Barium cobaltite nanoparticles: Sol-gel synthesis and characterization and their electrochemical hydrogen storage properties

The study of the effect of different chelating agents in the Pechini method on the morphology has been a promising strategy that can be used for practical tuning of the nanoparticle's morphology and hence the electrochemical hydrogen storage capacity. In the current study, the conventional Pechini sol-gel approach was used to prepare the Ba₂Co₉O₁₄ nanoparticles as a novel hydrogen storage material. The X-ray diffraction investigation approved the formation of Ba₂Co₉O₁₄ with a Hexagonal crystal structure for all of the synthesized samples. The scanning electron microscopy (SEM) revealed when citric acid was used as a chelating agent, nanoparticles with finer and more uniform morphology were obtained rather than other chelating sources. The transmission electron microscopy (TEM) showed in the presence of citric acid; the size of the synthesized nanoparticles was between 14 and 24 nm. According to the Diffuse Reflectance Spectroscopy (DRS) analysis, the calculated bandgap of synthesized nanoparticles was approximately 3.2 eV, which indicates that synthesized nanoparticles were semiconductors in essence. The electrochemical hydrogen adsorption/desorption results showed that the sample synthesized by the citric acid has an enhancement in electrochemical hydrogen storage of approximately 800 mAh/g after 15 cycles.     

Green sol-gel auto-combustion synthesis,characterization and investigation of the electrochemical hydrogen storage properties of barium cobalt oxide nanocomposites with maltose

Barium cobalt oxide nanocomposites (Ba₂Co₉O₁₄/Co₃O₄ NCs) as potential hydrogen storage material fabricated by sol-gel auto-combustion method using maltose as reductant, for the first time. Three different ratios of Ba:maltose were applied, including 1:5.5, 1:11 and 1:22 for morphological engineering. X-Ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FT-IR), along with Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission electron microscopy (TEM) images was applied for study the composition and structure of as-prepared samples. Also, the magnetic, optical and electrochemical properties of optimum sample were inquired using VSM, DRS and CV techniques. The porosity and surface properties of NCs were checked by Brunauer-Emmett-Teller (BET) measurements. FE-SEM micrographs of all maltose assisted-synthesis products showed formation of hexagonal nanoparticles on the surfaces of the microplates. According to FE-SEM, HRTEM and XRD results, 1:22 ratio of Ba:maltose and calcination process of 900 °C for 4 h, was selected as optimum condition. The electrochemical hydrogen sorption capability of obtained Ba₂Co₉O₁₄/Co₃O₄ NCs was studied according to chronopotentiometry charge-discharge procedures in KOH medium and performed 1100 mAh/g discharge capacity. Based on the obtained results, Ba₂Co₉O₁₄/Co₃O₄ NCs can be promising compounds to improve the electrochemical performance of hydrogen storage.     

Enhanced electrochemical hydrogen storage performance of titanate-based nanostructures synthesized by facile auto-combustion: Li2TiO3 nanostructures versus LaTiO3 nanoperovskites

Green energies are vital for near-future energy needs. Hydrogen is a promising secondary energy career that counted as a clean-burning fuel. However, hydrogen suffers from a low volumetric energy density at ambient temperature and pressure. This deficiency has been overcome by “solid-state hydrogen storage” technologies, where the hydrogen is adsorbed/absorbed - depending on the type of materials - on a solid surface. Mixed metal oxides (MMOs) particularly transition-based metal oxides have been recently developed for hydrogen adsorption with a superior affinity for hydrogen. Here, we demonstrated two nanosized-MMOs based on (mono-) perovskite structure, Li₂TiO₃, and LaTiO₃. These two MMOs are successfully synthesized via the auto-combustion method in the presence of starch fuel. After confirmation of their structures and morphologies, the samples are used for electrochemical hydrogen storage in an alkaline medium. The average particle diameters of Li₂TiO₃ and LaTiO₃ are calculated to be around 16.74 and 24.46 nm, respectively. The results indicate a higher discharge capacity of LaTiO₃ nanoperovskites (1140 mAh/g) as compared to Li₂TiO₃ nanoparticles (680 mAh/g); as confirmed primarily by cyclic voltammetry (CV), with the theoretical hydrogen capacities of 4.1% and 2.4%, respectively. We believe that novel MMOs can be potentially fulfilled the requirements of future energy targets, arranged and reported by US-department of energy (DOE).     

