Direct hydrazine-hydrogen peroxide fuel cell using carbon supported Co@Au core-shell nanocatalyst

Carbon-supported Co@Au core-shell/C and Au/C nanoparticles are synthesized by a successive reduction method in an aqueous solution and used as the anode and cathode electrocatalysts for the direct hydrazine-hydrogen peroxide fuel cell, respectively. The physical and electrochemical properties of the as-prepared electrocatalysts are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and fuel cell field tests. In this work, the effects of different operation conditions including operation temperature, fuel and oxidant concentration and fuel and oxidant flow rate on the performance of fuel cell are systematically investigated. The experimental results exhibit an open circuit voltage of about 1.79 V and a peak power density of 122.75 mW cm^?2 at a current density of 128 mA cm^?2 and a cell voltage of 0.959 V operating on 2.0 M N₂H₄ and 2.0 M H₂O₂ at 60 °C.     

A possible future fuel cell: the peroxide/peroxide fuel cell

Hydrogen peroxide (H₂O₂) and the reduction/oxidation by‐products of peroxide are non‐toxic to humans and the environment. Simple, low‐concentration hydrogen‐peroxide solutions used as fuel and direct peroxide/peroxide fuel cells (DPPFCs) face significant challenges in the development of a new class of power generators. A power density of 10 mWcm^?2 at a cell potential of 0.55 V have been achieved with a DPPFC composed of carbon‐paper‐supported nickel as the anode catalyst and carbon‐paper PbSO₄ as the cathode catalyst. The catalysts have been prepared by electroless deposition. Using non‐precious metals rather than platinum in our FC makes the cell cost effective comparable to that of PEMFCs. Additionally, as a low‐price fuel, H₂O₂ reduces the cost of this FC. Copyright © 2012 John Wiley & Sons, Ltd.     

Fabrication of a quasi-symmetrical solid oxide fuel cell using a modified tape casting/screen-printing/infiltrating combined technique

To develop the symmetrical electrode materials for solid oxide fuel cells (SOFCs) and to explore the facile cell fabrication technique are both meaningful and of great significance. Here a bi-functional hybrid material LaNi_0.82Fe_0.18O₃ (LNF)/NiO was synthesized by a one-pot citrate method and further used as the quasi-symmetrical electrode catalysts for solid oxide fuel cells (SOFCs). LNF and Ni (reduced NiO) functioned as the cathode/anode catalysts. The La_0.9Sr_0.1Ga_0.8Mg_0.2O₃ (LSGM) based asymmetrical tri-layered substrates were fabricated by a screen-printing assisted co-firing technique. The polarization resistances (Rp) of the infiltrated anode at 700, 650, 600 and 550 °C were only 0.08, 0.12, 0.18 and 0.3 Ω cm², respectively. Comparably, the Rp of the infiltrated cathode were much larger, e.g., 0.18, 0.35, 0.875 and 2.55 Ω cm² at 700, 650, 600 and 550 °C, respectively. Encouragingly, these cathode Rp values were largely reduced when discharge due to an activation process. The LNF and NiO reversibly formed and decomposed during the oxidation and reduction processes, suggesting that the LNF/NiO hybrid is a potential quasi-symmetrical SOFC electrode material. When using H₂ as fuel and air as oxidant, the maximum power densities of the single cell at 650, 600 and 550 °C were as high as 928, 580 and 329 mW cm^?2, respectively.     

A development of direct hydrazine/hydrogen peroxide fuel cell

A direct hydrazine fuel cell using H₂O₂ as the oxidizer has been developed. The N₂H₄/H₂O₂ fuel cell is assembled by using Ni-Pt/C composite catalyst as the anode catalyst, Au/C as the cathode catalyst, and Nafion membrane as the electrolyte. Both anolyte and catholyte show significant influences on cell voltage and cell performance. The open-circuit voltage of the N₂H₄/H₂O₂ fuel cell reaches up to 1.75 V when using alkaline N₂H₄ solution as the anolyte and acidic H₂O₂ solution as the catholyte. A maximum power density of 1.02 W cm⁻² has been achieved at operation temperature of 80 °C. The number of electrons exchanged in the H₂O₂ reduction reaction on Au/C catalyst is 2.     

