Abuliti Abudula

Nanostructured catalysts for electrochemical water splitting: current state and prospects

Hydrogen is an ideal candidate for the replacement of fossil fuels in the future due to zero emission of carbonaceous species during its utilization. Water electrolysis is a dependable link of primary renewable energy and stable hydrogen energy. In this work, the fundamentals of water electrolysis, current popular electrocatalysts developed for cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER) in liquid electrolyte water electrolysis are reviewed. The main HER catalysts include noble metals, non-noble metals and composites, noble metal-free alloys, metal carbides, chalcogenides, phosphides and metal-free materials while the OER catalysts are focused on efficient Co-based, Ni-based materials and layered double hydroxide (LDH) materials. The strategies to improve catalytic activity, long-term durability and endurance to electrochemical erosion are introduced. The main challenges and future prospects for the further development of electrodes for water electrolysis are discussed. It is expected to give guidance for the development of novel low-cost nanostructured electrocatalysts for electrochemical water splitting.

Facile preparation of ion-imprinted composite film for selective electrochemical removal of nickel(II) ions.

A facile unipolar pulse electropolymerization (UPEP) technique is successfully applied for the preparation of ion-imprinted composite film composed of ferricyanide-embedded conductive polypyrrole (FCN/PPy) for the selective electrochemical removal of heavy metal ions from wastewater. The imprinted heavy metal ions are found to be easily removed in situ from the growing film only by tactfully applying potential oscillation due to the unstable coordination of FCN to the imprinted ions. The obtained Ni(2+) ion-imprinted FCN/PPy composite film shows fast uptake/release ability for the removal of Ni(2+) ions from aqueous solution, and the adsorption equilibrium time is less than 50 s. The ion exchange capacity reaches 1.298 mmol g(-1) and retains 93.5% of its initial value even after 1000 uptake/release cycles. Separation factors of 6.3, 5.6, and 6.2 for Ni(2+)/Ca(2+), Ni(2+)/K(+), and Ni(2+)/Na(+), respectively, are obtained. These characteristics are attributed to the high identification capability of the ion-imprinted composite film for the target ions and the dual driving forces resulting from both PPy and FCN during the redox process. It is expected that the present method can be used for simple preparation of other ion-imprinted composite films for the separation and recovery of target heavy metal ions as well.

Selective catalytic conversion of bio-oil over high-silica zeolites.

Four high silica zeolites, i.e., HSZ-385, 890, 960, and 990 were utilized for the selective catalytic conversion of bio-oil from Fallopia japonica to certain chemicals in a fixed-bed reactor. The Beta-type HSZ-960 zeolite showed the highest selectivity to hydrocarbons, especially to aromatics as well as PAH compounds with the lowest unwanted chemicals while HSZ-890 showed high selectivity to aromatics. NH3-Temperature Programmed Desorption (TPD) analysis indicated that different amounts of acid sites in different zeolites determined the catalytic activity for the oxygen removal from bio-oil, in which the acid sites at low temperature (LT) region gave more contribution within the utilized temperature region. The reusability test of HSZ-960 showed the stability of hydrocarbons yield at higher temperature due to the significant contribution of coke gasification which assisted further deoxygenation of bio-oil. These results provide a guidance to select suitable zeolite catalysts for the upgrading of bio-oil in a practical process.

Highly-efficient steam reforming of methanol over copper modified molybdenum carbide

Cu doped molybdenum carbide (Cu–MoxCy) catalysts were prepared by carburization of Cu doped molybdenum oxide (Cu–MoO3) using a temperature-programmed reaction with a 20% CH4–H2 mixture at 700 °C. Phase transition of the prepared molybdenum carbide was found to be related to the doping amount of Cu: with the increase in the doping amount of Cu/Mo molar ratio of 1.6/98.4 to 10/90, the cubic α-MoC1−x phase increased in the catalyst, but with the continued increase of the doping amount to a Cu/Mo molar ratio of 15/85, the α-MoC1−x phase began to decrease, and when the Cu doping amount reached a Cu/Mo molar ratio of 25/75, the α-MoC1−x phase became very weak and mainly hexagonal β-Mo2C phase was found in the catalysts. TEM images indicated that carbon growth on the surface of Cu occurred during the carburization process in the case of high Cu doping. Steam reforming of methanol (SRM) over the Cu–MoxCy catalyst was investigated at a temperature range of 200–400 °C. It is found that Cu–MoxCy catalyst with Cu/Mo molar ratios in the range of 1.6/98.4–10/90 showed high catalytic activity as well as long-term stability. X-ray photoelectron spectroscopy analysis indicated the coexistence of CuI and CuII species on the surface of the molybdenum carbide. The existence of CuI could result in high activity for methanol conversion and high stability, which might result from the strong interaction between Cu and Mo2C support.

An intelligent displacement pumping film system: a new concept for enhancing heavy metal ion removal efficiency from liquid waste.

