Ce0.7Bi0.3O1.85-(La0.8Sr0.2)0.9MnO3-Y0.16Zr0.84O1.92 ternary cathodes for low temperature solid oxide fuel cells

The ternary cathodes of Ce_0.7Bi_0.3O_1.85-(La_0.8Sr_0.2)_0.9MnO₃-Y_0.16Zr_0.84O_1.92 (BDC-LSM-YSZ) are fabricated through infiltration for low temperature solid oxide fuel cells. The infiltrated BDC particles are 10–20 nm in size and cover on LSM and YSZ particles. The 10 wt% and 20 wt% BDC-LSM-YSZ samples show a large peak for the desorption of surface oxygen species and a large peak for the evolution of lattice oxygen, reflecting their good redox property. 0.1BDC-LSM-YSZ cell and 0.2BDC-LSM-YSZ cell give the power density at 0.6 V of 387.8 and 521.7 mWcm^?2 at 600 °C, which is 3.7 and 4.9 times higher than that of LSM-YSZ cell, respectively. 0.1BDC-LSM-YSZ cell and 0.2BDC-LSM-YSZ cell exhibit low ohmic resistance and low total polarization resistance. The DRT analysis reveals that charge transfer reaction and surface diffusion are greatly accelerated on the BDC-LSM-YSZ cathodes.     

Influence of Ag nanoparticles on state of the art MnO2 nanorods performance as an electrocatalyst for lithium air batteries

The need for an alternative and efficient electrocatalyst to replace Pt-based noble materials is a goal of prime importance in Li– air battery technology. In this work, novel silver nanoparticles-incorporated MnO₂ nanorods as an air electrode bifunctional catalyst have been synthesized by a simple polyol method. The physical characteristics of the thus prepared materials are analyzed by X-ray diffraction (XRD), SEM, and Brunauer–Emmett–Teller (BET) techniques. These analyses confirmed the successful synthesis of 20 to 25 nm-sized different weight % Ag nanoparticles incorporated on α-MnO₂ nanorods. Linear sweeping voltammetric results of AgMnO₂ showed improved ORR performance as compared to α- MnO₂ nanorods in terms of the onset potential, half wave potential and limiting current. The addition of catalysts has significantly increased the discharge capacity and overall performance of the cells. The first discharge curve of 5 wt% Ag MnO₂ sample reached a maximum capacity of 3500 mAhg-1 at 2.0 V with a current density of 0.1 mA cm^?2 with a plateau between 2.7 and 2.6 V. Long term stability of increasing weight percentage of Ag nanoparticles on MnO₂ samples is increased.     

Degradation mechanism of layered MnO2 cathodes in Zn/ZnSO4/MnO2 rechargeable cells

Layered-type MnO₂ (δ- or naturally occurring birnessite-related MnO₂) electrodes that suffer capacity degradation during extended cycling in Zn/ZnSO₄/MnO₂ rechargeable cells are investigated. When the composite cathodes consisting of MnO₂ powder, carbon additive and Teflon binder are galvanostatically cycled in the potential range of 1.0–1.9 V (vs. Zn/Zn²⁺) where a two-step, two-electron charge/discharge reaction occurs, the cathodes lose their capacities within a few cycles. Such an abrupt capacity loss is found to be caused partly by the formation of basic zinc sulfates (BZS, ZnSO₄·3Zn(OH)₂·nH₂O) on the cathode surface, and also by the Mn losses due to the irreversible nature of the cathodic cell reaction: Mn²⁺ ions, once produced during the discharge step, are not fully restored to MnO₂ during the charging period. An addition of 0.1–0.5 M MnSO₄ to 2 M ZnSO₄ electrolyte, however, greatly alleviates these failure modes. With this addition, the Mn losses become insignificant as a result of facilitation in the charging reaction and BZS formation is discouraged. Carbon additives loaded in the composite MnO₂ cathodes also critically affect the cathode cyclabilities by controlling the rate of charging reaction: the cathodes loaded with acetylene blacks display superior cyclabilities to those containing furnace blacks. From one observation whereby the acetylene blacks possess a lesser amount of surface oxygenic species than the furnace blacks and the other whereby the charging reaction more readily occurs in the former cathodes, it is proposed that the charging (deposition) reaction is significantly hindered by the presence of surface oxygenic species on carbon additives. Electron micrographs of cycled MnO₂ cathodes reveal that larger and porous MnO₂ deposits are well-grown on the acetylene-black-loaded cathodes whereas only irregular-shaped smaller deposits are formed on the furnace-black-loaded cathodes.     

