complex anode reaction in the DBFC. The nickel catalyst with CEI on nickel foam (NiF@CEI‐Ni) shows the highest DBFC peak power density (0.59 W cm−2) with a non‐noble metal anode catalyst.

Hierarchical leaf-shaped Ni@Zn bimetallic catalyst with high stability and selectivity for borohydride oxidation

The bimetallic nickel zinc catalyst (Ni@Zn) with hierarchical morphology has been fabricated successfully by an ultrafast and simple synthesis strategy. Unique hierarchical morphology of the catalyst composes of honeycomb arrays, which are formed by Ni shell/Zn core leaves. This Ni@Zn possesses excellent catalytic activity, stability, and selectivity towards borohydride oxidation reaction (BOR). Moreover, a direct borohydride fuel cell (DBFC) with the Ni@Zn/C anode delivers a peak power density of 180.3 mW cm−2 at 298 K. The outstanding performances originate from the increase of electroactive surface area, enhancement of reactants adsorption, and the inhibition of Ni oxidation, which are attributed to its unique hierarchical structure and the introduction of Zn. This study may provide important inspiration for developing efficient noble-metal-free catalysts for DBFC.

Porous Ni-Cu Alloy Dendrite Anode Catalysts with High Activity and Selectivity for Direct Borohydride Fuel Cells.

A porous Ni-Cu alloy dendrite catalyst covered by Ni nanoparticles (Ni-np@NC) has been fabricated by an ultrafast and controllable strategy. The research results show that the morphology of the Ni-Cu alloy depends strongly on the Cu2+concentration. Moreover, the Ni-np@NC catalyst demonstrates excellent selectivity and activity toward the borohydride oxidation reaction (BOR). Furthermore, on the Ni-np@NC catalyst electrode, the overpotential merely requires 169 mV at a current density of 10 mA cm-2 for BOR, and the fuel efficiency may reach 70%. The direct borohydride fuel cell using the Ni-np@NC/C anode can export a maximum power density of 218 mW cm-2, much higher than that using the noble-based anode reported in the literature. The remarkable enhancement of Ni-np@NC catalyst performances is on the back of the unique morphology of porous dendrite covered by nanoparticles and the introduction of Cu.

Design of Promising Green Cation-Exchange-Membranes-Based Sulfonated PVA and Doped with Nano Sulfated Zirconia for Direct Borohydride Fuel Cells.

The direct borohydride fuel cell (DBFC) is a low-temperature fuel cell that requires the development of affordable price and efficient proton exchange membranes for commercial purposes. In this context, super-acidic sulfated zirconia (SO4ZrO2) was embedded into a cheap and environmentally friendly binary polymer blend, developed from poly(vinyl alcohol) (PVA) and iota carrageenan (IC). The percentage of SO4ZrO2 ranged between 1 and 7.5 wt.% in the polymeric matrix. The study findings revealed that the composite membranes’ physicochemical features improved by adding increasing amounts of SO4ZrO2. In addition, there was a decrease in the permeability and swelling ratio of the borohydride membranes as the SO4ZrO2 weight% increased. Interestingly, the power density increased to 76 mW cm−2 at 150 mA cm−2, with 7.5 wt.% SO4ZrO2, which is very close to that of Nafion117 (91 mW cm−2). This apparent selectivity, combined with the low cost of the eco-friendly fabricated membranes, points out that DBFC has promising future applications.

Triethanolamine as an efficient electrolyte additive for borohydride electrooxidation on Ni based catalyst

As a non-noble metal, nickel (Ni) is considered as an ideal alternative of noble metal catalysts for borohydride electrooxidation in the direct borohydride fuel cell (DBFC). In this work, triethanolamine (TEA) was employed as additive in electrolyte to improve the performance of Ni based catalyst for borohydride electrooxidation. The cyclic voltammetry measurement showed that the peak current density of oxidation peak for borohydride electrooxidation after 10 cycles remained 59% of that of the first cycle when 0.108 mol·L-1 TEA was added. As a contrast, the oxidation peak of the tenth cycle decreased by 99.3% when TEA was absent. The electrochemical impedance spectra (EIS) showed that TEA could significantly decrease the charge transfer resistance for borohydride electrooxidation on the Ni electrode. Chronoamperometry (CA) result indicated the anodic current could be also enhanced by adding TEA. More importantly, we believe TEA can also be employed in various kinds of Ni based catalysts for borohydride electrooxidation.

