Fabrication and performance evaluation of electrolyte-combined α-LiAlO2 matrices for molten carbonate fuel cells

To improve the unit cell performance and stability, molten carbonate fuel cell (MCFC) matrices were fabricated using synthetic α-LiAlO₂ powder and they showed mechanical and microstructural stability under thermal cycle tests. The pure α-LiAlO₂ matrix demonstrated stability with high open-circuit voltage (OCV) and maximum power density during many thermal cycle tests (more than 15 repetitions). Furthermore, to minimize the change in stack height during stack start-up and to improve mechanical and microstructural stabilities of the matrix, the electrolyte-combined α-LiAlO₂ matrix was optimized by controlling the mixing ratio of synthetic α-LiAlO₂ and Li/K carbonate powders. The suitable electrolyte content was fixed at approximately 50 vol.% for the homogeneously filled pores of the pure α-LiAlO₂ matrix. These matrices showed good microstructural stability during five thermal cycle tests in an air atmosphere at 923 K and with improved unit cell performance (0.127 W cm⁻²) under MCFC operating conditions.In unit cell and thermal cycling tests, the optimized matrices were stable through more than 20 repetitions.     

Characteristics of aluminum-reinforced γ-LiAlO2 matrices for molten carbonate fuel cells

A key component in molten carbonate fuel cells (MCFCs) is the electrolyte matrix, which provides both ionic conduction and gas sealing. During initial MCFC stack start-up and operation (650 °C), the matrix experiences both mechanical and thermal stresses as a result of the difference in thermal expansion coefficients between the LiAlO₂ ceramic particles and the carbonate electrolyte that causes cracking of the matrix. A pure γ-LiAlO₂ matrix, however, has poor mechanical strength and low thermal expansion coefficients. In this study, fine γ-LiAlO₂ powders and pure Al (3/20/50 μm)/Li₂CO₃ particles are used as a matrix and as reinforcing materials, respectively. The Al phase transforms completely into γ-LiAlO₂ at 650 °C within 10 h. The mechanical strength of these matrices (283.48 gf mm⁻²) increases nearly threefold relative to that of a pure γ-LiAlO₂ matrix (104.01 gf mm⁻²). The mismatch of the thermal expansion coefficient between the matrix and electrolyte phases can be controlled by adding Al particles, which results in improved thermal stability in the initial heating-up step. In unit-cell and thermal-cycling tests, the optimized matrix demonstrates superior performance over pure γ-LiAlO₂ matrices.     

Dual ionic conductive membrane for molten carbonate fuel cell

Within this study, the electrochemically inert, molten carbonate fuel cell (MCFC) $\text{γ}$-LiAlO₂ matrix is replaced by oxygen ion conducting ceramics, typical for solid oxide fuel cell (SOFC) application. Such solution leads to synergistic ion transport both by molten carbonate mix (CO₃^2-) and yttria-stabilized zirconia (YSZ) or samaria-doped ceria (SDC) matrix (O^2-).Single unit cell tests confirm that application of hybrid ionic membrane increases the performance (power density) of the MCFC over pure $\text{γ}$-LiAlO₂ for a wide range of operating temperatures (600 °C–750 °C). Cell power density with SDC and YSZ matrices is 2% and 13% higher, respectively, compared to the $\text{γ}$-LiAlO₂ at typical 650 °C operating temperature of MCFC.     

Using aluminum and Li2CO3 particles to reinforce the α-LiAlO2 matrix for molten carbonate fuel cells

The electrolyte substrate (matrix) of a molten carbonate fuel cell (MCFC) provides both ionic conduction and gas sealing. During the starting-up and operating of MCFC stacks at 923 K, the matrix can experience mechanical stresses that can cause cracking. In particular, the pure α-LiAlO₂ that is generally used for the MCFC possesses poor mechanical strength. In this study, we employed Al and Li₂CO₃ particles as reinforcement materials to increase the mechanical strength of the α-LiAlO₂ matrix for its stable long-term operation. The mechanical strength of the matrix increased dramatically after adding Al particles into the pure matrix. Moreover, we operated a single cell for 2000 h after adding Li₂CO₃ particles into the Al-reinforced matrix to prevent a Li-ion shortage caused by a lithiated Al reaction in the matrix.     

