Influence of process parameters on electrochemical and physical properties of sputtered iron-doped nickel oxide thin films

The iron-doped nickel oxide films used as oxygen evolution catalysts in the photoelectrochemical production of hydrogen from solar energy were deposited by means of RF reactive magnetron sputtering from a Ni-Fe alloy target in oxygen and argon atmosphere.The effects of processing parameters on the film properties,such as overpotential,composition,surface morphology and preferred orientation,were investigated.The electrochemical experiment,structural and compositional measurements indicate that the relative lower substrate temperature,higher RF power,higher working pressure and oxygen content are necessary to gain lower overpotential.The lowest overpotential of 251 mV is obtained at a current density of 80 mA/cm2.The existence of iron,which acts as activity site,and Ni3+ ion is responsible for lowering overpotential.By analyzing SEM and XRD data,it is also noticed that an improvement in crystallinity,appropriate grain size and less crystalline phase contribute to an increased electrocatalytic activity in oxygen evolution reaction.These results mentioned above indicate that iron-doped nickel oxide is promising as an oxygen catalyst.

Lithium adsorption from brine by iron-doped titanium lithium ion sieves

Iron-doped lithium titanium oxides were prepared via a solid-state reaction and transformed into lithium ion sieves by acid treatment.Scanning electron microscopy,X-ray photoelectron spectroscopy,and transmission electron microscopy showed that Fe^3+was doped into the Ti-O lattice and Ti-Fe-O bonds were formed.Iron-doping improved lithium ion adsorption from brines.The saturated adsorption capacity of the iron-doped ion sieves in brine (Li+1.56g/L,pH =8.8)was 34.8mg/g.Lithium ion adsorption fitted pseudo-second-order kinetic and Langmuir equations,indicating that lithium ion adsorption on irondoped lithium ion sieves was chemical and predominantly monolayer.In addition,the iron-doped ion sieves showed excellent selectivity for lithium ion and good recyclability.These iron-doped ion sieves therefore provide effective lithium adsorbents for practical applications.

Light-Induced Photorefractive Waveguides in Iron-Doped Lithium Niobate Crystals

Waveguides were fabricated in lithium niobate crystals solely by light irradiation using binary optical masks and SLM-prepared optical masks. Arrayed-waveguides were also obtained by once or twice irradiations of an interferogram of two plane waves.

Introducing oxygen vacancies in TiO_(2) lattice through trivalent iron to enhance the photocatalytic removal of indoor NO

The synthesis of oxygen vacancies(OVs)-modified TiO_(2)under mild conditions is attractive.In this work,OVs were easily introduced in TiO_(2)lattice during the hydrothermal doping process of trivalent iron ions.Theoretical calculations based on a novel charge-compensation structure model were employed with experimental methods to reveal the intrinsic photocatalytic mechanism of Fe-doped TiO_(2)(Fe-TiO_(2)).The OVs formation energy in Fe-TiO_(2)(1.12 eV)was only 23.6%of that in TiO_(2)(4.74 eV),explaining why Fe^(3+)doping could introduce OVs in the TiO_(2)lattice.The calculation results also indicated that impurity states introduced by Fe^(3+)and OVs enhanced the light absorption activity of TiO_(2).Additionally,charge carrier transport was investigated through the carrier lifetime and relative mass.The carrier lifetime of Fe-TiO_(2)(4.00,4.10,and 3.34 ns for 1at%,2at%,and 3at%doping contents,respectively)was longer than that of undoped TiO_(2)(3.22 ns),indicating that Fe^(3+) and OVs could promote charge carrier separation,which can be attributed to the larger relative effective mass of electrons and holes.Herein,Fe-TiO_(2)has higher photocatalytic indoor NO removal activity compared with other photocatalysts because it has strong light absorption activity and high carrier separation efficiency.

A 2D NiFe Bimetallic Metal–Organic Frameworks for Efficient Oxygen Evolution Electrocatalysis

The oxygen evolution reaction(OER) is the cornerstone for many important energy conversion devices, including metal–air battery and water splitting.Herein, an optimized NiFe-based metal–organic framework is developed as highly efficient active material for OER. It just needs a low overpotential of 0.31 V to deliver a current density of 10 mA cm-2 with a favorable Tafel slope of 43.7 mV dec-1 in 0.1 M KOH electrolyte for the as-prepared Ni0.75Fe0.25 BDC, which is superior to RuO2. This efficient catalytic performance is due to the introduction of Fe in Ni-based MOFs could benefit the kinetics and charge transfer efficiency, resulting in the optimal activity toward OER. Besides, the obtained active material demonstrates good stability, suggesting the great potential value in sustainable electrochemical energy storage and conversion devices.

Fe-doped olivine and char for in-bed elimination of gasification tars in an air-blown fluidised bed reactor coupled with oxidative hot gas filtration

Gasification experiments were carried out in a pilot scale fluid bed reactor operated under allothermal mode and low fluidisation regime with iron-doped olivine and char as catalyst for in-situ tar abatement.The catalyst combination resulted in a reduction of 50%in the overall tar yield with respect to the reference values.Furthermore,the integration of an oxidative Hot Gas Filtration unit downstream the gasification reactor led to a further reduction in overall tar yield and relatively clean gas was obtained(approx.1 g/Nm3,benzene-free).The tar dew point of the resulting producer gas was estimated to 80℃,only 40℃ above the threshold value recommended for its valorisation in standard internal combustion engines.Moreover,catalyst elutriation and char hold-up took place to a large extent inside the reactor.The analysis of catalyst samples at different Time-On-Stream(TOS)revealed:(i)a considerable loss of iron oxides during the first hour of test because of the interparticle mechanical attrition(mostly surface abrasion)and partial reduction of hematite to magnetite and wustite but,stable composition at higher TOS,(ii)the loss of the iron oxide coverage of Fe/olivine particles and the formation of agglomerates with increasing TOS and,(iii)the amount of carbon deposited in the surface of the Fe/olivine particles increased with TOS,but in any case,these carbon deposits can be completely oxidized above 650℃.