Development of Bimetallic PdNi Electrocatalysts toward Mitigation of Catalyst Poisoning in Direct Borohydride Fuel Cells

Development of Bimetallic PdNi Electrocatalysts toward Mitigation of Catalyst Poisoning in Direct Borohydride Fuel Cells

Novel Crosslinked Sulfonated PVA/PEO Doped with Phosphated Titanium Oxide Nanotubes as Effective Green Cation Exchange Membrane for Direct Borohydride Fuel Cells.

A direct borohydride fuel cell (DBFC) is a type of low temperature fuel cell which requires efficient and low cost proton exchange membranes in order to commercialize it. Herein, a binary polymer blend was formulated from inexpensive and ecofriendly polymers, namely polyethylene oxide (PEO) and poly vinyl alcohol (PVA). Phosphated titanium oxide nanotube (PO4TiO2) was synthesized from a simple impregnation–calcination method and later embedded for the first time as a doping agent into this polymeric matrix with a percentage of 1–3 wt%. The membranes’ physicochemical properties such as oxidative stability and tensile strength were enhanced with increasing doping addition, while the borohydride permeability, water uptake, and swelling ratio of the membranes decreased with increasing PO4TiO2 weight percentage. However, the ionic conductivity and power density increased to 28 mS cm−1 and 72 mWcm−2 respectively for the membrane with 3 wt% of PO4TiO2 which achieved approximately 99% oxidative stability and 40.3 MPa tensile strength, better than Nafion117 (92% RW and 25 MPa). The fabricated membrane with the optimum properties (PVA/PEO/PO4TiO2-3) achieved higher selectivity than Nafion117 and could be efficient as a proton exchange membrane in the development of green and low cost DBFCs.

Insights into the borohydride electrooxidation reaction on metallic nickel from operando FTIRS, on-line DEMS and DFT

Direct Borohydride Fuel Cells (DBFCs) are considered as promising power sources for portable and mobile applications. Their advantages are high theoretical energy density, and high theoretical cell voltage. Metallic Ni has recently emerged as a promising electrode material for DBFCs. In this work we combine electrochemical, operando Fourier-transform infrared spectroscopy (FTIRS), and online differential electrochemical mass spectrometry (DEMS) measurements with density functional theory (DFT) calculations to advance the understanding of the borohydride oxidation reaction on Ni.

(Invited) Electrodeposited Ni-Based Electrodes for High-Performance Borohydride Oxidation Reaction

Pt-group metal (PGMs) catalysts are widely employed for the borohydride oxidation reaction (BOR) in direct borohydride fuel cell anodes, however, they have significant drawbacks. PGMs are not efficient for the BOR; they promote non-negligible hydrogen evolution reaction (HER) for E < 0 V vs RHE, allow associated H2 escape that is detrimental to cell operation, and suffer non-negligible poisoning by BHx,ad intermediates (1, 2). Better BOR catalysts should combine poor HER activity and high BOR activity, which seems unfeasible with PGMs. Nickel-based electrodes, widely-used for hydrogen reactions in alkaline environment (3), were recently demonstrated very active for the BOR at low overpotential values, if their state of the nickel surface is tightly controlled and maintained as metallic (4).The present contribution will present BOR mechanism investigation at reduced (metallic) Ni electrodes, using a combination of various electrokinetic measurements, differential electrochemical mass spectrometry (DEMS), Fourier-transform infrared spectroscopy (FTIR), Density Functional Theory (DFT) calculations and microkinetic modelling. The BOR mechanism differs between metallic Ni and PGM surfaces: metallic Ni is less active for the HER (due to a stronger H adsorption on Ni compared to Pt) and less prone to BHx,ad poisoning (due to a weaker adsorption on Ni compared to Pt) without compromising its BOR activity. Cumulatively, these effects account for the higher performance of reduced Ni surfaces at low potential values. The contribution will also highlight how electrodeposited Ni electrodes have been successfully prepared, using various substrates compatible with their implementation in a direct borohydride fuel cell (DBFC). Very open and carbon-free structures like Ni-felts (NFT), have enabled outstanding performance in DBFC conditions, should it be with a cation-exchange membrane (in Na+ form) (5) or a bipolar interface (6), or even anion-exchange membranes. The key in such developments is the proper preparation of the Ni-felt support, so that it essentially presents a high-surface-area metallic surface (Figure 1), stable long enough to be mounted in the fuel cell fixture. Acknowledgments This work has been performed in the frame of the MobiDiC project, funded by the French National Research Agency (ANR, grant # ANR-16-CE05-0009-01) and the DGA. References P.-Y. Olu, A. Bonnefont, G. Braesch, V. Martin, E. R. Savinova and M. Chatenet, J. Power Sources, 375, 300 (2018).G. Braesch, A. Bonnefont, V. Martin, E. R. Savinova and M. Chatenet, Electrochim. Acta, 273, 483 (2018).A. G. Oshchepkov, G. Braesch, A. Bonnefont, E. R. Savinova and M. Chatenet, ACS Catal., 10, 7043 (2020).A. G. Oshchepkov, G. Braesch, S. Ould-Amara, G. Rostamikia, G. Maranzana, A. Bonnefont, V. Papaefthimiou, M. J. Janik, M. Chatenet and E. R. Savinova, ACS Catal., 9, 8520 (2019).G. Braesch, A. G. Oshchepkov, A. Bonnefont, F. Asonkeng, T. Maurer, G. Maranzana, E. R. Savinova and M. Chatenet, ChemElectroChem, 7, 1789 (2020).G. Braesch, Z. Wang, S. Sankarasubramanian, A. G. Oshchepkov, A. Bonnefont, E. R. Savinova, V. Ramani and M. Chatenet, J. Mater. Chem. A, 8, 20543 (2020). Figure 1