Electrical conductivity measurements of aqueous and immobilized potassium hydroxide

It is important to know the conductivity of the electrolyte of an alkaline electrolysis cell at a given temperature and concentration so as to reduce the ohmic loss during electrolysis through optimal cell and system design. The conductivity of aqueous KOH at elevated temperatures and high concentrations was investigated using the van der Pauw method in combination with electrochemical impedance spectroscopy (EIS). Conductivity values as high as 2.7 S cm⁻¹ for 35 wt%, 2.9 S cm⁻¹ for 45 wt%, and 2.8 S cm⁻¹ for 55 wt% concentrated aqueous solutions were measured at 200 °C. Micro- and nano-porous solid pellets were produced and used to immobilize aqueous KOH solutions. These are intended to operate as ion-conductive diaphragms (electrolytes) in alkaline electrolysis cells, offering high conductivity and corrosion resistance. The conductivity of immobilized KOH has been determined by the same method in the same temperature and concentration range. Conductivity values as high as 0.67 S cm⁻¹ for 35 wt%, 0.84 S cm⁻¹ for 45 wt%, and 0.73 S cm⁻¹ for 55 wt% concentrated immobilized aqueous solutions were determined at 200 °C. Furthermore, phase transition lines between the aqueous and aqueous + gaseous phase fields of the KOH/H₂O system were calculated as a function of temperature, concentration and pressure in the temperature range of 100–350 °C, for concentrations of 0–60 wt% and at pressures between 1 and 100 bar.     

Nano Ni layered anode for enhanced MCFC performance at reduced operating temperature

Nanoparticles of Ni and Ni–Al₂O₃ were coated on a molten carbonate fuel cell (MCFC) anode by spray method to enlarge the electrochemical reaction sites at triple phase boundaries (TPBs). Both nano Ni coated anode and nano Ni–Al₂O₃ anode exhibited significant reduction of anode polarization, thanks to smaller charge transfer resistance. The maximum power density of nano Ni coated anode was 159 mW cm⁻² at current density of 300 mA cm⁻² operating at 600 °C. This is about 7% increase from the standard cell performance tested and compared in the study. Although low performance of nano coated Ni–Al₂O₃ cell is observed due to electrolyte consumption, the stability of cell performance during operation time is more favorable in MCFCs operation.     

Ceria interlayer-free Ba0.5Sr0.5Co0.8Fe0.2O3−δ–Sc0.1Zr0.9O1.95 composite cathode on zirconia based electrolyte for intermediate temperature solid oxide fuel cells

We synthesized Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCF) powders with a primary particle size of 20 nm using a Pechini type method. By using nanocrystalline BSCF powders, we were able to fabricate a ceria interlayer-free nanoporous cathode on a scandia stabilized zirconia (ScSZ) electrolyte at low temperatures. Cathodes sintered below 750 °C lacked sufficient mechanical adhesion to the electrolyte, while electrode was well adhered to the electrolyte when fired at 800 °C. The symmetrical BSCF-ScSZ|yttria stabilized zirconia (YSZ)|BSCF-ScSZ half-cell that we generated had an exceptionally low polarization resistance of 0.06 Ω·cm² at 700 °C. The maximum power density of the BSCF-ScSZ|ScSZ|Ni-ScSZ unit cell was over 1 W cm⁻² at 700 °C. We investigated the durability of the BSCF-ScSZ composite cathode by 30 thermo-cycles performed by varying the temperature from 200 to 700 °C. The polarization resistance after the test remained low at less than 0.08 Ω·cm².     

Mechanical strength improvement of aluminum foam-reinforced matrix for molten carbonate fuel cells

During the cell operation of molten carbonate fuel cells (MCFCs), matrix cracks caused by poor mechanical strength accelerate cell performance degradation. Therefore, for a stable long-term cell operation, the improvement of mechanical properties of matrix is highly required. In this study, aluminum foam was used to enhance the mechanical strength of the matrix as a 3D (three dimensional) support structure. Unlikely conventional matrix (pure α-LiAlO₂ matrix) which has paste-like structure at the MCFC operating temperature, Al foam-reinforced α-LiAlO₂ matrix has significantly strong mechanical strength because the 3D network structure of Al foam can form the harden alumina skin layer during a cell operation. As a result, the mechanical strength of the Al foam-reinforced α-LiAlO₂ matrix was enhanced by 9 times higher than the pure α-LiAlO₂ matrix in a 3-point bending test. In addition, thermal cycle test showed notable cell stability due to strong mechanical strength of Al foam-reinforced α-LiAlO₂ matrix. The Al foam-reinforced α-LiAlO₂ matrix shows appropriate microstructure to preserve the liquid electrolyte when performing the mercury porosimeter analysis and differential pressure test between anode and cathode. Moreover, evaluation of stability and durability for a long-term cell operation were demonstrated by single cell test for 1,000 h.     