Mixed CoS2@Co3O4 composite material: An efficient nonprecious electrocatalyst for hydrogen evolution reaction

Hydrogen evolution reaction (HER) has been identified as a sustainable and environment friendly technology for a wide range of energy conversion and storage applications. The big barrier in realizing this green technology requires a highly efficient, earth-abundant, and low-cost electrocatalyst for HER. Various HER catalysts have been designed and reported, still, their performance is not up to the mark of Pt. Among them, cobalt-based, especially cobalt disulfide (CoS₂) has shown significant HER activity and found suitable candidature for HER due to its low cost, simple to prepare, and exhibits good stability. Herein, we synthesized various nanostructured materials including pure CoS₂, Co₃O₄ and their composites by wet chemical methods and found them active for HER. The scanning electron microscopy (SEM) has revealed a morphology of composite as a mixture of nanowires and round shape spherical nanoparticles with several microns in dimension. The X-ray diffraction (XRD) confirmed the cubic phase of CoS₂ and cubic phase of Co₃O₄ in the composite materials. The chemical deposition of CoS₂ onto Co₃O₄ has tailored the HER activity of CoS₂@Co₃O₄ composite material. Two CoS₂@Co₃O₄ composite materials were produced with varying amounts of Co₃O₄ and labeled as samples 1 and 2. The Co₃O₄ reduced the adsorption energy for hydrogen, decreased the aggregation of CoS₂ and uplifted the stability of CoS₂@Co₃O₄ a composite material in alkaline media. Sample 1 requires an overpotential of 320 mV to reach a current density of 10 mA/cm² and it exhibits a Tafel slope of 42 mVdec⁻¹which is the key indicator for the fast HER kinetics on sample 1. The sample 1 is highly durable for 50 h and also it has excellent stability. The electrochemical impedance spectroscopy (EIS) revealed a small charge transfer resistance of 28.81 Ohms for the sample 1 with high capacitance double-layer value of 0.81 mF. EIS has supported polarization and Tafel slope results. Based on the partial physical characterization and the electrochemical results, the as-obtained sample 1 (CoS₂@Co₃O₄ composite material) will find potential applications in an extended range of energy conversion and storage devices owing to its low cost, high abundance, and excellent efficiency.     

High-performance oxygen electrode Ce0.9Co0.1O2-δ-LSM-YSZ for hydrogen production by solid oxide electrolysis cells

Hydrogen production via solid oxide electrolysis cell (SOEC) is world widely concerned with the new energy revolution. The SOEC performance must be enhanced for the practical application. In this study we report a high-performance Ce_0.9Co_0.1O_2-δ-LSM-YSZ (CC-LSM-YSZ) oxygen electrode, in which Ce_0.9Co_0.1O_2-δ nanoparticles are loaded on LSM-YSZ scaffold and characterized by XRD, SEM, O₂-TPD and H₂-TPR. Under 50% absolute humidity (A.H), the cell with 1CC-LSM-YSZ, 2CC-LSM-YSZ, 3CC-LSM-YSZ and 4CC-LSM-YSZ oxygen electrode delivers a current density of 0.63, 0.94, 1.14 and 1.26A cm^?2 at 1.3 V, which is 1.7, 2.5, 3.0 and 3.3 times higher than the blank LSM-YSZ cell, respectively. The hydrogen generation rate of the 4CC-LSM-YSZ cell is as high as 873 m L cm^?2 h^?1 under 70% A.H. The DRT results demonstrate the accelerated charge transfer reaction on LSM-YSZ-Ce_0.9Co_0.1O_2-δ oxygen electrode. LSM-YSZ-Ce_0.9Co_0.1O_2-δ has the potential for the application of oxygen electrode in SOEC technology.     