A concept of electrochemically switched ion exchange (ESIX) hybrid film system with piston-like proton pumping effect for the removal of heavy metal ions was proposed. Based on this concept, a novel ESIX hybrid film composed of layered alpha zirconium phosphate (α-Zr(HPO4)2; α-ZrP) nanosheets intercalated with a potential-responsive conducting polyaniline (PANI) was developed for the removal of Ni(2+) ions from wastewater. It is expected that the space between α-ZrP nanosheets acts as the reservoir for the functional ions while the intercalated PANI works as the potential-sensitive function element for piston-like proton pumping in such ESIX hybrid films. The prepared ESIX hybrid film showed an excellent property of rapid removal of Ni(2+) ions from wastewater with a high selectivity. The used film was simply regenerated by only altering the applied potential. The ion pumping effect for the ESIX of Ni(2+) ions using this kind of film was proved via XPS analysis. The proposed ESIX hybrid film should have high potential for the removal of Ni(2+) ions and/or other heavy metal ions from wastewater in various industrial processes.

Steam reforming of tar derived from lignin over pompom-like potassium-promoted iron-based catalysts formed on calcined scallop shell

In order to understand the improvement effect of potassium (K) on the catalytic activity of iron-loaded calcined scallop shell (CS) for the steam reforming tar derived from biomass, various K precursors were applied for the catalyst preparation. It is found that pompom-like iron-based particles with a mesoporous structure were easily formed on the surface of calcined scallop shell (CS) when K2CO3 was used as K precursor while no such kind of microsphere was formed when other kinds of K precursors such as KOH and KNO3 were applied. The optimum K-loading amount for the preparation of this catalyst was investigated. Based on the experimental results obtained, a mechanism for the formation of these microspheres was proposed. This pompom-like potassium-promoted iron-based catalyst showed a better catalytic activity and reusability for the steam reforming of tar derived from lignin.

Homogeneous nanosheet Co3O4 film prepared by novel unipolar pulse electro-deposition method for electrochemical water splitting

A unipolar pulse electro-deposition (UPED) method is used to prepare nanosheet Co3O4 film on a carbon rod substrate in aqueous solution and compared with other conventional methods, i.e., the cyclic voltammetry (CV) method, potentiostatic method (PM) and pulse potentiostatic method (PPM). Co3O4 films prepared by the UPED method show a more uniform structure on carbon rod and higher catalytic activity than those by other methods, and oxygen evolution reaction over it with an overpotential of 275 ± 2.3 mV results in a current density of 10 mA cm−2 in 1.0 mol L−1 KOH. Such an excellent performance should be attributed to its highly porous nanosheet structure with honeycomb-like morphology.

Cobalt hydroxide [Co(OH)2] loaded carbon fiber flexible electrode for high performance supercapacitor

Cobalt hydroxide nanoflakes are uniformly loaded on flexible carbon fiber (CF) paper, and provide good electrical connectivity to the current collector for use as supercapacitors. The unique porous nanostructure offers low ion diffusion and charge transfer resistance in the electrode. The effect of loading mass on electrochemical properties is investigated. The electrode with a mass loading of 2.5 mg cm−2 shows the maximum specific capacitance of 386.5 F g−1 at a current density of 1 mA cm−2. Also the same electrode provides a good rate capability with energy and power densities of 133.5 W h kg−1 and 1769 W kg−1, respectively even at a higher current density of 10 mA cm−2. The electrode reveals a cyclic stability of 92% over 2000 cycles. This kind of flexible, lightweight electrode could be effectively utilized for flexible supercapacitor fabrication, especially for wearable electronics.

Prospects of oxide ionic conductivity bismuth vanadate-based solid electrolytes

Abstract The benefits of lowering the operation temperature of solid oxide fuel cells (SOFCs) have attracted great attention worldwide. There has been an enormous effort in the literature for the improvement of the electrolyte materials working at lower temperatures. The family of BiMeVOx (Bi–bismuth, Me–dopant metal, V–vanadium, Ox–oxide) materials has been found to have specific properties as oxide ion conductor (electrolyte) for low operation temperature. These materials exhibit uniquely structural features rather different from those of other solid electrolytes. It is possible to use these as the electrolyte in SOFCs. This article attempts to review the main structural and electrochemical characteristics of BiMeVOx materials in order to show a guideline for designing novel BiMeVOx-based electrolyte for low-temperature SOFCs. The prospects and challenges for the application of these materials as the electrolyte are discussed.

Mg-modified ultra-stable Y type zeolite for the rapid catalytic co-pyrolysis of low-rank coal and biomass

To improve the quality of oil derived from the fast co-pyrolysis of low-rank coal with biomass, various metal-modified ultra-stable Y type (USY) zeolites are mixed with the samples for the co-pyrolysis process. It is found that Mg-modified USY zeolite shows high catalytic activity with high coking resistance ability in this study. A further treatment of Mg-modified USY zeolite by steaming process further improves the coke resistance and the catalytic activity toward production of more hydrocarbons in the pyrolytic oil. It is indicated that Al atoms in the original zeolite framework could be dislocated by the steam treatment and a new framework consisting of Al–Mg–Si could be formed on the outside of the zeolite framework, which is beneficial to change the physical and chemical properties of the zeolite and increase the catalytic activity and coke resistance ability in the process of rapid catalytic co-pyrolysis of low rank coal with biomass.