Preparation and electrochemical properties of strontium doped Pr2NiO4 cathode materials for intermediate-temperature solid oxide fuel cells

Pr_2−xSr_xNiO₄ (PSNO, x = 0.3, 0.5 and 0.8) cathode materials for intermediate-temperature solid oxide fuel cell (IT-SOFC) were synthesized by a glycine-nitrate process using Pr₆O₁₁, Ni(NO₃)₂·6H₂O and SrCO₃ powders as raw materials. Phase structure of the synthesized powders was characterized by X-ray diffraction analysis (XRD). Microstructure of the sintered PSNO samples was observed and thermal expansion coefficient (TEC) and electrical conductivity were investigated. Electrochemical impedance spectroscopy (EIS) measurement of the PSNO materials on Sm_0.2Ce_0.8O_1.9 (SCO) electrolyte was carried out, and single cells based on the PSNO cathodes were also assembled and their performances were tested. The results show that the synthesized PSNO powders have pure K₂NiF₄-type structure and the PSNO materials are chemically stable with Sm_0.2Ce_0.8O_1.9 (SCO) electrolyte. The sintered PSNO samples have porous and fine microstructure with pore size smaller than 1 μm. Average thermal expansion coefficient of the PSNO materials is about 12–13 × 10⁻⁶ K⁻¹ at 200–800 °C and the electrical conductivity is in the range of 70–120 Scm⁻¹ at 800 °C. Area specific resistance (ASR) of the Pr_2−xSr_xNiO₄ materials on SCO electrolyte is 0.407 Ωcm², 0.126 Ωcm² and 0.112 Ωcm² for x = 0.3, 0.5 and 0.8 at 800 °C, respectively. Maximum open circuit voltage (OCV) and power density of the single NiO-SCO/SCO/PSNO cells are 0.75 V and 298 mWcm⁻² at 700 °C, respectively, which indicates that Pr_2−xSr_xNiO₄ may be a potential cathode material for IT-SOFC.     

Tantalum nitride coated AISI 316L as bipolar plate for polymer electrolyte membrane fuel cell

Tantalum nitride (TaN) thin films are deposited on AISI 316L stainless steel by inductively coupled, plasma-assisted, reactive magnetron sputtering at various N₂ flow rates. TaN film behavior is investigated in simulated polymer electrolyte membrane fuel cell (PEMFC) conditions by using electrochemical measurement techniques for application as bipolar plates. The results of a potentio-dynamic polarization test under PEMFC cathodic and anodic conditions indicate that the corrosion current density of the TaN_x films is of the order of 10⁻⁷ A cm⁻² (at 0.6 V) and 10⁻⁸ A cm⁻² (at −0.1 V), respectively; these results are considerably better than the individual results for metallic Ta films and AISI 316L stainless steel. The TaN_x films exhibit superior stability in a potentio-static polarization test performed under PEMFC cathodic and anodic conditions. The interfacial contact resistance of the films is measured in the range of 50-150 N cm⁻², and the lowest value is 11 mΩ cm² at a compaction pressure of 150 N cm⁻².     

Performance and degradation of La0.8Sr0.2Ga0.85Mg0.15O3−δ electrolyte-supported cells in single-chamber configuration

Electrolyte-supported cells were made of a La_0.8Sr_0.2Ga_0.85Mg_0.15O_3−δ (LSGM2015) electrolyte (200 μm thickness) prepared by ethylene glycol complex solution synthesis, isostatic pressing and sintered at 1400 °C, a Ni-SDC anode, a Sm_0.2Ce_0.8O_3−δ (SDC) buffer-layer between anode and electrolyte, and a La_0.5Sr_0.5CoO_3−δ-SDC cathode. The cells were tested in single-chamber configuration using methane–air mixtures. The results of X-ray diffraction and SEM-EDS showed a single-phase in the electrolyte and conductivities (∼0.01 S cm⁻¹ at 650 °C) close to the typical values. Good cell power densities of 215 and 102 mW cm⁻² were achieved under CH₄/O₂ = 1.4 of at 800 and 650 °C, respectively. However, the cell stability tests indicated that the operating temperature strongly influenced on the cell performance after 100 h. While no significant change in the power density was observed working at 650 °C, a clear performance degradation was evidenced at 800 °C. SEM-EDS revealed an appreciable degradation of the electrolyte and both the electrodes.     