Synthesis and characterizations of highly responsive H2S sensor using p-type Co3O4 nanoparticles/nanorods mixed nanostructures

High-quality p-type semiconducting Co₃O₄ with mixed morphology of nanoparticles/nanorods are synthesized using a hydrothermal route for high response and selective hydrogen sulphide (H₂S) sensor application. XRD and Raman studies revealed the crystal structure and molecular bonding for obtained Co₃O_4, respectively. The nanoparticles/nanorods-like structures were confirmed for Co₃O₄ using FESEM and TEM analysis. The EDS and XPS spectra analysis were carried out for elemental composition and chemical atomic states of Co₃O₄. The Co₃O₄ sensor is investigated for gas sensing properties in dynamic conditions. The sensor exhibited the highest selectivity towards H₂S among various hydrogen-contained gases at 225 °C. The sensor revealed a high response of 357% and 44% for 100 and 10 ppm H₂S gas concentrations, respectively. The Co₃O₄ sensor exhibited a systematic dynamic resistance response for 100–10 ppm range H₂S gas. The excellent dynamic resistance repeatability of the sensor was shown towards 25 ppm H₂S gas. The response of Co₃O₄ sensor was investigated at different operating temperatures and H₂S concentrations. The sensor stability and H₂S sensing mechanism for the Co₃O₄ sensor have been reported. Highly uniform and mixed nanostructures of Co₃O₄ can be the potential sensor material for real-time high-performance H₂S sensor application.     

Facile one-step in-situ encapsulation of non-noble metal Co2P nanoparticles embedded into B,N, P tri-doped carbon nanotubes for efficient hydrogen evolution reaction

Developing high performance, good stability and noble-metal-free electrocatalysts for renewable hydrogen evolution reaction (HER) remain a substantial challenge. Herein, we introduce a novel facile one-step in-situ strategy through pyrolysis for the synthesis of Co₂P nanoparticles encapsulated Boron, Nitrogen, and Phosphorous tri-doped carbon nanotubes (Co₂P/BNP-CNTs). The synergetic effect between Co₂P nanoparticles and heteroatom doped CNTs contributes to the remarkable HER performance. The Co₂P/BNP-CNT-900 electrocatalyst shows a low overpotential of 133 mV at a current density of 10 mA cm⁻² and a small Tafel slope of 90 mV dec⁻¹ in 0.1 M KOH media. More importantly, the Co₂P/BNP-CNT-900 electrocatalyst exhibits superior long-term stability in alkaline solution at −0.25 V versus Reversible Hydrogen Electrode (RHE) for 15 h and up to 1000 cycles with negligible performance loss. Overall, our works suggest a one-pot facile synthesis strategy for rational designing high-performance electrocatalysts with enhanced HER performance.     

The preparation of Co9S8 and CoS2 nanoparticles by a high energy ball-milling method and their electrochemical hydrogen storage properties

Two different Co–S compounds with enhanced hydrogen storage properties, Co₉S₈ and CoS₂, were prepared by ball-milling mixtures of Co metal and S powder. X-ray diffractometry, scanning electron microscopy and transmission electron microscopy were used to show that specific molar ratios of Co:S and ball-milling speeds and times result in pure Co₉S₈ and CoS₂, thus overcoming a long-standing inability to obtain pure Co–S compounds via ball-milling. A galvanostatic charge–discharge process and cyclic voltammetry measurements showed that the as-obtained Co₉S₈ and CoS₂ nanoparticles have enhanced electrochemical hydrogen storage capacities of 1.79 and 1.57 wt% hydrogen, respectively, which are higher than those previously reported. In addition, based on the corresponding X-ray photoelectron spectroscopy and cyclic voltammetry measurements, a new electrochemical hydrogen storage mechanism for the two Co–S compounds was proposed and discussed.     

