Direct Hydrazine Fuel Cells Research Articles

Flexible Anode Catalysts for Direct Hydrazine Fuel Cells

In this study we report a facile approach for fabrication of flexible anode catalysts consisting of a fiber-shaped cobalt deposited on the polyimide (PI) surface for direct hydrazine fuel cells (DHFCs). At first, a thin copper layer has been deposited on the PI surface using electroless metal plating method. Then, the fiber-shaped cobalt coating has been plated by the electrochemical deposition method from the electrolyte containing CoSO4, NaOH and N-(2-Hydroxyethyl) ethylenediamine. For comparison, the cobalt layer that has the smooth structure has been deposited on the flexible PI surface via electroless deposition using morpholine borane as a reducing agent.The morphology and composition of the prepared flexible catalysts have been characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The activity of catalysts has been investigated with respect to the oxidation of hydrazine in an alkaline medium.The results of electrochemical measurements showed that the deposited cobalt layer that has a fiber-shaped structure on the flexible PI surface exhibits an enhanced electrocatalytic activity towards the oxidation of hydrazine as compared with that for cobalt catalyst that has a smooth structure. Moreover, the prepared flexible catalysts seem to be a promising anode material for DHFCs.

Optimistic performance of carbon-free hydrazine fuel cells based on controlled electrode structure and water management

Abstract In this study, we first attempted to discover the optimal configuration of membrane-electrode assemblies (MEAs) used to achieve a high performance of direct hydrazine fuel cells (DHFCs). We have investigated the effect of water management and the electrode thickness on the performance of DHFCs, depending on the hydrophobicity of the gas diffusion layers in the cathode and the catalyst loading in the anode with the carbon-supported Ni, synthesized by a polyol process. With the optimal water management and electrode thickness, the MEA constructed using the as-prepared Ni/C anode catalyst containing the metallic and low oxidative state and ultra-low Pt loading cathode reduced the ohmic resistance and mass transfer limitation in the current-voltage curves observed for the alkaline DHFC, achieving an impressive power performance over 500 mW cm–2.

Surface phosphorization of hierarchically nanostructured nickel molybdenum oxide derived electrocatalyst for direct hydrazine fuel cell

Non-faradaic catalytic decomposition of hydrazine (N2H4) is a vital but underappreciated problem for direct hydrazine fuel cell (DHFC). Herein, a careful study of a nickel molybdenum oxide derived catalyst for N2H4 electrooxidation is reported, with special focus on the method for effectively suppressing non-faradaic decomposition of hydrazine as well as the underlying mechanism. A hierarchically nanostructured catalyst consisting of tiny Ni10Mo alloy nanoparticles dispersed on porous NiMoO nanosheets is synthesized using a simple hydrothermal method followed by reductive annealing treatment. Thus-prepared catalyst shows high activity towards N2H4 electrooxidation, but is entangled with the problematic selectivity towards non-faradaic decomposition of N2H4. Our study find that this problem can be circumvented by a controlled phosphorization method. The resultant catalyst (Ni2P@Ni10Mo/Ni-Mo-O/NF) exhibits exceptionally high activity, excellent durability and nearly 100 % selectivity towards N2H4 electrooxidation. A detailed structural characterization and density functional theory calculations are conducted to understand the phosphorization-induced modification of catalytic property.

Fabrication and evaluation of the performance of Co/CoNiZnAg nanoporous structures as a good candidate for using as anode catalyst in a hydrazine fuel cell

ABSTRACTThe goal of this work is synthesis a new nanoporous Co/CoNiZnAg catalyst by the leaching-galvanic replacement (LGR) process as a highly active and good durable electrocatalyst towards hydrazine oxidation reaction in an alkaline medium. The morphology and elemental analysis of fabricated electrocatalysts were investigated using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), respectively. The results showed that a nanoporous structure for Co/CoNiZnAg coatings. Electrocatalytic activity and stability of these catalysts were estimated using cyclic voltammetry and chronoamperometry methods. The hydrazine oxidation peak current density of this coating towards hydrazine oxidation is higher than that on a smooth silver electrode. The results confirmed that the Co/CoNiZnAg electrocatalyst has a better electrocatalytic activity and enhanced stability. As a result, Co/CoNiZnAg electrocatalyst can be considered a good candidate for using as an anode catalyst in direct hydrazine fuel cells (DHFCs).

