Hierarchical nanostructured NiCo2O4 as an efficient bifunctional non-precious metal catalyst for rechargeable zinc-air batteries

A nickel-doped cobalt oxide spinel structure is a promising non-precious metal electrocatalyst for oxygen evolution and oxygen reduction in rechargeable metal-air batteries and water electrolyzers operating with alkaline electrolytes. One dimensional NiCo<inf>2</inf>O<inf>4</inf> (NCO) nanostructures were prepared by using a simple electrospinning technique with two different metal precursors (metal nitrate/PAN and metal acetylacetonate/PAN). The effect of precursor concentration on the morphologies was investigated. Single-phase, NCO with an average diameter of 100 nm, porous interconnected fibrous morphology was revealed by FESEM and FETEM analysis. The hierarchical nanostructured 1D-spinel NiCo<inf>2</inf>O<inf>4</inf> materials showed a remarkable electrocatalytic activity towards oxygen reduction and evolution in an aqueous alkaline medium. The extraordinary bi-functional catalytic activity towards both ORR and OER was observed by the low over potential (0.84 V), which is better than that of noble metal catalysts [Pt/C (1.16 V), Ru/C (1.01 V) and Ir/C (0.92 V)], making them promising cathode materials for metal-air batteries. Furthermore, the rechargeable zinc-air battery with NCO-A<inf>1</inf> as a bifunctional electrocatalyst displays high activity and stability during battery discharge, charge, and cycling processes. © The Royal Society of Chemistry.1

Hierarchical Nanostructured Pt8Ti-TiO2/C as an Efficient and Durable Anode Catalyst for Direct Methanol Fuel Cells

A catalyst for the electrochemical oxidation of methanol in direct methanol fuel cells (DMFCs) comprising Pt8Ti intermetallic nanoparticles dispersed in carbon nanorods (Pt8Ti-TiO2/C) is presented. The catalyst consists of Pt8Ti and rutile TiO2 nanoparticles dispersed in nitrogen-doped carbon hierarchical nanostructures. The Pt8Ti-TiO2/C catalyst showed a 50 mV positive onset potential and 10 times higher specific activity than a commercial Pt/C catalyst. Using a half-cell experiment, we show that Pt8Ti intermetallic nanoparticles greatly enhance the methanol oxidation activity and durability in comparison to a Pt/C commercial catalyst. More importantly, a DMFC anode constructed with Pt8Ti-TiO2/C catalyst showed 4.6 times higher power density than a commercial Pt/C catalyst at 0.35 V and 333 K. Additionally, the Pt8Ti-TiO2/C catalyst displayed superior durability in comparison to the Pt/C catalyst. Pt8Ti-TiO2/C showed an electrochemical surface area decay of 23% at the end of 3000 CV cycles, whereas the Pt/C catalyst showed a more rapid decay of 90% at the end of 3000 CV cycles. The excellent stability of the Pt8Ti-TiO2/C catalyst during the accelerated durability stability test (AST) can be attributed to the stability of the rutile TiO2 support, which is chemically resistant in the acidic electrolyte medium. The chronoamperometry and AST durability results confirmed that the Pt8Ti-TiO2/C hierarchical catalyst exhibited better stability than the pure Pt/C catalyst, suggesting that Pt8Ti-TiO2/C could be a promising anode catalyst in DMFCs. © 2015 American Chemical Society.

Porous zirconium oxide nanotube modified Nafion composite membrane for polymer electrolyte membrane fuel cells operated under dry conditions

We report a high performance and durable electrolyte membrane operated in polymer electrolyte membrane fuel cells under low relative humidity (RH). This was accomplished by incorporating water retaining mesoporous zirconium oxide (ZrO<inf>1.95</inf>) nanotubes (ZrNT) in a perfluorosulfonic acid (Nafion) membrane. Porous ZrNT with average diameters of 90nm was synthesized by pyrolysing electrospun zirconium precursor embedded polymer fibers at 600°C under an air atmosphere. The superior water retention ability and the tubular morphology of the ZrNT fillers resulted in facile water diffusion through the membrane, leading to a significant improvement in membrane proton conductivity under both fully humid and dry conditions. Compared to a commercial membrane (Nafion, NRE-212) operated under 50% and 100% RH at 80°C, the Nafion-ZrNT membrane exhibited 2.7 and 1.2 times higher power density at 0.6V, respectively. Under dry conditions (18% RH at 80°C), the Nafion-ZrNT membrane exhibited 3.1 times higher maximum power density than the NRE-212 membrane. In addition, the Nafion-ZrNT membrane also exhibited durable operation for 200h under 18% RH at 80oC. The remarkably high performance of the Nafion-ZrNT composite membrane was mainly attributed to the reduction of ohmic resistance by incorporating the mesoporous hygroscopic ZrO<inf>1.95</inf> nanotubes. © 2015 Elsevier B.V.