Enhancing catalysis activity of La0.6Sr0.4Co0.8Fe0.2O3-δ cathode for solid oxide fuel cell by a facile and efficient impregnation process

The development of high performance electrocatalysts to promote oxygen reduction reaction (ORR) and to prolong the durability of cathodes of solid oxide fuel cell is essential at intermediate or low temperatures. Here, we report a facile and efficient spray impregnation strategy in enhancing catalytic activity of La_0.6Sr_0.4Co_0.8Fe_0.2O_3-δ (LSCF) due to the introduction of a multitude of homogeneous nanoparticles. With a highly active surface abundance in B-site cations, the modified LSCF cathode manifests an area-specific resistance (ASR) of ∼0.140 Ω cm², only a fifth of that for a pristine LSCF cathode (∼0.764 Ω cm²) at 600 °C, and anode-supported fuel cells with the decorated LSCF cathode show markedly improved peak power densities (∼0.94 W cm⁻² at 700 °C). Furthermore, the ORR kinetics of the modified LSCF cathode can be further enhanced by impregnating Ni(NO₃)₂·6H₂O and Co(NO₃)₂·6H₂O solution again. X-ray photoelectron spectroscopy analysis indicates that the homogeneous nanoparticles alter the distribution of Sr_surface and O_surface. It is found that ‘Co’ decoration can effectively alleviate the surface aggregation of Sr and ‘Co’ and ‘Ni’ decoration play a pivotal role in the reactivation of electrode surface.     

Electrochemical performances of LiNiCoMn bifunctional electrode for low temperature solid oxide fuel cells

Lithium transition metal oxides LiNi_0.83Co_0.11Mn_0.06O₂ (NCM-83) and LiNi_0.8Co_0.1Mn_0.1O₂ (NCM-811) are prepared and acted as cathodes and bifunctional electrodes for low temperature solid oxide fuel cells with H₂ and CH₄ fuels. The Ni anode-supported cell with NCM-83 cathode exhibits maximum power density (P_max) of 0.72 W cm⁻² with H₂ fuel at 600 °C. The symmetric cell with NCM-83 electrodes shows high P_max of 0.465 W cm⁻² with H₂ fuel and 0.354 W cm⁻² with CH₄ fuel at 600 °C. And the P_max of the cell with NCM-811 as anode and NCM-83 as cathode is 0.204W cm⁻² with H₂ fuel at 600 °C. The oxygen vacancies in NCM materials are conducive to the rapid oxygen ion conduction of the cathode, and in the anodic reduction atmosphere, the NCM materials will generate Ni/Co active particles in situ, proving the NCM materials can be advanced bifunctional electrode materials for hydrogen oxidation reaction and oxygen reduction reaction at low temperature.     

The comparison of direct borohydride-hydrogen peroxide fuel cell performance with membrane electrode assembly prepared by catalyst coated membrane method and catalyst coated gas diffusion layer method using Ni@Pt/C as anodic catalyst