Unique Ni Crystalline Core/Ni Phosphide Amorphous Shell Heterostructured Electrocatalyst for Hydrazine Oxidation Reaction of Fuel Cells

It is highly attractive but challenging to develop transition-metal electrocatalysts for direct hydrazine fuel cells (DHzFCs). In this work, a nickel crystalline core@nickel phosphide amorphous shell heterostructured electrocatalyst supported by active carbon (Ni@NiP/C) is developed. Ni@NiP/C with a P/Ni molar ratio of 3:100, Ni@NiP3.0/C, exhibits outstanding catalytic activity for the hydrazine oxidation reaction (HzOR) in alkaline solution, achieving a much better catalytic activity (2675.1 A gNi-1@0.25 V vs RHE) and high stability, as compared to Ni nanoparticles supported on carbon (Ni/C) and Pt/C catalysts. The results indicate that formation of the NiP amorphous shell effectively inhibits the passivation of the Ni core active sites and enhances the adsorption of hydrazine on Ni by improving the adsorption energy, leading to high electrochemical activity and stability of the Ni@NiP3.0/C catalysts for HzOR. The density functional theory calculation confirms the structural and electrocatalytic effect of the core-shell heterostructure on the stability and activity of Ni active sites for HzOR. The unique crystalline core/amorphous shell-structured Ni@NiP/C demonstrates promising potential as an effective electrocatalyst for DHzFCs.

In situ grown nanosheet Ni[sbnd]Zn alloy on Ni foam for high performance hydrazine electrooxidation

The electrocatalyst with cost effective and high performance towards hydrazine electrooxidation is critical to promote the practical application of direct hydrazine fuel cell (DHFC). Herein, an effective approach is developed to study the NiZn alloy as promising hydrazine electrocatalyst by the combined experimental and theoretical investigations. 3D nanosheet NiZn alloy with single α-NiZn phase was successfully synthesized on Ni foam (NF) substrate through the electrodepostion of NiZn alloy and followed electrochemical leaching. The NiZn catalyst exhibits the synergetic capabilities of impressively high activity with a superior current density of 370 mA cm−2 at 0.3 V, excellent durability with a retention rate of 88.7% after 5000 s and almost 100% selectivity for the complete electrooxidation of hydrazine, which is at the top level among the reported electrocatalysts for hydrazine oxidation up to now. The reason for the excellent durability of NiZn catalyst was studied. Specially, first principles calculations were employed to shed light on the catalytic mechanism of high performance NiZn catalyst.

Sulfurization-induced edge amorphization in copper–nickel–cobalt layered double hydroxide nanosheets promoting hydrazine electro-oxidation

The electrocatalytic hydrazine oxidation reaction (HzOR) has drawn extensive attention due to its high energy conversion efficiency and wide applications in hydrazine-assisted water splitting and direct hydrazine fuel cells (DHFC).

Synthesis of nitrogen-doped MnO/carbon network as an advanced catalyst for direct hydrazine fuel cells

Designing a novel, highly efficient earth-abundant, and low cost electrocatalyst is a key for direct hydrazine fuel cell (DHFC) applications. Electrocatalyst plays an eminent role in enhancing the performance of DHFC, a promising tool to produce electricity without CO2 emission. Herein, we report a salt-template based synthesis of manganese oxide (MnO) nanoparticles integrated nitrogen-doped network-like carbon (MnO/N-C) nanocomposites and demonstrated their catalytic performance towards electrochemical oxidation of hydrazine for the first time. The MnO nanoparticles (3.7 nm size) are not only uniformly distributed onto the entire N-C composite surface, but also having enormous porous structure with large active surface area of 885 m2 g−1 and external surface area of 678 m2 g−1, which plays a majestic role in hydrazine oxidation reaction. Interestingly, MnO/N-C nanocomposite displays significantly higher electrocatalytic performance towards hydrazine oxidation than the N-C and MnO catalysts. In addition, the electrocatalytic performance of MnO/N-C nanocomposite appeared even after 3000 cycles, demonstrating an exceptional stability of MnO/N-C catalyst. The improved electrocatalytic efficiency of MnO/N-C nanocomposite originates from the synergetic physicochemical properties of MnO and N-C, which offers large active sites for the catalytic reactions and rapidly facilitates electrolyte diffusion for DHFC applications.

Heteroatom-Doped Carbon Materials for Hydrazine Oxidation.