High performance catalyst for electrochemical hydrogen evolution reaction based on SiO2/WO3-x nanofacets

The electrochemical hydrogen evolution reaction (HER) was studied over silica/tungsten oxide nanofacets (SiO2/WO3-x) that was prepared by calcinations of electrospun polyacrylonitrile nanofibers containing silicotungstic acid under air atmosphere. It was found that the Keggin structure of precursor (H4SiW12O40.29H2O) was decomposed and transferred to crystalline monoclinic WO3 after calcinations at 500 C. The morphology of prepared catalyst after pyrolysis, observed by FE-SEM, was nanocrystals deposited on joined nanoparticles fiber. The size of nanocrystal increases with increasing annealing time. In addition, increasing annealing time also enhances interaction between SiO2 and WO3-x. The synthesized catalyst was employed as an electrocatalyst for HER. It was found that the catalyst annealed at 500 C for 5 h showed 6.6 times higher HER activity than the bulk WO3 and exhibits excellent electrochemical stability over 100 cycles. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.1

Synthesis of sulfonated poly(arylene ether ketone) block copolymers for proton exchange membrane fuel cells

Sulfonated poly(arylene ether ketone) (SPAEK) block copolymers were synthesized through nucleophilic aromatic substitution polymerization. Compared with a Nafion (NRE-212), state-of-the-art proton conducting membrane, the block copolymer membrane showed a well separated phase morphology and high proton conductivity under fully hydrated condition at 80 °C. The fuel cell operated with a SPAEK membrane showed a current density of 1617 mA cm- 2 at 0.6 V under 100% relative humidity (RH), whereas a NRE-212 membrane exhibited a current density of 1238 mA cm-2, which is about 30% lower than newly prepared SPEAK membrane. In addition, the maximum power density of 1160, and 800 mW cm-2 was observed for SPAEK, NRE-212 membranes, respectively at 80 °C under 100% RH condition. The SPEAK membrane exhibited 1.4-folds enhancement in the maximum power density in comparison with NRE-212 membrane. © 2016 Elsevier B.V.

Efficient water management of composite membranes operated in polymer electrolyte membrane fuel cells under low relative humidity

High performance and durable electrolyte membrane operated in polymer electrolyte membrane fuel cells (PEMFCs) under low relative humidity (RH) has been achieved by incorporating various diameter sizes of mesoporous hygroscopic TiO<inf>2</inf> nanotubes (TNT) in a perfluorosulfonic acid (Nafion®) membrane. Porous TNTs with different tube diameters are synthesized by thermal annealing the electrospun polymer containing titanium precursor mat at 600°C under an air atmosphere. The diameter of the TNT is significantly controlled by changing the concentration of the precursor solution. Compared to a commercial membrane (Nafion, NRE-212), the Nafion-TNT-10 composite membrane operated under 100% RH at 80°C generates about 1.3 times higher current density at 0.6V, and 3.4 times higher maximum power density operated under dry conditions (18% RH at 80°C). In addition, the Nafion-TNT-10 composite membrane also exhibits stable and durable operation under dry conditions. The remarkably high performance of the Nafion-TNT-10 composite membrane is mainly attributed to the significant reduction of the ohmic resistance as well as the improvement of cathode catalyst utilization by incorporating TNTs, which greatly enhances the water retention and the water management capability through the membrane. Furthermore, Nafion-TNT membranes exhibit superior mechanical property. © 2015 Elsevier B.V.

Facile Synthesis of Porous Metal Oxide Nanotubes and Modified Nafion Composite Membranes for Polymer Electrolyte Fuel Cells Operated under Low Relative Humidity

We describe a facile route to fabricate mesoporous metal oxide (TiO₂, CeO₂ and ZrO_1.95) nanotubes for efficient water retention and migration in a Nafion membrane operated in polymer electrolyte fuel cell under low relative humidity (RH). Porous TiO₂ nanotubes (TNT), CeO₂ nanotubes (CeNT), and ZrO_1.95 (ZrNT) were synthesized by calcining electrospun polyacrylonitrile nanofibers embedded with metal precursors. The nanofibers were prepared using a conventional single spinneret electrospinning technique under an ambient atmosphere. Their porous tubular morphology was observed by SEM and TEM analyses. HR-TEM results revealed a porous metal oxide wall composed of small particles joined together. The mesoporous structure of the samples was analyzed using BET. The tubular morphology and outstanding water absorption ability of the TNT, CeNT, and ZrNT fillers resulted in the effective enhancement of proton conductivity of Nafion composite membranes under both fully humid and dry conditions. Compared to a commercial membrane (Nafion, NRE-212) operated under 100% RH at 80 °C, the Nafion–TNT composite membrane delivered approximately 1.29 times higher current density at 0.6 V. Compared to the Nafion-TiO₂ nanoparticles membrane, the Nafion–TNT membrane also generated higher current density at 0.6 V. Additionally, compared to a NRE-212 membrane operated under 50% RH at 80 °C, the Nafion–TNT composite membrane exhibited 3.48 times higher current density at 0.6 V. Under dry conditions (18% RH at 80 °C), the Nafion–TNT, Nafion-CeNT, and Nafion-ZrNT composite membranes exhibited 3.4, 2.4, and 2.9 times higher maximum power density, respectively, than the NRE-212 membrane. The remarkably high performance of the Nafion composite membrane was mainly attributed to the reduction of ohmic resistance by the mesoporous hygroscopic metal oxide nanotubes, which can retain water and effectively enhance water diffusion through the membrane

