Spontaneous selective deposition of iron oxide nanoparticles on graphite as model catalysts

Nanostructure fabrication by area selective deposition: a brief review

In recent years, area-selective deposition (ASD) processes have attracted increasing interest in both academia and industry due to their bottom-up nature, which can simplify current fabrication processes with improved process accuracy. Hence, more research is being conducted to both expand the toolbox of ASD processes to fabricate nanostructured materials and to understand the underlying mechanisms that impact selectivity. This article provides an overview of current developments in ASD processes, beginning with an introduction to various approaches to achieve ASD and the factors that affect selectivity between growth and non-growth surfaces, using area-selective atomic layer deposition (AS-ALD) as the main model system. Following that, we discuss several other selective deposition processes, including area-selective chemical vapor deposition, area-selective sputter deposition, and area-selective molecular beam epitaxy. Finally, we provide some examples of current applications of ASD processes and discuss the primary challenges in this field.

Multilayered LDH/Microcapsule Smart Epoxy Coating for Corrosion Protection

A multilayered smart epoxy coating for corrosion prevention of carbon steel was developed and characterized. Toward this direction, as a first step, zinc-aluminum nitrate-layered double hydroxide (Zn/Al LDH) was synthesized using the hydrothermal crystallization technique and then loaded with dodecylamine (DOD), which was used as an inhibitor (pH-sensitive). Similarly, the synthesis of the urea-formaldehyde microcapsules (UFMCs) has been carried out using the in-situ polymerization method, and then the microcapsules (LAUFCs) were encapsulated with linalyl acetate (LA) as a self-healing agent. Finally, the loaded Zn/Al LDH (3 wt %) and modified LAUFCs (5 wt %) were reinforced into an epoxy matrix to develop a double-layer coating (DL-EP). For an exact comparison, pre-layer epoxy coatings comprising 3 wt % of the loaded Zn/Al LDH (referred to as LDH-EP), top-layer epoxy coatings comprising 5 wt % linalyl acetate urea-formaldehyde microcapsules (referred to as UFMLA COAT), and a blank epoxy coating (reference coating) were also developed. The developed epoxy coatings were characterized using various techniques such as XRD, XPS, BET, TGA, FTIR, EIS, etc. Electrochemical tests performed on the synthesized coatings indicate that the DL-EP demonstrates improved self-healing properties compared to LDH-EP and UFMLA COAT.

Synthesis and Characterization of Nanocrystalline Boron-Nitride Thin Films by Ion Milling and Thermal Treatment for Tribological Coatings: An Approach to Quantifying the Growth Dynamic Process

Hexagonal boron-nitride nanoparticle coating was deposited on AISI 1045 steel surface. The deposition process included a transformation of B-containing thin organic film into nanocrystalline BN using two methods: thermal annealing at 450-850 °C and reactive ion etching in Ar/N2 plasma. The film structure, phases, and film morphology of deposited nanoparticles of boron nitride on AISI 1045 steel were characterized by XPS, XRD, and EDS. Post-annealing at 450 °C does not lead to the formation of a BN phase in the layer. A non-stoichiometric BN phase with nitrogen deficiency appears at 650 °C. At 850 °C annealing, the formed BN phase is completely stoichiometric. The effects of deposited and incorporated BN on the friction and hardness properties of AISI 1045 steel were also studied. The post-annealing process improved the hardness from 5.35 to 11.4 GPa, showing a pronounced linear temperature dependence. An original approach was adopted to quantify the energy-dependent growth constants based on the indentation load-discharge curves measured on samples treated under different conditions. Those constants describe the rate of the reactions and the type of interdiffusion process characteristic for each material used. This approach can partially fulfill the role of the Rutherford backscattering spectrometry profile, which is an expensive and time-consuming process, mainly when light elements such as boron and nitrogen are used.

Bifunctional PDDA-stabilized β-Fe2O3 nanoclusters for improved photoelectrocatalytic and magnetic field enhanced photocatalytic applications

Bifunctional β-Fe2O3@PDDA nanoclusters applied for the efficient photoelectrocatalytic oxygen evolution reaction and magnetic field enhanced photocatalytic degradation of pollutants.