The key in designing efficient direct liquid fuel cells (DLFCs), which can offer some solutions to society's grand challenges associated with sustainability and energy future, currently lies in the development of cost-effective electrocatalysts. Among the many types of fuel cells, direct hydrazine fuel cells (DHFCs) are of particular interest, especially due to their high theoretical cell voltages and clean emission. However, DHFCs currently use noble-metal-based electrocatalysts, and the scarcity and high cost of noble metals are hindering these fuel cells from finding large-scale practical applications. In order to replace noble-metal-based electrocatalysts with sustainable ones and help DHFCs become widely usable, great efforts are being made to develop stable heteroatom (e.g., B, N, O, P and S)-doped carbon electrocatalysts, the activities of which are comparable to, or better than, those of noble metals. Here, the recent research progress and the advancements made on the development of heteroatom-doped carbon materials, their general properties, their electrocatalytic activities toward the HzOR, and their dopant- and structure-related electrocatalytic properties for the HzOR are summarized. Perspectives on the different directions that the research endeavors in this field need to take in the future and the challenges associated with DHFCs are included.

In situ grown Ni phosphide nanowire array on Ni foam as a high-performance catalyst for hydrazine electrooxidation

Synthesis of high-performance and cost-effective electrocatalysts towards hydrazine electrooxidation is vital to develop the direct hydrazine fuel cell (DHFC) as a viable energy conversion technology. Herein, we report a combined experimental and theoretical study of nickel phosphides (NixP) as promising catalysts for hydrazine electrooxidation. NixP nanowire array supported on a Ni foam (NF) was synthesized by a one-step phosphorization method using hypophosphite as a P-source. Ni12P5 and Ni2P phases are observed as the products of the direct phosphorization of commercial NF under the applied conditions with Ni2P nanoparticles exclusively distributing on the surface of Ni12P5. The NixP/NF catalyst exhibits a synergetic capabilities of exceptionally high activity, excellent durability and nearly 100% selectivity towards the complete electrooxidation of hydrazine in alkaline condition, which is among the best performance reported on hydrazine electrooxidation catalysts. First-principles calculations have been conducted to gain insight into the catalytic mechanism of Ni phosphides towards hydrazine electrooxidation.

On the promotional effect of Cu on Pt for hydrazine electrooxidation in alkaline medium

Pt/C and PtCu/C electrocatalysts with nominal Pt:Cu atomic ratios of 75:25, 50:50, and 25:75 were prepared using N2H4 as reducing agent and carbon black Vulcan XC-72R as support. The obtained materials were physically characterized by X-ray diffraction, Energy-Dispersive X-ray analysis, Transmission Electron Microscopy images, X-ray Photoelectron Spectroscopy (XPS), and Temperature-Programmed Reduction analysis. Cyclic voltammetry, linear sweep voltammetry, and chronoamperometry (TPR) measurements were carried out in a three-electrode glass cell to evaluate the electrochemical activity towards hydrazine electrooxidation in alkaline medium along with single-cell direct hydrazine fuel cell (DHFC) tests. The actual composition of the electrocatalysts evidenced a slightly lower Cu fraction compared to the nominal one. The X-ray diffractograms of the electrocatalysts showed the typical face-centered cubic structure of Pt alloys, with the highest fraction of Cu alloyed to Pt being achieved with the almost equiatomic catalyst. An important fraction of the remaining non-alloyed Cu is in the form of a copper oxide, as evidenced by XPS and TPR measurements. The electrochemical tests evidenced that the coexistence of part of the Cu alloyed with Pt and copper oxide achieved in the PtCu/C electrocatalysts enhances the performance compared to Pt/C. In particular, the optimum formulation is attained by the Pt53Cu47/C electrocatalyst, allowing maximization of the electrocatalytic activity towards hydrazine electrooxidation and the single-cell performance at 60 and 80 °C.

A hybrid hydrazine redox flow battery with a reversible electron acceptor.

Hydrazine is a pollutant with high hydrogen content, offering tremendous possibilities in a direct hydrazine fuel cell (DHFC) as it can be converted into electricity via benign end products. Due to the inner sphere nature of half-cell chemistries, hydrazine cross over triggers parasitic chemistry at the Pt-based air cathode of a state-of-the-art DHFC, overly complicating the already sluggish electrode kinetics at the positive electrode. Here, we illustrate that by altering the interfacial chemistry of the catholyte from inner sphere to outer sphere, the parasitic chemistry can be dissociated from the redox chemistry of the electron acceptor and the hybrid fuel cell can be driven by simple carbon-based cathodes. The reversible nature of an outer sphere catholyte leads to a hybrid fuel cell redox flow battery with performance metrics ∼4 times higher than a Pt-based DHFC-air configuration.