Carbon supported Ni@Pt nanoparticles are synthesized using sodium dodecyl sulphate (SDS) and sodium borohydride (NaBH₄) as a structure-directing and reducing agents, respectively. The metal loading in synthesized nanocatalyst is 20 wt% and the ratio of Ni:Pt in the nanocatalyst is 1:1. The structural characterizations and morphologies of Ni@Pt/C nanocatalyst are investigated by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD). The electrocatalytic activity of Ni@Pt/C catalyst toward borohydride $\left({\text{BH}}_4^{?}\right)$ oxidation in alkaline medium is studied by means of cyclic voltammetry (CV), chronopotentiometry (CP) and chronoamperometry (CA). The results show that Ni@Pt/C catalyst has superior catalytic activity toward borohydride oxidation (8825.38 mA mg Pt^?1). The Membrane Electrode Assembly (MEA) used in fuel cell set-up is fabricated with catalyst-coated membrane (CCM) and catalyst coated gas diffusion medium (CCG) techniques. The effect of two MEA performances on current–voltage (I–V) and current–power density (I–P) curves in the direct borohydride-hydrogen peroxide fuel cell was investigated using Pt/C 0.5 mg cm^?2 as cathode catalyst and Ni@Pt/C 1 mg cm^?2 as anode catalyst. The influence of cell temperature, sodium borohydride and hydrogen peroxide concentration on the I–V and I–P is determined. The results show that the maximum power density in MEA prepared using CCM method (CCM-MEA) is 68.64 mW cm^?2 at 60 °C, 1 M sodium borohydride and 2 M hydrogen peroxide (H₂O₂) that is higher than MEA prepared using CCG method (CCG-MEA). The impedance results show that with increasing temperature and discharging current, the overall anodic and cathodic charge transfer resistances reduce.     

Pulse electrodeposited cathode catalyst layers for PEM fuel cells

Nanostructured Pt and Pt₃Co cathodes for proton exchange membrane fuel cells (PEMFCs) have been prepared by pulse electrodeposition. For high utilization the catalyst nanoparticles are directly deposited on the microporous layer (MPL) of a commercial available gas diffusion layer (GDL). In order to increase the hydrophilic nature of the substrate surface and thus improve drastically the electrodeposition process and the fuel cell performance, prior to electrodeposition, the carbon substrate is submitted to O₂/Ar plasma activation. Cathodes with different amounts and distributions of Aquivion ionomer within the cathode catalyst layer (CCL) thickness (“homogeneous”, “gradient” and “anti-gradient”), different catalysts (Pt and Pt₃Co) at varied plasma duration and catalyst loading have been prepared. The cathodes are analysed via attenuated total reflection (ATR-IR), goniometer, SEM, 0.5 M H₂SO₄ half-cell and 25 cm² H₂/Air single PEMFC. The highest single fuel cell performance is obtained for 2 min plasma activated Pt₃Co cathode.     

Electrochemical investigations of cobalt-free perovskite cathode material for intermediate temperature solid oxide fuel cell

A novel cobalt-free perovskite zinc-doped lanthanum strontium iron oxide (La_0.8Sr_0.2Zn_xFe_1?xO_3?δ, LSZF, x = 0.1–0.3) is synthesized and evaluated as cathode material for intermediate temperature solid oxide fuel cell (IT-SOFC) with samarium doped ceria (SDC) electrolyte. LSZF cathode at x = 0.2 composition demonstrates the remarkable electrochemical activity at intermediate temperature (550 °C): such as, high electrical conductivity (13.63 S cm^?1), excellent thermal stability with SDC electrolyte (12.10 μK^?1), high surface area (4.52 m² g^?1), extremely reduced area specific resistance (0.69 Ω cm^?2) and low activation energy (0.117 eV). Furthermore, single fuel cells are fabricated using LSZF as a cathode, which exhibits the excellent performance by achieving the high power density of 409 mW cm^?2 under natural gas as a fuel and ambient air as an oxidant at 550 °C with good stability over 10 h. All experimental results indicate that the LSZF is a promising cathode material for natural gas based intermediate temperature fuel cell applications.     

Characterization of Pt supported on commercial fluorinated carbon as cathode catalysts for Polymer Electrolyte Membrane Fuel Cell