Effect of metal particle size and Nafion content on performance of MEA using Ir-V/C as anode catalyst

Ir and Ir-V nanoparticles were synthesized in ethylene glycol using IrCl₃ and NH₄VO₃ as the Ir and V precursors, respectively. These nanoparticles were evaluated as anode catalysts in proton exchange membrane fuel cells (PEMFCs). A thermal treatment of the catalysts at 200 °C in a reducing atmosphere leads to very high electrocatalytic activity for the hydrogen oxidation reaction. The fuel cell performance reveals an optimal Nafion ionomer content of 25% in the catalyst layer used for the MEA fabrication. The electrocatalytic effects related to the change in the electrocatalyst structure are discussed based on the data obtained by X-ray diffraction (XRD) and transmission electron microscopy (TEM). In addition, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques are used in-situ to assess the kinetics of hydrogen oxidation on the surface of these catalysts. A maximum power density of 1016.6 mW cm⁻² was obtained at 0.598 V and 70 °C with an anode catalyst loading of 0.4 mg (Ir) cm⁻². This performance is 50.7% higher than that for commercially available Pt/C catalysts under the same conditions. In addition, we also tested the anode catalyst with a low loading of 0.1 mg (Ir) cm⁻², the maximum power density is 33.8% higher than that of the commercial Pt/C catalyst with a loading of 0.4 mg (Pt) cm⁻².     

Ba0.9Co0.5Fe0.4Nb0.1O3−δ as novel oxygen electrode for solid oxide electrolysis cells

A novel perovskite oxide Ba_0.9Co_0.5Fe_0.4Nb_0.1O_3−δ (BCFN) was prepared and characterized as oxygen electrode for solid oxide electrolysis cells (SOECs) using La_0.8Sr_0.2Ga_0.83Mg_0.17O_3−δ (LSGM) as electrolyte. Symmetrical half-cell study shows that the polarization resistance of BCFN is only 0.08 Ω cm² at 750 °C in air. Electrochemical impedance spectra and voltage-current curves of the electrolysis cell with the configuration of BCFN|LSGM|La_0.4Ce_0.6O_2−x|Ni-Ce_0.9Gd_0.1O_1.95 were measured as a function of operating temperature and steam concentrations to characterize the electrolysis cell performances. Under an applied electrolysis voltage of 1.5 V, the maximum consumed current density increased from 0.835 A cm⁻² at 700 °C to 3.237 A cm⁻² at 850 °C with 40 vol.% absolute humidity (AH), and the hydrogen generation rate of the cell can be up to 1352 mL cm⁻² h⁻¹ with 40 vol.% AH at 850 °C. Further, the electrolysis cell has showed very stable performance during a 200 h short-term electrolysis testing, indicating that BCFN can be a very promising candidate for the oxygen electrode of SOECs using LSGM electrolyte.     

Microwave-assisted low temperature fabrication of nanostructured α-Fe2O3 electrodes for solar-driven hydrogen generation