Functionalised hybrid Poly(ether ether ketone) containing MnO2: Investigation of operative conditions for hydrogen sorption

A composite material synthesis, based on Manganese oxide (MnO₂) anchored to a functionalized polymeric matrix, was optimized. For this investigation two different MnO₂ loadings were selected (16 and 80 wt%) in order to understand the relation between the oxide content, chemical-physical characteristic and the H₂ sorption properties. SEM, XRD were carried out and the obtained results were correlated to the H₂ sorption/desorption characterizations by Sievert apparatus.From these measurements at 50 °C/40 bar, the sample containing 16 wt% of metal oxide content has revealed a low H₂ sorption capability (0,04 wt%), while the 80 wt% sample showed a very high H₂ storage value (3 wt%). A short sorption/desorption cycles were carried out and a good reversibility was revealed.A modelling study, ab-initio Density Functional Theory (DFT) calculations, was carried out. The starting unit cell was MnO₂ while Mn₂₄O₄₈ was considered as a supercell. The number of H atoms was gradually increased and desorption energy was calculated. Desorption energy starts from 366 kJ/mol and decreases by increasing the number of H atoms. For the experimental H₂ sorption value (1,7 wt%) it was calculated the number of the respective H atoms (36) and the corresponding desorption energy (150 kJ/mol).     

High power BaFe(VI)O4/MnO2 composite cathode alkaline super-iron batteries

This short communication demonstrates that not only pure Fe(VI) cathodes, but also MnO₂/Fe(VI) composite cathodes can substantially enhance the high power discharge of alkaline batteries. The 2.8 Ω and 0.7 W high power discharge of alkaline cells are investigated for 3:1 and 1:1 composite MnO₂/BaFeO₄ cathode cells, provide discharge energies intermediate to that found in the (non-composite) BaFeO₄ cathode cell. At a constant 2.8 Ω load, the 1:1 composite MnO₂/BaFeO₄ cell delivers up to 40% higher energy capacity than the MnO₂ pure cathode alkaline cell, and up to three-fold the capacity of the constant 0.7 W power MnO₂ discharge.     

Enhancement of the electrochemical performance of free-standing graphene electrodes with manganese dioxide and ruthenium nanocatalysts for lithium-oxygen batteries

Hybrid ternary Graphene/Ruthenium/α-MnO₂ (rGO/Ru/α-MnO₂) flexible nanocomposite cathodes were fabricated via controlling both reduction and vacuum filtration processes without using a binder and conductive carbon additives for flexible Li-air battery system. To compare the electrochemical performance of the Graphene/Ruthenium/α-MnO₂ cathodes, bare rGO and rGO/Ru free-standing cathodes were also manufactured. rGO cathodes with well-dispersed α-MnO₂ nanowires and ruthenium nanoparticles were successfully synthesized and shown to dramatically increase (decrease) oxygen reduction (evolution) reactions. The enhancement on the electrochemical performance of the synthesized cathodes was attributed not only to catalysis effect of ruthenium and α-MnO₂ but also well-stacked morphology of the nanocomposite architecture which enables increased oxygen flow between the layers and, hence boosted reaction kinetics.Physical characterization of the cathodes was carried out using FESEM, EDS, TEM, XRD, XPS and Raman spectroscopy. The discharge product of the cathodes was also evaluated using TEM and XPS. Electrochemical performances of the cathodes were evaluated by means of CV, EIS, galvanostatic charge-discharge and electrochemical cycling tests. Thanks to the synergetic effect of Ruthenium and α-MnO₂ catalysts, our ternary rGO/Ru/α-MnO₂ cathodes were shown to serve full discharge capacity of 2225 mAh/g while rGO/Ru can deliver only 1670 mAh/g. Besides, the cycling stability of the ternary rGO/Ru/α-MnO2 cathodes was shown for 50 cycles at 650 mAh/g capacity limited tests in assembled Li–O2 batteries.     