Pt nanoparticles supported on carbon monofluoride (CFx), synthesized from H₂PtCl₆ using NaHB₄ as a reducing agent has been investigated as a cathode electrocatalyst in fuel cells. Surface characterization, performed by transmission electron microscopy (TEM) and powder X-ray diffraction (PXRD), shows a homogeneous distribution and high dispersion of metal particles. Kinetic parameters for the electrocatalyst are also obtained from the steady state measurements using a rotating disk electrode (RDE) in 0.5 M H₂SO₄ solution. Analysis by Koutecky–Levich equation indicates an overall 4 e^? oxygen reduction reaction (ORR). Evaluation of the catalyst in single cell membrane electrode assemblies (MEAs) for proton exchange membrane based Direct Methanol Fuel Cell (DMFC) and H₂ Fuel Cell at different temperatures and flows of O₂ and Air are shown and compared against commercial Pt/C as the cathode electrocatalyst. Evaluation of Pt/CFx in H₂ fed fuel cells shows a comparable performance against a commercial catalyst having a higher platinum loading. However, in direct methanol fuel cell cathodes, an improved performance is observed at low O₂ and air flows showing up to 60–70% increase in the peak power density at very low flows (60 mL min^?1).     

A fuel cell with selective electrocatalysts using hydrogen peroxide as both an electron acceptor and a fuel

We have realized a novel hydrogen peroxide fuel cell that uses hydrogen peroxide (H₂O₂) as both an electron acceptor (oxidant) and a fuel. H₂O₂ is oxidized at the anode and reduced at the cathode. Power generation is based on the difference in catalysis toward H₂O₂ between the anode and cathode. The anode catalyst oxidizes H₂O₂ at a more negative potential than that at which the cathode catalyst reduces H₂O₂. We found that Ag is suitable for use as a cathode catalyst, and that Au, Pt, Pd, and Ni are desirable for use as anode catalysts. Alkaline electrolyte is necessary for power generation. The performance of this cell is clearly explained by cyclic voltammograms of H₂O₂ at these electrodes. This cell does not require a membrane to separate the anode and cathode compartments. Furthermore, separate paths are not needed for the fuel and electron acceptor (oxidant). These properties make it possible to construct fuel cells with a one-compartment structure.     

High-performance SOFC based on a novel semiconductor-ionic SrFeO3-δ–Ce0.8Sm0.2O2-δ membrane

The semiconductor-ionic composite membrane has been recently developed for a novel solid oxide fuel cell (SOFC), i.e., the semiconductor-ion membrane fuel cell (SIMFC). In this work, the perovskite-type SrFeO_3-δ (SFO) as semiconductor material was composited with ionic conductor Ce_0.8Sm_0.2O_2-δ (SDC) to form the SFO-SDC composite membrane for SIMFCs. The SFO-SDC SIMFCs using the optimized weight ratio of 3:7 SFO-SDC membrane obtained the best performances, 780 mW cm^?2 at 550 °C, compared to 348 mW cm^?2 obtained from the pure SDC electrolyte fuel cell. Introduction of SFO into SDC can extend the triple phase boundary and provide more active sites for accelerating the fuel cell reactions, thus significantly enhanced the cell power output. Moreover, SFO was employed as the cathode, and a higher power output, 907 mW cm^?2 was achieved, suggesting that SFO cathode is more compatible for the SFO-SDC system in SIMFCs. This work provides an attractive strategy for the development of low temperature SOFCs.     

La1−xSrxFe0.7Ni0.3O3−δ as both cathode and anode materials for Solid Oxide Fuel Cells

La_1?xSr_xFe_0.7Ni_0.3O_3?δ (x = 0, 0.1 and 0.2, LSFNx) are investigated as both cathode and anode materials for Solid Oxide Fuel Cells (SOFCs). The structure, microstructure and electrochemical properties of these materials are studied under oxidizing and reducing atmospheres. In air, the electrodes exhibit polarization resistance of 0.1 Ωcm² at 800 °C under open circuit voltage. In a H₂ atmosphere, Ni nanoparticles are exsolved on the surface, leading to a polarization resistance as low as 0.06 Ωcm². A cell with a 350 μm thick La_0.9Sr_0.1Ga_0.8Mg_0.2O_3?δ electrolyte and LSFN electrodes generates a power output of 540 mWcm^?2 at 800 °C. Moreover, stable values of power density are obtained after successive oxidation/reduction cycles, confirming the reversibility of the electrodes.     