Two step synthesis of TiO2–Co3O4 composite for efficient oxygen evolution reaction

For an active hydrogen gas generation through water dissociation, the sluggish oxygen evolution reaction (OER) kinetics due to large overpotential is a main hindrance. Herein, a simple approach is used to produce composite material based on TiO₂/Co₃O₄ for efficient OER and overpotential is linearly reduced with increasing amount of TiO₂. The scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) investigations reveal the wire like morphology of composite materials, formed by the self-assembly of nanoparticles. The titania nanoparticles were homogenously distributed on the larger Co₃O₄ nanoparticles. The powder x-ray diffraction revealed a tetragonal phase of TiO₂ and the cubic phase of Co₃O₄ in the composite materials. Composite samples with increasing TiO₂ content were obtained (18%, 33%, 41% and 65% wt.). Among the composites, cobalt oxide-titanium oxide with the highest TiO₂ content (CT-20) possesses the lowest overpotential for OER with a Tafel slope of 60 mV dec^?1 and an exchange current density of 2.98 × 10^?3A/cm². The CT-20 is highly durable for 45 h at different current densities of 10, 20 and 30 mA/cm². Electrochemical impedance spectroscopy (EIS) confirmed the fast charge transport for the CT-20 sample, which potentially accelerated the OER kinetics. These results based on a two-step methodology for the synthesis of TiO₂/Co₃O₄ material can be useful and interesting for various energy storage and energy conversion systems.     

Effect of Fe,Ni and Zn dopants in La0·9Sr0·1CoO3 on the electrochemical performance of single-component solid oxide fuel cell

Fe-, Ni- and Zn- doped La_0·9Sr_0·1CoO₃ are prepared and a single-component solid oxide fuel cell composed of 30 wt% perovskite oxide and 70 wt% samarium-doped ceria (SDC)-(Li_0·67Na_0.33)₂CO₃ is fabricated and characterized. When doping with either Fe, Ni or Zn, most cations occupy the Co³⁺ sites. X-ray photoelectron spectroscopy and oxygen temperature-programmed desorption characterizations show that Zn-doped La_0·9Sr_0·1CoO₃ exhibits notably high surface oxygen, causing higher catalytic activity for oxygen reduction reaction (ORR) than that of nondoped La_0·9Sr_0·1CoO₃. Fe or Ni doping into La_0·9Sr_0·1CoO₃ decreases surface oxygen, resulting in a lower catalytic activity toward ORR than La_0·9Sr_0·1CoO₃. Furthermore, X-ray diffraction, temperature-programmed reduction and transmission electron microscopy characterizations prove that after reduction, Fe-doped La_0·9Sr_0·1CoO₃ is reduced to Co_0·72Fe_0.28 alloy-oxide core-shell nanoparticles, resulting in a high catalytic activity for hydrogen oxygen reaction (HOR). However, NiCo₂O₄ are formed during the reduction of Ni-doped La_0·9Sr_0·1CoO₃, exhibiting a low catalytic activity for the HOR. Similarly, the low catalytic activity of reduced Zn-doped La_0·9Sr_0·1CoO₃ for the HOR is caused by the formation of ZnCo₂O₄. A single component fuel cell composed with Fe-doped La_0·9Sr_0·1CoO₃-SDC-(Li_0·67Na_0.33)₂CO₃ exhibits the highest P_max of 239.1 mW cm⁻² at 700 °C with H₂ as fuel, indicating that HOR processes are rate-determining steps.     