Fabrication and characterisation of the graphite bi-polar plates used in A 0.25 kW PAFC stack

The graphite bi-polar plates were fabricated using lamination technique with polyether sulfone (PES) films (50 μm) and graphite foils (400 μn) in between the two porous graphite plates (CBC) by keeping in a specially designed and fabricated fixture with stainless steel plates at the top and bottom. The fixture was then kept in an hydraulic hot press, at loads of 10–20 tons, and heat treated at 410 °C for 30 min. Then these graphite plates were sized to 30 cm × 20 cm × 0.64 cm, leaving 0.4 mm thick graphite foil at the centre of the plate, to avoid the intermixing of the hydrogen and oxygen/air. While, the gas permeability (cm²/sec) of the plates was determined, with N₂ gas using differential pressure method, their electrical resistivity (mΩm) was measured using milliohmmeter and passing DC current to the graphite plates, at loads from 1–5 kgs. The values of permeability and electrical resistivity of the plates are found to be lower than 0.01 cm²/sec and 4–14 mΩm respectively. A stack with 6 cells was assembled using the in house developed graphite bi-polar plates, anodes and cathodes with matrix, to generate a DC power of 0.25 kW (3.6 V × 71.0 amps). It was operated for 300 h successfully using H₂ and Air, 1 bar, at 175 °C. In this paper, the detailed fabrication method of graphite bi-polar plates and their characteristics of gas permeability, electrical resistivity and the results of the 0.25 kW PAFC stack operation are presented.     

Hydrogen storage properties of activated carbon confined LiBH4 doped with CeF3 as catalyst

CeF₃ as a catalyst is first added to activated carbon (AC) by ball milling under low rotation speed. Then the treated AC was used as the scaffold to confine LiBH₄ by melt infiltration process. The combined effects of confinement and CeF₃ doping on the hydrogen storage properties of LiBH₄ are studied. The experimental results show that LiBH₄ and CeF₃ are well dispersed in the AC scaffold and occupy up to 90% of the pores of AC. Compared with pristine LiBH₄, the onset dehydrogenation temperature for LiBH₄-AC and LiBH₄-AC-CeF₃ decreases by 150 and 190 °C, respectively. And the corresponding dehydrogenation capacity increases from 8.2 wt% to 13.1 wt% for LiBH₄-AC and 12.8 wt% for LiBH₄-AC-CeF₃, respectively. The maximum dehydrogenation speed of LiBH₄-AC and LiBH₄-AC-CeF₃ is 80 and 288 times higher than that of pristine LiBH₄ at 350 °C. And LiBH₄-AC andLiBH₄-AC-CeF₃ show good reversible hydrogen storage properties. On the during 4th dehydrogenation cycle, the hydrogen release capacity of LiBH₄-AC and LiBH₄-AC-5 wt% CeF₃ reaches 8.1 and 9.3 wt%, respectively.     

Microbial electrolysis cell powered by an aluminum-air battery for hydrogen generation,in-situ coagulant production and wastewater treatment

Microbial electrolysis cells (MECs) are an efficient technology for generating hydrogen gas from organic matters, but an additional voltage is needed to overcome the thermodynamic barrier of the reaction. A combined system of MEC and the aluminum-air battery (Al-air battery) was designed for hydrogen generation, coagulant production and operated in an energy self-sufficient mode. The Al-air battery (28 mL) produced a voltage ranged from 0.58 V to 0.80 V, which powered an MEC (28 mL) to produce hydrogen. The hydrogen production rate reached 0.19 ± 0.01 m³ H₂/m³/d and 14.5 ± 0.9 mmol H₂/g COD. The total COD removal rate was 85 ± 1%, of which MEC obtained 75 ± 1% COD removal and 10 ± 1% COD removal was achieved by in-situ coagulating process. The microorganisms removal of MEC effluent was 97 ± 2% through ex-situ coagulating process. These results showed that the Al-air battery-MEC system can be operated in energy self-sufficient mode and recovered energy from wastewater with high quality effluent.     

Synthesis,characterization, and electrochemical performance of the ternary layered composite (1-x-y) LiNi1/3Co1/3Mn1/3O2·xLi2MnO3·yLiCoO2

Composite ceramic cathodes represented by the formula (1-x-y) LiNi_1/3Co_1/3Mn_1/3O₂·xLi₂MnO₃·yLiCoO₂ were studied. A ternary compositional diagram was built with these ceramic materials as end-members, and selected points were chosen to represent the compositional space. Synthesized ceramic composite materials were investigated as to whether integration of structurally compatible units leads to improved electrochemical performance. Detailed structural (X-ray diffraction – XRD), elemental (X-ray photoelectron spectroscopy-XPS), microstructure (Scanning electron microscopy – SEM), and electrochemical (galvanostatic testing of half-cells) studies were performed and are presented. Within eight samples studied three compositions are found to exhibit first discharge capacity of around 230 mAh/g.     