Development of effectively costed and performant novel cation exchange ceramic nanocomposite membrane based sulfonated PVA for direct borohydride fuel cells

A direct borohydride fuel cell (DBFC) is a type of low temperature fuel cell, and to commercialize this type of fuel cell, it requires efficient and inexpensive proton exchange membranes. In this study, a binary polymer blend is formulated from inexpensive and ecofriendly polymers such as iota carrageenan (IC) and polyvinyl alcohol (PVA). Zirconiam phosphate (ZrPO4) was synthesized from a simple impregnation — calcination method and later embedded as a doping agent into the polymeric matrix with percentage (1–7.5) wt.%. The novel nanocomposite membranes were evaluated by TGA, DSC, FTIR, XRD and SEM. The oxidative stability and tensile strength of the obtained membranes were enhanced and achieved results better than those of Nafion117 due to an increase in the number of hydrogen bonds formed between the polymer functional groups and oxygen functional groups of ZrPO4with increasing doping concentration. In addition, the borohydride permeability of the membranes decreased with increasing ZrPO4weight percentage, while the ionic conductivity and power density increased to 25.5 mS cm−1 and 66 mW cm−2, respectively, for membrane with 5 wt.% of ZrPO4. The fabricated membrane with the optimum properties (PVA/IC/ZrPO4− 5) can be efficient as a proton exchange membrane towards the development of green and low cost DBFCs.

Synthesis of metallic nanoparticles for heterogeneous catalysis: Application to the Direct Borohydride Fuel Cell

Until now, the fabrication of electrocatalysts to guarantee long life of fuel cells and low consumption of noble metals remains a major challenge. The electrocatalysts based on metals or metal oxides which are used today are limited by the complexity of their synthesis processes and require several steps before depositing the catalysts on the substrate. Herein is described a chemical synthesis process that consists of a single-step synthesis and direct deposition of catalysts nanoparticles such as gold (Au), palladium (Pd) and platinum (Pt) in the thickness of a carbon-fibers-based porous transport layer (PTL). The synthesis process essentially consists of dissolving in the same PGMEA (Propylene glycol methyl ether acetate) solvent a metal precursor (HAuCl4 or PdNO2 or PtCl4) and a homopolymer PMMA (Polymethylmetacrylate), then the metal solution is deposited on the surface of the PTL after cleaning. Special emphasis is made on Pt-based materials. The obtained PTL-supported nanoparticles were firstly characterized by scanning electron microscopy (SEM) to evaluate their morphology, and then X-Ray diffraction (XRD) to observe the crystal phases. To validate the methodology, Pt-coated PTL materials have been used as anode for the borohydride oxidation reaction (BOR) in a direct borohydride fuel cell (DBFC) and compared to a state-of-the-art nickel electrode. There is an optimum loading of platinum (below 0.16 mg Pt / cm2) which constitutes the best compromise between power density and faradic efficiency for the borohydride oxidation reaction (BOR). Thanks to this low Pt loading, hydrogen evolved during the anodic reaction is completely valorized. These electrodes combine the advantages of high-performance with a very low metal loading, hence lowering materials’cost.