It is demonstrated for the first time that significant enhancement of photoelectrochemical performance could be achieved by using microwave-assisted annealing for the fabrication of α-Fe₂O₃ thin films. The process can also lead to significant energy savings (>60% when compared with conventional methods). Different types of Fe thin films were oxidized using both microwave and conventional heating techniques. The photoelectrochemical performance of electrodeposited, undoped and Si-doped iron oxide samples showed that microwave-annealing resulted in superior structural and performance enhancements. The photocurrent densities obtained from microwave annealed samples are among the highest values reported for α-Fe₂O₃ photoelectrodes fabricated at low temperatures and short times; the highest photocurrent density at 0.55 V vs. V_Ag/AgCl, before the dark current onset, was 450 μA cm⁻² for the Si-doped films annealed at 270 °C for 15 min using microwave irradiation (and 180 μA cm⁻² at 0.23 V vs. V_Ag/AgCl) while conventional annealing at the same temperature resulted in samples with negligible (3 μA cm⁻²) photoactivity. In contrast, a 450 °C/15 min conventional heat treatment only resulted in a film with 25% lower photocurrent density than that of the microwave annealed sample. The improved performance is attributed to the lower processing temperatures and rapidity of the microwave method that help to retain the nanostructure of the thin films whilst restricting the grain growth to a minimum. The lower processing temperature requirements of the microwave process can also open up the possibility of fabricating hematite thin films on conducting, flexible, plastic electronic substrates.     

Electrochemical behavior of Ba0.5Sr0.5Co0.2−xZnxFe0.8O3−δ (x = 0-0.2) perovskite oxides for the cathode of solid oxide fuel cells

Zinc-doped barium strontium cobalt ferrite (Ba_0.5Sr_0.5Co_0.2−xZn_xFe_0.8O_3−δ (BSCZF), x = 0, 0.05, 0.1, 0.15, 0.2) powders with various proportions of zinc were prepared using the ethylenediamine tetraacetic acid (EDTA)-citrate method with repeated ball-milling and calcining. They were then evaluated as cathode materials for solid oxide fuel cells at intermediate temperatures (IT-SOFCs) using XRD, H₂-TPR, SEM, and electrochemical tests. By varying the zinc doping (x) from zero to 0.2 (as a substitution for cobalt which ranged from zero to 100%), it was found that the lowest doping of 0.05 (BSCZF05) resulted in the highest electrical conductivity of 30.7 S cm⁻¹ at 500 °C. The polarization resistances of BSCZF05 sintered at 950 °C were 0.15 Ω cm², 0.28 Ω cm² and 0.59 Ω cm² at 700 °C, 650 °C and 600 °C, respectively. The resistance decreased further by about 30% when Sm_0.2Ce_0.8O_2−δ (SDC) electrolyte particles were incorporated and the sintering temperature was increased to 1000 °C. Compared to BSCF without zinc, BSCZF experienced the lowest decrease in electrochemical properties when the sintering temperature was increased from 950 °C to 1000 °C. This decrease was due to an increase in thermal stability and a minimization in the loss of some cobalt cations without a decrease in the electrical conductivity. Using a composite cathode of BSCZF05 and 30 wt.% of SDC, button cells composed of an Ni-SDC support with a 30 μm dense SDC membrane exhibited a maximum power density of 605 mW cm⁻² at 700 °C.     

In situ sinterable cathode with nanocrystalline La0.6Sr0.4Co0.2Fe0.8O3−δ for solid oxide fuel cells

A nanocrystalline powder with a lanthanum based iron- and cobalt-containing perovskite, La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF), is investigated for solid oxide fuel cell (SOFC) applications at a relatively low operating temperature (600-800 °C). A LSCF powder with a high surface area of 88 m² g⁻¹, which is synthesized via a complex method with using inorganic nano dispersants, is printed onto an anode supported cell as a cathode electrode. A LSCF cathode without a sintering process (in situ sintered cathode) is characterized and compared with that of a sintering process at 780 °C (ex situ sintered cathode). The in situ sintered SOFC shows 0.51 A cm⁻² at 0.9 V and 730 °C, which is comparable with that of the ex situ sintered SOFC. The conventional process for SOFCs, the ex situ sintered SOFC, including a heat treatment process after printing the cathodes, is time consuming and costly. The in situ sinterable nanocrystalline LSCF cathode may be effective for making the process simple and cost effective.     

High activity of Au-Cu/C electrocatalyst as anodic catalyst for direct borohydride-hydrogen peroxide fuel cell

Carbon supported Au-Cu bimetallic nanoparticles are prepared by a modified NaBH₄ reduction method in aqueous solution at room temperature. The electrocatalytic activities of the Au-Cu/C catalysts are investigated by cyclic voltammetry, chronoamperometry, chronopotentiometry and fuel cell experiments. It has been found that the Au-Cu/C catalysts have much higher catalytic activity for the direct oxidation of BH₄⁻ than Au/C catalyst. Especially, the Au₆₇Cu₃₃/C catalyst presents the highest catalytic activity for BH₄⁻ electrooxidation among all as-prepared catalysts, and the DBHFC using Au₆₇Cu₃₃/C anode catalyst and Au/C cathode catalyst shows the maximum power density of 51.8 mW cm⁻² at 69.5 mA cm⁻² and 20 °C.     