A La0.8Sr0.2MnO3/La0.6Sr0.4Co0.2Fe0.8O3−δ core–shell structured cathode by a rapid sintering process for solid oxide fuel cells

A La_0.8Sr_0.2MnO₃ (LSM)/La_0.6Sr_0.4Co_0.2Fe_0.8O_3?δ (LSCF) core–shell structured composite cathode of solid oxide fuel cells (SOFCs) has been fabricated by wet infiltration followed by a rapid sintering (RS) process. The RS is carried out by placing LSCF infiltrated LSM electrodes directly into a preheated furnace at 800 °C for 10 min and cooling down very quickly. The heating and cooling step takes about 20 s, substantially shorter than 10 h in the case of conventional sintering (CS) process. The results indicate the formation of a continuous and almost non-porous LSCF thin film on the LSM scaffold, forming a LSCF/LSM core–shell structure. Such RS-formed infiltrated LSCF–LSM cathodes show an electrode polarization resistance of 2.1 Ω cm² at 700 °C, substantially smaller than 88.2 Ω cm² of pristine LSM electrode. The core–shell structured LSCF–LSM electrodes also show good operating stability at 700 °C and 600 °C over 24–40 h.     

Investigation on gaseous and electrochemical hydrogen storage performances of as-cast and milled Ti1.1Fe0.9Ni0.1 and Ti1.09Mg0.01Fe0.9Ni0.1 alloys

The AB-type Ti_1.1Fe_0.9Ni_0.1 (Mg₀ for short) and Ti_1.09Mg_0.01Fe_0.9Ni_0.1 (Mg_0.01 for short) alloys were fabricated by vacuum induction melting and mechanical milling. The effects of partly substituting Ti with Mg and/or mechanical milling on the structure, morphology, gaseous thermodynamics and kinetics, and electrochemical performances were studied. The results reveal that the as-cast Mg₀ alloy contains the main phase TiFe and a small number of TiNi₃ and Ti₂Ni phases. Substituting Ti with Mg and/or mechanical milling results in the disappearance of the secondary phases. The discharge capacities of the as-cast Mg₀ and Mg_0.01 alloys are 12.6 and 8.8 mAh g^?1, which increase to 52.6 and 80.4 mAh g^?1 after 5 h of mechanical milling. By milling the as-cast alloy powders with carbonyl nickel powders, they are greatly enhanced to 191.6 mAh g^?1 for the Mg₀+7.5 wt% Ni alloy and 205.9 mAh g^?1 for the Mg_0.01+5 wt% Ni alloy at the current density of 60 mA g^?1, respectively. The values of dehydrogenation enthalpy (ΔH_des) and dehydrogenation activation energy (E^des_(a)) are very small, meaning that the thermal stability and the desorption kinetics of the hydrides are not the key influence factors for the discharge capacity. The reduction of the particle size and the generation of the new surfaces without oxide layers have slight improvements on the discharge capacity, while the enhancement of the charge transfer ability of the surfaces of the alloy particles can significantly promote the electrochemical reaction of the alloy electrodes.     

Enhanced electrocatalytic activity of NiO nanoparticles supported on graphite planes towards urea electro-oxidation in NaOH solution

Nickel oxide nanoparticles are fabricated onto graphite planes [NiO/Gt] by chemical precipitation of Ni(OH)₂ particles with consecutive calcination at 400 °C. The formed electrocatalysts are characterized using X-ray diffraction (XRD) and Transmission electron microscopy (TEM). TEM images demonstrate the deposition of NiO nanoparticles on graphite surface through their crystallite lattice fringes with spacing values of 2.45 Å (111), 2.10 Å (200) and 1.48 Å (220). The electrocatalytic activity of NiO/Gt electrocatalyst is examined towards urea electro-oxidation in NaOH solution using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Urea oxidation peak current density is observed at NiO/Gt electrocatalyst containing 15 wt% NiO [NiO/Gt?15] at a potential value of +640 mV (Ag/AgCl) with a current density value of 17.63 mA cm^?2. The loading amount of NiO in the prepared electrocatalyst significantly affects its electrocatalytic performance. NiO/Gt?15 exhibits the highest urea oxidation current density with the desired stability. The lower Tafel slope, charge transfer resistance and the higher exchange current density and diffusion coefficient values of urea molecules at NiO/Gt?15 surface elect its application as a promising electrocatalyst material during urea oxidation reaction in fuel cells.     

