An investigation into the effect of thickness of titanium dioxide and gold-silver nanoparticle titanium dioxide composite thin-films on photocatalytic activity and photo-induced oxygen production in a sacrificial system

Thin films of titanium dioxide and titanium dioxide with incorporated gold and silver nanoparticles were deposited onto glass microscope slides, steel and titanium foil coupons by two sol–gel dip-coating methods. The film's photocatalytic activity and ability to evolve oxygen in a sacrificial solution were assessed. It was found that photocatalytic activity increased with film thickness (from 50 to 500 nm thick samples) for the photocatalytic degradation of methylene blue in solution and resazurin redox dye in an intelligent ink dye deposited on the surface. Contrastingly, an optimum film thickness of [similar]200 nm for both composite and pure films of titanium dioxide was found for water oxidation, using persulfate (S2O82−) as a sacrificial electron acceptor. The nanoparticle composite films showed significantly higher activity in oxygen evolution studies compared with plain TiO2 films

Fabrication and characterisation of nanoscale Ni-CGO electrode from nanocomposite powders

Incorporating nanoparticles into SOC electrode is a viable method to improve the electrochemical performance. In this work, nanoparticles of NiO and gadolinia-doped ceria (CGO) approximately 10 nm in diameter fabricated using a continuous hydrothermal flow synthesis are made into nano-structured SOC fuel electrodes via mixing and co-sintering. Both the Ni and CGO are of 50-100 nm in diameter in the final electrode. FIB-SEM 3-D tomography is carried out on the nanoscale Ni-CGO electrode which has been aged for 70 h, showing a high active triple phase boundary density of 3 µm-2 and a high active double phase boundary density of 2 µm-1. The total polarisation resistance of the electrode is stable at 0.20 Ω cm2 under open circuit conditions at 800 °C annealing in humidified 5% H2-N2

Rate Response Assessment from Various Granular VRT Applicators

Variable-rate technology (VRT) adds complexity to application equipment, thereby confounding the assessment of applicator performance. The intent of this investigation was to assess the rate response of various VRT granular applicators: two spinner spreaders (A and B), and two pneumatic applicators (C and D). Variable-rate (VR) tests were conducted to quantify the rate response characteristics (delay and transition times) for the applicators. A sigmoidal function was used to model the rate response for five of the six tests. Applicator A exhibited a linear response during decreasing rate changes. Results indicated that only applicator B demonstrated consistent delay and transition times, enabling the use of a single “look-ahead” time for rate response time correction. Contouring of prescription maps increased the transition times for applicator D by enlarging the adjustment area between management zones. Rate changes were quicker for the two newer VR control systems, signifying advancement in hydraulic control valve technology. This research illustrates the need for standard testing protocols for VRT systems to help guide VRT software developers, equipment manufacturers, and end users

Quaternary ferrites by batch and continuous flow hydrothermal synthesis: a comparison

Crystalline spinel quaternary ferrites MxZn1−xFe2O4 (M = Co, Ni; x = 0.2, 0.35, 0.5, 0.65, 0.8) were synthesised through conventional batch hydrothermal synthesis (HT) at 135 °C as well as via continuous flow hydrothermal synthesis (CHFS). The as prepared compounds were thoroughly characterised from a compositional (ICP-MS, XPS) and structural (XRD) point of view in order to compare the synthetic approaches and achieve a greater understanding of how the chosen approach influences the characteristics of the resulting spinel

In situ valence modification of Pd/NiO nano-catalysts in supercritical water towards toluene oxidation

Noble metals, e.g. Pd, are often made into hybrid or composite catalysts (with less expensive materials) to oxidize industry-source emitted volatile organic compounds (VOCs) at low temperatures. In general, the loadings of these metals should be optimized to reduce costs whilst maintaining activity. There exists the possibility to obtain highly active catalysts with low loadings of noble metals by properly tuning the valence state of the metal(s). However, the relationship between the valence state and its effect on catalyst performance is still a matter of debate. In this article, we used supercritical water (sc-H2O), in the presence of oxidizing or reducing gases, as a feasible reaction medium to synthesize Pd/NiO hybrid nano-catalysts and in situ modify the valence state of Pd. After subjecting the catalysts to a range of analytical techniques, including XRD, H2-TPR, DRIFT, TPSR, etc., we unveiled that Pd0 is more active than PdOx and metal oxides in the catalytic oxidation of toluene. This is mainly because the stabilized Pd0 is capable of activating gaseous oxygen (and toluene) at low temperatures and returning to the original state by toluene even with excess oxygen. Although PdOx could desorb active oxygen under a reducing atmosphere and might assist in the oxygen spillover from NiO, it is difficult to convert into Pd0 in an oxygen-rich environment. The developed Pd0-dominated catalyst was found to be robust and highly active after an ageing test with and without water vapour

Control of crystal size tailors the electrochemical performance of alpha-V2O5 as a Mg2+ intercalation host

α-V2O5 has been extensively explored as a Mg2+ intercalation host with potential as a battery cathode, offering high theoretical capacities and potentials vs. Mg2+/Mg. However, large voltage hysteresis is observed with Mg insertion and extraction, introducing significant and unacceptable round-trip energy losses with cycling. Conventional interpretations suggest that bulk ion transport of Mg2+ within the cathode particles is the major source of this hysteresis. Herein, we demonstrate that nanosizing α-V2O5 gives a measurable reduction to voltage hysteresis on the first cycle that substantially raises energy efficiency, indicating that mechanical formatting of the α-V2O5 particles contributes to hysteresis. However, no measurable improvement in hysteresis is found in the nanosized α-V2O5 in latter cycles despite the much shorter diffusion lengths, suggesting that other factors aside from Mg transport, such as Mg transfer between the electrolyte and electrode, contribute to this hysteresis. This observation is in sharp contrast to the conventional interpretation of Mg electrochemistry. Therefore, this study uncovers critical fundamental underpinning limiting factors in Mg battery electrochemistry, and constitutes a pivotal step towards a high-voltage, high-capacity electrode material suitable for Mg batteries with high energy density