Investigation of La0.6Sr0.4Co1-xNixO3-δ (x=0, 0.2, 0.4, 0.6, 0.8) catalysts on solid oxide fuel cells anode for biogas dry reforming

The introduction of catalyst on anode of solid oxide fuel cell (SOFC) has been an effective way to alleviate the carbon deposition when utilizing biogas as the fuel. A series of La_0.6Sr_0.4Co_1-xNi_xO_3-δ (x = 0, 0.2, 0.4, 0.6, 0.8) oxides are synthesized by sol-gel method and used as catalysts precursors for biogas dry reforming. The phase structure of La_0.6Sr_0.4Co_1-xNi_xO_3-δ oxides before and after reduction are characterized by X-ray diffraction (XRD). The texture properties, carbon deposition, CH₄ and CO₂ conversion rate of La_0.6Sr_0.4Co_1-xNi_xO_3-δ catalysts are evaluated and compared. The peak power density of 739 mW cm^?2 is obtained by a commercial SOFC with La_0.6Sr_0.4Co_0.4Ni_0.6O_3-δ catalyst at 850 °C when using a mixture of CH₄: CO₂ = 2:1 as fuel. This shows a great improvement from the cell without catalyst for internal dry reforming, which is attributed to the formation of NiCo alloy active species after reduction in H₂ atmosphere. The results indicate the benefits of inhibiting the carbon deposition on Ni-based anode through introducing the La_0.6Sr_0.4Co_0.4Ni_0.6O_3-δ catalyst precursor. Additionally, the dry reforming technology will also help to convert part of the exhaust heat into chemical energy and improve the efficiency of SOFC system with biogas fuel.     

Coral reef structured cobalt-doped vanadate oxometalate nanoparticle for a high-performance electrocatalyst in water splitting

Facing the energy crisis in the whole world, it is important to decompose water to obtain high-clean hydrogen energy. However, water splitting by electrocatalysis is suffering from high voltage and poor stability. Herein, we synthesize Co₃V₂O₈ coral reef-like nanoparticles in a facile way, showing a low oxygen evolution reaction (OER) overpotential of 318 mV coupled with good stability, which is superior to commercial RuO₂. Besides, the Co₃V₂O₈ shows fast kinetics for hydrogen evolution reaction (HER) and small impedance. Furthermore, the Co₃V₂O₈ nanoparticles are assembled in symmetric two-electrode system, which has a very low overall water splitting voltage of 1.50 V at 10 mA cm^?2, this value surpasses the benchmark RuO₂//Pt/C assembling and most of the other oxometalate-based electrocatalysts. This work provides a novel and facile way of preparing oxometalates nanomaterial electrocatalyst for hydrogen energy.     

A high-performance ternary ferrite-spinel material for hydrogen storage via chemical looping redox cycles

Chemical looping has been proposed as an emerging technology for large-scale hydrogen storage with the advantages of high volumetric hydrogen storage density, environmental compatibility, and safety. However, to ensure sufficient redox activity, conventional oxygen carrier materials must be operated at a temperature higher than 800 °C, leading to the rapid deterioration on the storage capacity over several cycles. In this work, we report a ternary ferrite-spinel material Cu_0.5Co_0.5Fe₂O₄ for chemical looping hydrogen storage and production. The material exhibits high volumetric hydrogen storage density (65.58 g·L⁻¹) and average hydrogen production rate (142 μmol·g⁻¹·min⁻¹) at 550 °C. The performance is maintained with negligible deactivation over repetitive redox cycles. The high performance can be attributed to the ability of Cu and Co to improve the reduction and the reversible phase change during the oxidation stage at moderate temperatures. The performance of the Cu_0.5Co_0.5Fe₂O₄ is comparable to the state-of-the-art Rh-FeO_x containing rare earth metals, which enables its potential in industry application.     