Effects of annealing temperature on the structure and properties of the LaY2Ni10Mn0.5 hydrogen storage alloy

The effects of annealing at 1123, 1148, 1173 and 1198 K for 16 h on the structure and properties of the LaY₂Ni₁₀Mn_0.5 hydrogen storage alloy as the active material of the negative electrode in nickel–metal hydride (Ni–MH) batteries were systematically investigated by X-ray diffraction (XRD), scanning electron microscopy linked with an energy dispersive X-ray spectrometer (SEM–EDS), pressure-composition isotherms (PCI) and electrochemical measurements. The quenched and annealed LaY₂Ni₁₀Mn_0.5 alloys primarily consist of Ce₂Ni₇- (2H) and Gd₂Co₇-type (3R) phases. The homogeneity of the composition and plateau characteristics of the annealed alloys are significantly improved, and the lattice strain is effectively reduced. The alloys annealed at 1148 K and 1173 K have distinctly greater hydrogen storage amounts, 1.49 wt% (corresponding to 399 mAh g^?1 in equivalent electrochemical units) and 1.48 wt%, respectively, than the quenched alloy (1.25 wt%, corresponding to 335 mAh g^?1 in equivalent electrochemical units). The alloys annealed at 1148 K and 1173 K have relatively good activation capabilities. The annealing treatment slightly decreases the discharge potentials of the alloy electrodes but markedly increases their discharge capacity. The maximum discharge capacities of the annealed alloy electrodes (372–391 mAh g^?1) are greater than the extreme capacity of the LaNi₅-type alloy (370 mAh g^?1). The cycling stability of the annealed alloy electrodes was improved.     

Palladium-ruthenium alloy nanoparticles dispersed on CoWO4-doped graphene for enhanced methanol electro-oxidation

Highly dispersed nanoparticles (NPs) of Pd and Pd-Ru alloys on the 10 wt% CoWO₄-doped GNS (graphene nano sheets) support have been obtained by a microwave-assisted polyol reduction and investigated for their application as efficient electrode materials for methanol oxidation reaction (MOR). Structural and electrocatalytic surface characterization of hybrid materials were carried out by XRD, TEM, XPS, cyclic voltammetry and chronoamperometry. Pure CoWO₄ and CoWO₄-doped GNS follow the monoclinic crystal structure and the Pd NPs (6–7 nm) dispersed on CoWO₄-doped GNS follow the face-centered cubic crystal structure. It is observed that with the increase of Pd loading from 5 to 20 mg on the support, the onset potential (E_op) for MOR shifts negatively and the MOR current density increases, the magnitude of shift in E_op and increase in the MOR peak current density being the greatest in the case of 15 mg Pd loading. Introduction of Ru from 0.6 to 2.0 mg into 15 mg Pd on the catalyst support, the apparent activity of the active catalyst, 15Pd/10 wt% CoWO₄-GNS improved further, the magnitude of improvement, however, being the greatest (≈50%) with 1.0 mg Ru. Thus, novel 15Pd-1.0Ru/10 wt%CoWO₄-doped GNS can be a promising electrode material for MOR in alkaline solutions.     

Effects of friction stir processing on hydrogen storage of ZK60 alloy

In this paper we report the use of a novel processing route to produce samples for use as a hydrogen carrier. ZK60 alloy was produced by induction melting and sheets taken from the melt ingot were submitted to Friction Stir Processing (FSP) and subsequent manual filing with a rasp under ambient conditions. Samples from the Base Metal As-Cast (AC) and Stir Zone (SZ) were microstructurally investigated before and after filing including the alloy in as-cast state. The results showed that before filing SZ and AC samples presented equiaxial grains with the SZ sample having a much finer microstructure compared to AC. The values of grain sizes are around 150 μm and 1–2 μm for the AC and SZ samples, respectively. After filing, both samples presented similar grain sizes of only 60 nm. Although they attained similar grain sizes, the filings from SZ were more homogeneous and presented thinner innerlayers compared to its AC counterpart. The filings taken out from the SZ presented much faster kinetics for hydrogen absorption mainly due to its thinner innerlayers and its finer second-phase particle distribution, reaching up to 4.5 wt% of hydrogen uptake against only 1.0 wt% for AC sample after 10 h of absorption in the first cycle. Both samples presented similar behavior for full discharge time. These results show the possibility of using FSP with subsequent filing as a mean to obtain materials with suitable properties for use as energy carriers with enhanced kinetics and better oxidation resistance in shorter processing times.     