Tree-Bark-Shaped N-Doped Porous Carbon Anode for Hydrazine Fuel Cells.

Metal-free N-doped porous carbon has great potential as a catalyst for hydrazine oxidation in direct hydrazine fuel cells (DHFCs). However, previous studies have reported only half-cell characterization, and the effect of the pore size distribution has not been intensively investigated. Herein, we report the synthesis of highly active, metal-free N-doped carbon (NDC) by controlling the pore size distribution, and for the first time, the effect of the pore size distribution on the anode performance in a DHFC is investigated. As a result, tree-bark-shaped NDC with meso/macroporous (>10 nm) structures exhibit a remarkable power density of 127.5 mW cm-2 in a DHFC.

Tree‐Bark‐Shaped N‐Doped Porous Carbon Anode for Hydrazine Fuel Cells

AbstractMetal‐free N‐doped porous carbon has great potential as a catalyst for hydrazine oxidation in direct hydrazine fuel cells (DHFCs). However, previous studies have reported only half‐cell characterization, and the effect of the pore size distribution has not been intensively investigated. Herein, we report the synthesis of highly active, metal‐free N‐doped carbon (NDC) by controlling the pore size distribution, and for the first time, the effect of the pore size distribution on the anode performance in a DHFC is investigated. As a result, tree‐bark‐shaped NDC with meso/macroporous (>10 nm) structures exhibit a remarkable power density of 127.5 mW cm−2 in a DHFC.

Computational Design of Ni-Zn Based Catalyst for Direct Hydrazine Fuel Cell Catalyst Using Density Functional Theory

Direct Hydrazine Fuel Cell (DHFC) is a promising alternative for the hydrogen fuel cell because hydrazine (N2H4) is much easier to produce and store than hydrogen. Research into DHFC catalyst has shown that use of Ni-Zn compound as catalyst produces higher power density than using pure Ni as catalyst. This paper presents some findings of our investigation on Ni-Zn based catalyst for DHFC applications by using density functional theory (DFT). Multiple configurations of Ni-Zn DHFC catalysts were modeled using DFT. Hydrazine adsorption onto (111) catalyst surface was studied with adsorption energy and density of states (DOS) collected as data and used in analysis. The supercells consist of 4 layers of 4x4 atoms forming the (111) surface, with structure variation for the top 2 layers and the other 2 bottom layers comprised of Ni atoms to simulate the bulk of the electrodes. The adsorption sites used were the top sites, either Zn or Ni atoms. For every structure variation, adsorption on Ni atoms results in lower adsorption energies than on Zn atoms. Increasing concentration of Zn atoms on catalyst surface raises the adsorption energy of hydrazine on Zn atoms. Adsorption energies of hydrazine were higher on every configurations than on pure Ni (111) surface except for one catalyst surface in which Zn concentration was 25% and hydrazine was adsorbed atop a Ni atom. There was also rotation of hydrazine molecule from its usual anti adsorption conformation for that particular configuration.

Ni3S2@Ni foam 3D electrode prepared via chemical corrosion by sodium sulfide and using in hydrazine electro-oxidation

Hydrazine electro-oxidation takes an important role in direct hydrazine fuel cells (DHFCs) and hydrazine electrochemical sensor, but the high cost of precious metal electrode hinders the practical applications of hydrazine electro-oxidation. In this study, an inexpensive 3D electrode of Ni3S2@Ni foam was obtained through a hydrothermal condition using sodium sulfide as corrodent and Ni foam as both substrate and Ni source. The formation mechanism of this Ni3S2 layer was studied through a process analysis based on physical chemistry with assistant of the results from characterizations. The obtained Ni3S2@Ni foam was used as electrode to test its hydrazine electro-oxidation properties in terms of DHFCs and electrochemical sensor. It is found Ni3S2@Ni foam possesses the ability to electro-oxidize hydrazine and Ni3S2 layer leads to increased activity including lower onset potential and higher current. In the aspect of hydrazine electrochemical sensor, the fabricated Ni3S2 layer leads to increased sensitivity and dynamic response property. The results indicate that as-prepared Ni3S2@Ni foam possesses a potential for practical application in hydrazine electro-oxidation, and Ni3S2 is a very promising substitute material for noble metals in hydrazine electro-oxidation. At the same time, with the characterization of the as-prepared Ni3S2@Ni foam electrode on structure, morphology and surface chemical states, the mechanism of the corrosion method as well as enhanced properties were investigated.