Cost-effective synthesis of carbon loaded Co3O4 for controlled hydrogen generation via NaBH4 hydrolysis

The simple, reliable, and economical process of combustion is used to synthesize carbon loaded cobalt oxide (C–Co₃O₄) for hydrogen generation via NaBH₄ hydrolysis. The effect of NaBH₄ concentration, pH, and temperature of the solution on hydrogen generation is investigated in detail. C–Co₃O₄ exhibits zero order reaction kinetics with respect to NaBH₄ concentration. A stable Hydrogen Generation Rate (HGR) is observed throughout the reaction in the temperature range of 300–315 K using C–Co₃O₄. It is found that 0.01 g of C–Co₃O₄ exhibited high reaction activity with a maximum HGR of 5430 ml min^?1 g^?1 for the optimal solution at 320 K. The activation energy is calculated to be 55.9 kJ mol^?1 for hydrolysis of NaBH₄ using C–Co₃O₄. The present study provides an economical method for the large-scale production of C–Co₃O₄ for hydrogen generation from NaBH₄ hydrolysis, which can pave the way to commercialize hydrogen as a main source of fuel.     

Synthesis of potential nanostructures based on strontium hexaferrite for electrochemical hydrogen storage

Today, the reduction of fossil fuel resources and the increase of their destructive environmental effects are important challenges. One strategy to this problem is application of new sources of energy supply. Hydrogen can play an important role in future energy supplies due to its unique properties such as clean combustion and high energy content relative to mass. In addition, hydrogen is considered as a green energy because it can be produced from renewable sources and is not polluting. The most important issue in hydrogen as a fuel is its storage. Hydrogen must be stored reversibly in a completely safe manner as well as with high storage efficiencies. One of the best ways to store hydrogen is using of new nanostructured adsorbents. In this study, first strontium hexaferrite (SrFe₁₂O₁₉) nanostructures are synthesized by sol-gel auto-combustion method. Then, the samples structure is studied using various techniques. Furthermore, the nanostructures are used as hydrogen storage materials. Using electrochemical techniques, the hydrogen storage properties of the materials are investigated in alkaline media. The obtained electrochemical results show that the maximum hydrogen storage capacity of SrFe₁₂O₁₉ nanostructures is about 3100 mAh/g.     

Tuning the alloy degree for Pd-M/Al2O3 (M=Co/ Ni /Cu) bimetallic catalysts to enhance the activity and selectivity of dodecahydro-N-ethylcarbazole dehydrogenation

Hydrogen is a promising candidate to substitute the fossil fuels. However, the efficient hydrogen storage technologies restrict the commercial applications. Developing new catalysts with high activity and selectivity is important for the dehydrogenation reaction in N-ethylcarbazole/dodecahydro-N-ethylcarbazole (NECZ/12H-NECZ) hydrogen storage system. In this work, a series of Pd-M/Al₂O₃ (M = Co, Ni and Cu) bimetallic catalysts are synthesized successfully and show good performance in the dehydrogenation reaction of 12H-NECZ than the commercial Pd/Al₂O₃ catalyst. The Pd₁Co₁/Al₂O₃ catalyst (Practical Pd content = 2.4136 wt%) showed the highest catalytic performance with 95.34% H₂ release amount, TOF of 230.5 min⁻¹ and 85.4% selectivity of NECZ. Combined with the characterization analysis, it can be proposed that the dehydrogenation performance of 12H-NECZ is dependent on the alloy phases, reasonable electronic structures and nanoparticle size of catalysts. The fine-tuned alloy degree and appropriate nanoparticle size of Pd₁Co₁/Al₂O₃ bring the 17.7% increase of H₂ release amount and 99.5% increase of NECZ selectivity than those of Pd/Al₂O₃. For the bimetallic catalysts, the enhancement of selectivity of NECZ is mainly from the increase of the kinetic constant of rate-limiting step.     