High performance of protonic solid oxide fuel cell with BaCo0.7Fe0.22Sc0.08O3−δ electrode

Solid oxide fuel cells (SOFCs) have attracted tremendous attention for their combination of environmental power generation and fuel flexibility. Proton conducting SOFCs (P-SOFCs) demonstrate advantages over oxygen-ion conducting SOFCs, such as less activation energies on ionic transport and higher fuel utilization efficiency. Central to the devices is a suitable cathode with high catalytic activity. Herein, a cubic perovskite BaCo_0.7Fe_0.22Sc_0.08O_3?δ (BCFSc) has been applied as the cathode in proton-conducting solid state fuel cell (SOFC) with BaZr_0.1Ce_0.7Y_0.2O_3?δ (BZCY) electrolyte. Peak power densities of 760, 591, 452 and 318 mW cm^?2 are obtained at 650, 600, 550 and 500 °C with humidified hydrogen as the fuel and air as the oxidant. A low polarization resistance of 0.05 Ω cm² under open circuit at 650 °C is observed.     

Copper hexacyanoferrate as cathode material for hydrogen peroxide fuel cell

The current need for handheld electronic devices with high energy autonomy has amplified research into clean and mobile energy source developments. Among suitable and promising technologies for this application, fuel cells, FCs are highlighted because of their minimal emission of pollutants and high efficiency. One type of FCs that has yet to be studied is the hydrogen peroxide/direct hydrogen peroxide fuel cell (DPPFCs). The present work is dedicated to the development of DPPFCs of one compartment using copper hexacyanoferrates (CuHCFs) as cathodic material and a Ni grid as anodic material. CuHCFs containing Fe^II and/or Fe^III were synthesized, characterized and their electrocatalyst performances were compared in 0.1 mol L⁻¹ HCl and 0.5 mol L⁻¹ H₂O₂. The maximum power densities reached for the CuFe^II was 8.3 mW cm⁻² and for the CuFe^IIFe^III was 2.9 mW cm⁻². The CuHCFs cathode materials show promising results, standing out as innovative materials for such an application.     

Electrooxidation of hydrogen peroxide and sodium borohydride on Ni deposited carbon fiber electrode for alkaline fuel cells

In this study, Ni deposited carbon fiber electrode (Ni/CF) prepared by electroless deposition method was examined for their redox process and electrocatalytic activities during the oxidation of hydrogen peroxide and sodium borohydride in alkaline solutions. The Ni/CF catalyst was characterized by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDAX), scanning electron microscopy (SEM) and electrochemical voltammetry analysis. The electrocatalytic activity of the Ni/CF for oxidation of hydrogen peroxide and sodium borohydride in alkaline solutions was investigated by cyclic voltammetry. The anodic peak current density is found to be three times higher on Ni/CF catalyst for sodium borohydride compared to that for hydrogen peroxide. Preliminary tests on a single cell of a direct borohydride/peroxide fuel cell (DBPFC) and direct peroxide/peroxide fuel cell (DPPFC) indicate that DBPFC with the power density of 5.9 mW cm⁻² provides higher performance than DPPFC (3.8 mWcm⁻²).     

A woven thread-based microfluidic fuel cell with graphite rod electrodes

A woven thread-based microfluidic fuel cell based on graphite rod electrodes is proposed. Both inter-fiber gaps and inter-weave spaces could provide flow channels for the liquid transport through the woven cotton thread. Therefore, no external pumps are required to maintain the co-laminar flow, benefiting for the integration and miniaturization. In the experiment, sodium formate and hydrogen peroxide are used as fuel and oxidant, respectively. To improve the electrochemical reaction kinetics, KOH and H₂SO₄ serve as supporting electrolyte at the anode and cathode, respectively. Na₂SO₄ solution is used as the electrolyte to separate the cathode and anode in the middle flow channel and alleviate the reactant crossover. The open circuit potential of the fuel cell achieves 1.44 V and the maximum current density and power density are 56.6 mA cm^?2 and 20.7 mW cm^?2, respectively. Moreover, the cell performance reduces with increasing the electrode distance due to a high ohmic resistance. With an increase in the fuel concentration from 1 M to 4 M, the performance increases and it reduces with further increasing to 6 M owing to a correspondingly low flow rate. The highest fuel utilization rate reaches 10.9% at 4 M fuel concentration.     