Enhanced hydrogen storage kinetics in Mg@FLG composite synthesized by plasma assisted milling

Mg-based materials as potential hydrogen storage candidates, however, are suffering from sluggish kinetics during absorption and desorption processes. Here in this work, embedding Mg particles on few-layer graphene nanosheets (FLG) via dielectric barrier discharge plasma (DBDP) assisted milling was synthesized to improve hydrogen storage properties of Mg particles. The SEM observation demonstrates that Mg particles are distributed uniformly on the surface of the graphite layer in the Mg@FLG composite. The obtained Mg-based composite (Mg@FLG) shows a hydrogen storage capacity of ～5 wt%. From the isothermal dehydrogenation kinetic curves, the composite could desorb ～4.5 wt% hydrogen within 25 min at 300 °C. Compared with pure Mg, the dehydriding kinetics of the hydrogenated Mg@FLG composite is significantly elevated, showing an activation energy of 155 J/(mol·K). In addition, the dehydrogenation peak temperature of the Mg@FLG decreases dramatically from 431 to 329 °C for MgH₂. This work implies a promising composite formation technique in Mg-based materials to enhance hydrogen storage kinetics.     

Facile preparation of binder-free NiO/MnO2-carbon felt anode to enhance electricity generation and dye wastewater degradation performances of microbial fuel cell

Binder-free NiO/MnO₂-carbon felt electrode is prepared with a facile two-step hydrothermal method. The NiO self-grown on the carbon felt is used as the skeleton structure to support the in-situ growth of MnO₂. Both the core and shell materials are excellent pseudocapacitance materials. The compositing of such pseudocapacitance metal oxides can produce synergistic effects, so that the modified electrode has a high capacitance. NiO/MnO₂-carbon felt electrode also possesses a high specific surface area, super hydrophilicity and good biocompatibility, which are conducive to the enrichment of typical exoelectrogen Geobacter. As the anode, NiO/MnO₂-carbon felt electrode can effectively improve the electricity generation and methyl orange (MO) wastewater degradation performances of microbial fuel cell (MFC). The highest output voltage and the maximum power density of MFC with NiO/MnO₂-carbon felt anode are respectively 652 mV and 628 mW m^?2, which are much higher than those of MFC with MnO₂-carbon felt anode (613 mV, 544 mW m^?2), NiO-carbon felt anode (504 mV, 197 mW m^?2) and unmodified carbon felt anode (423 mV, 162 mW m^?2). The decolourization efficiency and the chemical oxygen demand (COD) removal rate of MO for MFC with NiO/MnO₂-carbon felt anode are respectively 92.5% and 58.2% at 48 h.     

A novel high capacity,environmentally benign energy storage system: Super-iron boride battery

High electrochemical capacity of alkaline boride anodes is presented. The alkaline anodes based on transition metal borides (demonstrated with TaB, TaB₂, TiB₂ and VB₂) can deliver exceptionally high discharge capacity. Over 2000 and 3800 mAh g⁻¹ discharge capacities are obtained for the commercially available TiB₂ and VB₂ respectively, much higher than the theoretical capacity of commonly used zinc metal (820 mAh g⁻¹) alkaline anode. Coupling with the super-iron cathodes, the novel Fe⁶⁺/B²⁻ battery chemistry generates a matched electrochemical potential to the conventional MnO₂–Zn battery, but sustains a much higher electrochemical capacity. High capacity TiB₂ and VB₂ anodes are further studied by coupling with a variety of cathodes (such as MnO₂, NiOOH, KIO₄ and composite K₂FeO₄/AgO). Both TiB₂ and VB₂ show good compatibilities with each of these cathodes. With the additive AgO to the super-iron (K₂FeO₄) cathode, a K₂FeO₄/AgO composite cathode TiB₂ anode alkaline battery exhibits high-rate discharge performance.     

PdCo bimetallic nano-electrocatalyst as effective air-cathode for aqueous metal-air batteries

For wide application of metal-air batteries, the key factor is the development of catalysts for air cathodes. In the present study, PdCo/C bimetallic nanocatalysts are prepared by a facile borohydride reduction method. To improve the activity and stability, the catalysts are heat-treated at 200 °C in H₂/Ar atmosphere from 4 h to 24 h. The optimal heat-treatment time is found to be 8 h, at which the highest activity for both oxygen reduction reaction and oxygen evolution reaction is obtained. With the 8 h heat-treated PdCo/C catalyst, the rechargeable zinc-air battery exhibits a high power density of 180 mW cm^?2 and retains stability for more than 50 h at a discharge-charge current density of 10 mA cm^?2, while the magnesium-air battery obtains a power density of more than 200 mW cm^?2 and remains stable within 8 h at a discharge current density of 65 mA cm^?2.