Core-Shell Fe2O3@La1-xSrxFeO3-δ Material for Catalytic Oxidations: Coverage of Iron Oxide Core, Oxygen Storage Capacity and Reactivity of Surface Oxygens

A series of Fe2O3@LSF (La0.8Sr0.2FeO3-δ perovskite) core-shell materials (CSM) was prepared by infiltration of LSF precursors gel containing various complexants and their mixtures to nanocrystalline aggregates of hematite followed by thermal treatment. The content of LSF phase and amount of carboxyl groups in complexant determine the percent coverage of iron oxide core with the LSF shell. The most conformal coating core-shell material was prepared with citric acid as the complexant, contained 60 wt% LSF with 98% core coverage. The morphology of the CSM was studied by HRTEM-EELS combined with SEM-FIB for particles cross-sections. The reactivity of surface oxygen species and their amounts were determined by H2-TPR, TGA-DTG, the oxidation state of surface oxygen ions by XPS. It was found that at complete core coverage with perovskite shell, the distribution of surface oxygen species according to redox reactivity in CSM resemble pure LSF, but its lattice oxygen storage capacity is 2-2.5 times higher. At partial coverage, the distribution of surface oxygen species according to redox reactivity resembles that in iron oxide.

Simultaneous enhancement of treatment performance and energy recovery using pyrite as anodic filling material in constructed wetland coupled with microbial fuel cells

Constructed wetland coupled with microbial fuel cells (CW-MFCs) are a promising technology for sustainable wastewater treatment. However, the performance of CW-MFCs has long been constrained by the limited size of its anode. In this study, we developed an alternative CW-MFC configuration that uses inexpensive natural conductive pyrite as an anodic filling material (PyAno) to extend the electroactive scope of the anode. As a result, the PyAno configuration significantly facilitated the removal of chemical oxygen demand, ammonium nitrogen, total nitrogen, and total phosphorus. Meanwhile, the PyAno increased the maximum power density by 52.7% as compared to that of the quartz sand control. Further, a typical exoelectrogen Geobacter was found enriched in the anodic zone of PyAno, indicating that the electroactive scope was extended by conductive pyrite. In addition, a substantial electron donating potential was observed for the anodic filling material of PyAno, which explained the higher electricity output. Meanwhile, a higher dissimilatory iron reducing potential was observed for the anodic sediment of PyAno, demonstrating the integrity of an iron redox cycling in the system and its promotive effect for the wastewater treatment. Together, these results implied that the PyAno CW-MFCs can be a competitive technology to enhance wastewater treatment and energy recovery simultaneously.

Insights of the formation mechanism of nanostructured titanium oxide polymorphs from different macromolecular metal-complex precursors

The insight into the mechanism of the unprecedented formation of pure anatase TiO2 from the macromolecular (Chitosan)•(TiOSO4)n precursor has been investigated using micro Raman spectroscopy, Scanning Electron Microscopy (SEM) and thermogravimetric/differential thermal analysis (TGA/DTA). The formation of a graphitic film was observed upon annealing of the macromolecular precursor, reaching a maximum at about 500 °C due to decomposition of the polymeric chain of the Chitosan and (PS-co-4-PVP) polymers. The proposed mechanism is the nucleation and growth of TiO2 nanoparticles over this graphitic substrate. SEM and Raman measurements confirm the formation of TiO2 anatase around 400 °C. The observation of an exothermic peak around 260 °C in the TGA/DTA measurements confirms the decomposition of carbon chains to form graphite. Another exothermic peak around 560 °C corresponds to the loss of additional carbonaceous residues.

Novel Bifunctional Separator with a Self-Assembled FeOOH/Coated g-C3N4/KB Bilayer in Lithium-Sulfur Batteries

Separator modification with metal oxide and carbon composite recently has become a potential and competitive way to confine polysulfide diffusion and mitigate the shuttling effect. However, other modification methods also have an impact on the stability of the modified layer and the enhancement of electrochemical performance. Herein, we first design a novel bifunctional separator combined with one self-assembled FeOOH layer via a chemical way and one conductive g-C₃N₄/KB layer by physical coating. Different from directly coating the metal oxide and carbon composite on the separator, the self-assembled FeOOH layer is firmly formed on the PP separator, which enables the chemical capture of the soluble polysulfide and prohibit the shuttling effect. Then, the coated g-C₃N₄/KB layer is further introduced to greatly enhance the transportation of lithium ions and physically confine the migration of intermediates. As a result, the battery with this bifunctional separator (G-SFO) achieves outstanding rate capacities (1000, 901, and 802 mA h/g at 0.5, 1, and 2 C). After 900 cycles at 1 C, it also shows excellent long cycle performance, with relatively low fading (0.055%). This original fabrication will present a new and feasible strategy for fabricating a bifunctional separator with metal oxide and carbon material.