Ni and N co-doped MoCx as efficient electrocatalysts for hydrogen evolution reaction at all-pH values

To achieve sustainable production of H₂ fuel through water splitting, noble-metal-free catalysts have been extensively studied for hydrogen evolution reaction (HER), especially molybdenum-based catalysts. Herein, we report the Ni, N-codoped MoC_x (Ni–N–MoC_x) nanoparticles synthesized from NiMoO₄ precursor by oily-solvent-assisted strategy, following the calcination with dicyandiamide. As-obtained Ni–N–MoC_x in different magnified SEM images shows grainy structure, MoC_x nanoparticles uniformly disperse in carbon substrate. The obtained electrocatalysts can also efficiently electrocatalytic HER in a wide pH value. Ni–N–MoC_x shows an onset potential of ?74 mV, an overpotential of 163 mV to reach a current density of 10 mA/cm² in acid media, an onset potential of ?37 mV and overpotential of 124 mV to reach 10 mA/cm² in alkaline media. The present study provides some guidelines for preparing the uniformly doped electrocatalysts from multiple compounds with devolatilization characteristics.     

Reversible H2/H2O electrochemical conversion mechanisms on the patterned nickel electrodes

The patterned nickel (Ni) electrode enables to quantify the triple-phase boundary (TPB) length and Ni surface area as well as exclude the interference of bulk gas diffusion. In this study, the patterned Ni electrodes are investigated in both the solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) modes at the atmosphere of H₂O/H₂. The experimental test shows the patterned Ni electrode keeps stable and intact only at the specific operating condition due to instability of Ni at the H₂O-containing atmosphere. The effects of the temperature, partial pressure of H₂O and H₂ on the electrochemical performance are measured. The electrochemical performance has a positive correlation with the temperature, partial pressure of H₂ and H₂O. Further, the experimental results are compared with the mechanism containing two-step charge-transfer reaction used in the existing literature. An analytical calculation is performed to indicate the rate-limiting steps may be different for SOFC and SOEC modes. In SOFC mode, H₂ electrochemical oxidation could be dominated by both charge transfer reaction at low polarization voltage and by the charge-transfer reaction H(Ni) + O^2?(YSZ) → OH^?(YSZ) + (Ni) + e^? at high polarization voltage, however in SOEC mode, H₂O electrochemical reduction is considered to be dominated by H₂O(YSZ) + (Ni) + e^? → OH^?(YSZ) + H(Ni).     

Electrochemical properties and durability of in-situ composite cathodes with SmBa0.5Sr0.5Co2O5+δ for metal supported solid oxide fuel cells

The electrochemical properties and long-term performance of an in-situ composite cathode comprised of SmBa_0.5Sr_0.5Co₂O_5+δ (SBSCO) and Ce_0.9Gd_0.1O_2?δ (CGO91) are investigated for metal supported solid oxide fuel cell (MS-SOFC) application.The Area Specific Resistance (ASR) of an in-situ composite cathode comprised of 50 wt% of SBSCO and 50 wt% of CGO91 (SBSCO:50) is 0.031 Ω cm² in the first stage of measurement at 700 °C; this value of ASR increases to 0.138 Ω cm² after 1000 h. The ASR of SBSCO:50 (in-situ sample at 750 °C) is 0.014 Ω cm² at the initial stage of measurement; the increase of ASR after 1000 h at 750 °C is only 0.067 Ω cm². These results suggest that the optimum temperature for in-situ firing of an SBSCO:50 cathode sample of MS-SOFC is higher than 700 °C, ideally around 750 °C.