Co3O4 nanoparticles decorated Polypyrrole/carbon nanocomposite as efficient bi-functional electrocatalyst for electrochemical water splitting

An effective bi-functional electrocatalyst of Co₃O₄/Polypyrrole/Carbon (Co₃O₄/Ppy/C) nanocomposite was prepared through a simple dry chemical method and used to catalyze the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Three types of carbon support as Vulcan carbon, reduced graphite oxide (RGO) and multi-walled carbon nanotubes (MCNTs) were used to study the influence on electrochemical reactions. Spherical shaped Co₃O₄ nanoparticles with 8–10 nm was found uniformly distributed on Ppy/C composite, which were analyzed by X-ray diffraction and transmission electron microscopy techniques. Amongst, Co₃O₄/Ppy/MWCNT shows improved bifunctional electrocatalytic activity towards both OER and HER with relatively low over potential (340 mV vs. 490 mV at 10 mA cm⁻²) and Tafel slope (87 vs. 110 mV dec⁻¹). In addition to that, MWCNT supported Co₃O₄/Ppy nanocomposite exhibits good electronic conductivity and electrochemical stability up to 2000 potential cycles. The results clearly indicate that the Co₃O₄/Ppy/MWCNT nanocomposite could be the promising bi-functional electrocatalyst for efficient water electrolysis.     

The different effect of Co3O4 or/and carbon fiber originated from biomass on the electrochemical hydrogen storage performance of Co2B alloy

Co₂B alloy was synthesized via the method of high temperature solid phase. Carbon fiber (CF) was prepared from cotton by calcination process. The addition of carbon fiber and Co₃O₄ improves corrosion resistance and charge transfer speed of the composite material electrode. The R_ct value of Co₂B + 1 wt.% CF was 360 mΩ, lower than the other composite electrode could reduce charge transfer resistance. The overall electrochemical performance of Co₂B + 2 wt.% Co₃O₄ + 1 wt.% CF was best among all the electrodes, and its C_max could reach 715.3 mAh/g. The high conductivity and multiple reaction sites provided by carbon fiber and the catalytic effect of Co₃O₄ may be the main reasons for the improvement of electrochemical performance, which enhance the kinetic performance of electrochemical reactions. The synergistic effect of carbon fiber and Co₃O₄ improves the electrochemical hydrogen storage properties of Co₂B alloy. This work presents a simple and effective method to improve the electrochemical hydrogen storage performance of cobalt-boron alloys by adding transition metal oxides and carbon materials derived from biomass.     

Mechanical alloying preparation of fullerene-like Co3C nanoparticles with high hydrogen storage ability

Fullerene-like orthorhombic-structured Co₃C nanoparticles have been synthesized by direct ball-milling of Co and graphene (GE) powders with different Co/GE weight ratios. Electrochemical measurements showed that the Co₃C nanoparticles displayed excellent electrochemical hydrogen storage capacities and the maximum capacity reached 1415 mA h/g (5.176 wt% hydrogen) at room temperature and ambient pressure. The reaction mechanism and the reasons for the differences of the Co₃C electrodes were also investigated. It was found that the quasi-reversible Co₃CH_x/Co₃C reaction was dominant for all the Co₃C electrodes.     

Nano-structured (La, Sr)(Co, Fe)O3 + YSZ composite cathodes for intermediate temperature solid oxide fuel cells

A nano-structured La_0.8Sr_0.2Co_0.5Fe_0.5O₃ + Y₂O₃ doped ZrO₂ (LSCF + YSZ) composite cathode was prepared by impregnation of a LSCF-containing solution into porous YSZ structure presintered on the YSZ electrolyte. The result shows that the LSCF phase was formed at 700 °C, forming a nano-structured, effective and functional LSCF + YSZ composite cathode that not only produces high triple phase boundaries for the O₂ reduction reaction, but also provides a structurally stable interface between the LSCF and YSZ. The electrode polarization resistance for the O₂ reduction reaction is from 0.539 to 0.047 Ω cm² between 600 and 750 °C, indicating the promising potential the LSCF + YSZ as a high performance cathode for intermediate temperature solid oxide fuel cells.