Effects of a current treatment for an in-situ sintered cathode in a Ni-supported solid oxide fuel cell

Metal-supported solid oxide fuel cells (SOFCs) are one of the most promising candidates for applications in power plants as well as in portable applications due to their good mechanical and thermal properties. A Ni-supported SOFC that consists of a metal support (Ni, ∼180 μm), an anode functional layer (Ni-yttrium stabilized zirconia YSZ, ∼15 μm), an electrolyte (YSZ, ∼5 μm), and a nanocrystalline La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF) cathode is prepared. A nanocrystalline LSCF synthesized with ethylenediaminetetraacetic acid, citric acid, and inorganic nanodispersants, is used as an in situ sinterable cathode. The Ni-supported SOFC with nanocrystalline LSCFs is operated without a high temperature treatment for cathode sintering. The cell exhibits the maximum power density of 580 mW cm⁻² at 780 °C. A current treatment for 8 h (0.5 A cm⁻² at 780 °C) enhances the interfacial contact between the cathode and the electrolyte. After the current treatment, the maximum power density at 730 °C increase by 1.6 times from 260 mW cm⁻² to 390 mW cm⁻². The ohmic resistance (R_ohm) at 730 °C decreases from 0.43 Ω cm² to 0.21 Ω cm² and the charge transfer polarization at 0.7 V decreases from 0.42 Ω cm² to 0.30 Ω cm² due to lowered interfacial resistance between the cathode and the electrolyte. However, the mass transfer polarization increases from 0.09 Ω cm² to 0.17 Ω cm², which may result from the morphological change in the porous microstructure of the Ni support. The current treatment of the Ni-supported SOFC with in situ sintered LSCFs exhibit an increment in fuel cell performance due to the lowered ohmic resistance, which is beneficial for simple and mechanically improved fabrication and operation of metal-supported SOFCs.     

La0.6Sr0.4Fe0.8Cu0.2O3−δ perovskite oxide as cathode for IT-SOFC

A La_0.6Sr_0.4Fe_0.8Cu_0.2O_3−δ (LSFCu) perovskite was investigated as a cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFC). The LSFCu material exhibited chemical compatibility with the Sm_0.2Ce_0.8O_1.9 (SDC) electrolyte up to a temperature of 1100 °C. The electrical conductivity of the sintered sample was measured as a function of temperature from 100 to 800 °C. The highest conductivity of about 238 S cm⁻¹ was observed for LSFCu. The average thermal-expansion coefficient (TEC) of LSFCu was 14.6 × 10⁻⁶ K⁻¹, close to that of typical CeO₂ electrolyte material. The investigation of electrical properties indicated that the LSFCu cathode had lower interfacial polarization resistance of 0.070 Ω cm² at 800 °C and 0.138 Ω cm² at 750 °C in air. An electrolyte-supported single cell with 300 μm thick SDC electrolyte and LSFCu as cathode shows peak power densities of 530 mW cm⁻² at 800 °C.     

Carbon supported Pt hollow nanospheres as anode catalysts for direct borohydride-hydrogen peroxide fuel cells

The carbon supported Pt hollow nanospheres were prepared by employing cobalt nanoparticles as sacrificial templates at room temperature in aqueous solution and used as the anode electrocatalyst for direct borohydride-hydrogen peroxide fuel cell (DBHFC). The physical and electrochemical properties of the as-prepared electrocatalysts were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP) and fuel cell test. The results showed that the carbon supported Pt nanospheres were coreless and composed of discrete Pt nanoparticles with the crystallite size of about 2.8 nm. Besides, it has been found that the carbon supported Pt hollow nanospheres exhibited an enhanced electrocatalytic performance for BH₄⁻ oxidation compared with the carbon supported solid Pt nanoparticles, and the DBHFC using the carbon supported Pt hollow nanospheres as electrocatalyst showed as high as 54.53 mW cm⁻² power density at a discharge current density of 44.9 mA cm⁻².