A circular economy use of waste metalized plastic film as a reinforcing filler in recycled polypropylene packaging for injection molding applications

In the recycling point of view, the metalized plastic film is widely known to be one of the most difficult materials to be recycled due to its structural complexity. This paper investigates the effects of the ground metalized-plastic film (MF) as a filler and reinforcement in recycled polypropylene (rPP) packaging to produce a new material through circular economy. MF was incorporated to rPP from 2 to 10 wt% and it was processed by using a twin-screw extruder and an injection molding machine. For MF, elemental analysis, and x-ray diffractometer (XRD) confirmed the existence of C, O, and Al, while the differential scanning calorimetry (DSC) result evidenced the melting position of linear-low density polyethylene (LLDPE). For, rPP/MF composites, MF was found to significantly reinforce rPP with the increased tensile strength. A maximum increase of the tensile strength by around 33% was observed when MF was added at 8 wt%. Elongation at break was found to reduce with MF loading. However, there was no significant difference among rPP with 6–10 wt% MF. DSC results indicated the shifts of both crystallization and melting peaks together with the reduction of the degree of crystallinity (Xc). Based on the tensile strength, tensile elongation at break results together with the statistical analysis and waste utilization issues, the rPP with 10 wt% MF formulation was selected as a final product prototyping

Nafion-porous cerium oxide nanotubes composite membrane for polymer electrolyte fuel cells operated under dry conditions

A composite membrane operated in polymer electrolyte fuel cells (PEFCs) under low relative humidity (RH) is developed by incorporating cerium oxide nanotubes (CeNT) into a perfluorosulfonic acid (Nafion®) membrane. Porous CeNT is synthesized by direct heating a precursor impregnated polymer fibers at 500 °C under an air atmosphere. Compared to recast Nafion and commercial Nafion (NRE-212) membranes, the Nafion-CeNT composite membrane generates 1.1 times higher power density at 0.6 V, operated at 80 °C under 100% RH. Compared to Nafion-cerium oxide nanoparticles (Nafion-CeNP) membrane, the Nafion-CeNT provides 1.2 and 1.7 times higher PEFC performance at 0.6 V when operated at 80 °C under 100% and 18% RH, respectively. Additionally, the Nafion-CeNT composite membrane exhibits a good fuel cell operation under 18% RH at 80 °C. Specifically, the fluoride emission rate of Nafion-CeNT composite membrane is 20 times lower than that of the commercial NRE-212 membrane when operated under 18% RH at 80 °C for 96 h. The outstanding PEFC performance and durability operated under dry conditions is mainly attributed to the facile water diffusion capability as well as the effective hydroxyl radical scavenging property of the CeNT filler, resulting in significantly mitigating both the ohmic resistance and Nafion membrane degradation. © 2016 Elsevier B.V.

Highly Active and Durable Transition Metal-Coordinated Nitrogen Doped Carbon Electrocatalyst for Oxygen Reduction Reaction in Neutral Media

The major technical obstacles in commercialization of microbial fuel cell technology are the sluggish kinetic, high cost, and poor durability of an air cathode electrocatalyst. This research aimed to synthesize the highly active, stable and low cost non-precious metal catalyst to replace the expensive Pt electrocatalyst using a simple, low cost and scalable method. The Fe3C and Fe-N-C catalysts were prepared by direct heating the precursors under autogenic pressure conditions. X-ray diffraction pattern revealed the phase of Fe3C sample was cohenite Fe3C and graphitic carbon, while the phase of Fe-N-C catalyst was only graphitic carbon. The morphology of the synthesized catalysts was a highly porous structure with nanoparticle morphology. The surface area of the Fe3C and the Fe-N-C catalysts was 295 and 377 m2 g-1, respectively. The oxygen reduction reaction (ORR) activity of Fe-N-C catalyst was more active than Fe3C catalyst. The ORR performance of Fe-N-C catalyst exhibited about 1.6 times more superior to that of the noble Pt/C catalyst. In addition, the Fe-N-C catalyst was durable to operate under neutral media. Thus, a novel autogenic pressure technique was a promising method to effectively prepare an highly active and durable non-precious metal catalyst to replace the precious Pt/C catalyst