High Performance of Carbon-Supported Nickel-Platinum Nanocatalysts for Hydrazine Electrooxidation in Alkaline Electrolyte

Hydrazine exhibits many advantages as fuel for alkaline fuel cells. The products from the Direct Hydrazine Fuel Cells (DHFCs) are nitrogen and water that are neither harmful nor contain carbon. Furthermore, the DHFCs theoretical voltage is +1.56 V and DHFCs can operate at near-ambient temperatures (40-80oC) (1, 2). Pt is an effective electrocatalyst for the hydrazine oxidation reaction (HzOR), as is Ni, but at higher hydrazine concentration and higher temperatures (3-5). In previous works, the combination of Ni with its group metals (Pd and Pt) has been used as electrocatalysts for HzOR at room temperature, but the role of each metal in the composite catalyst remains unclear (4). In order to investigate the function of each metal in the electrocatalyst toward the HzOR, carbon-supported Ni-Pt nanoparticles were synthesized with 15, 33 and 66 wt% Ni content on Pt/C, using the a thermal decomposition method (6). The materials were characterized by TEM and XRD, and their electrocatalytic activities analyzed by Cyclic Voltammetry and Chronoamperometry in 1.0 mol L-1 KOH in the presence or absence of 0.1 mol.L-1 N2H4, at 25 oC. The diffraction patterns (Figure 1) clearly show the peaks of metallic Pt and the coexistence of two phases: NiO and Ni(OH)2., without shift in 2-theta of the diffraction peaks. These are evidences that the Ni-oxide phase is segregated from the Pt phase; the electrocatalyst structure seems to be formed by clusters/islands of Ni-oxide on the surface of the Pt/C nanoparticles, instead of Ni-Pt alloys. The average crystallite sizes of Pt resulted in 3.3 nm and the Ni(OH)2 and NiO crystallite sizes are estimated to be 4.0 nm and 3.4 nm, respectively. Furthermore, there were no significant changes in the average sizes with the increasing of Ni content. The cyclic voltammograms of Figure 2 indicate the following order of activity: 15% > 33% > pure Pt/C > 66% > pure NiO, thus, resulting in an optimal value around 15 wt.% of Ni. These results show an interplay of Ni and Pt atoms for the HzOR, and this seems to be a bifunctional effect, in which the Ni atoms provide OH species for the electrooxidation of the adsorbed hydrogen atoms on the Pt surface, at low potentials. Acknowledgements: The authors would like to thank FAPESP, CAPES/COFECUB, CNPq and CNRS for financial support.

ChemInform Abstract: Anode Catalysts for Direct Hydrazine Fuel Cells: From Laboratory Test to an Electric Vehicle.

AbstractNanocrystalline Ni87Zn13 main phase plus varying amounts of a minor ZnO phase as a highly active electrocatalyst for hydrazine hydrate (HH) fuel cell applications are prepared by ball milling of the metal nitrates and carbon black (500 rpm, 2.5 h) followed by thermal reduction in 7% H2/N2 (450 °C, 4 h).

Anode catalysts for direct hydrazine fuel cells: from laboratory test to an electric vehicle.

Novel highly active electrocatalysts for hydrazine hydrate fuel cell application were developed, synthesized and integrated into an operation vehicle prototype. The materials show in both rotating disc electrode (RDE) and membrane electrode assembly (MEA) tests the world highest activity with peak current density of 16,000 A g(-1) (RDE) and 450 mW cm(-2) operated in air (MEA).

Anode Catalysts for Direct Hydrazine Fuel Cells: From Laboratory Test to an Electric Vehicle

AbstractNovel highly active electrocatalysts for hydrazine hydrate fuel cell application were developed, synthesized and integrated into an operation vehicle prototype. The materials show in both rotating disc electrode (RDE) and membrane electrode assembly (MEA) tests the world highest activity with peak current density of 16 000 A g−1 (RDE) and 450 mW cm−2 operated in air (MEA).