Basic Metal Oxides Research Articles

Combustion of volatile organic compounds in a domestic microwave oven using regenerable sorbent-catalyst combinations

Volatile Organic Compounds (VOCs) traps that could easily be regenerated while simultaneously destroying the desorbed VOCs would represent a major breakthrough. A domestic microwave (MW) oven was used here at a power of 800 W to regenerate sorbents loaded with toluene, n-decane or formaldehyde and then combust the released VOCs on a MW-absorbing catalyst. Porous polymer Tenax and various zeolites were tested as sorbents and base metal oxides were employed as combustion catalysts. The locations of the sorbent and catalyst beds were chosen to allow for a strong MW absorption by the catalysts, some of which glowed red within 3 s after turning on the MW, allowing essentially full combustion (above 98 % conversion) of the VOCs to CO2 and H2O. Water (0.6 vol%) neither affected the sorption of toluene and n-decane in Tenax and that of formaldehyde in silicalite-1 nor the combustion of these VOCS over a La-Ce-Mn-O catalyst.

The effect of acidic–basic structural modification of nickel-based catalyst for ammonia decomposition for hydrogen generation

The utilization of non-precious nickel-based catalyst in increasing ammonia dissociation for COx-free hydrogen production was investigated. Typically, Co, La and basic metal oxides (Na, K, Ba) promoters were synthesized with nickel over acidic gamma alumina support. The main objective of the study was to modify the acid-base surface of catalyst structure thereby increasing ammonia dissociation activity. The catalytic activity for ammonia decomposition was strongly influenced by the addition of Na and K oxide promoters over 15 %Ni/Al2O3 resulting in moderate-stronger basic sites suitable for ammonia conversion. The addition of Na and K oxides showed a clear trend in tuning the trimetallic catalyst and significantly reducing the amount of strongly adsorbed hydrogen on the catalyst surface. This results in higher ammonia conversion which increased as a function of temperature to 32.4 %, 67.5 % and 95.3 % at 430 ᵒC, 485 ᵒC, and 533 ᵒC, respectively. Ammonia conversion using promoters was stable with no degradation of performance and the conversion increased with the decrease in WHSV. The catalytic reactivity over trimetallic catalysts was systematically influenced by their basic-acidic property that promoted ammonia dehydrogenation on the surface of nickel oxide-based catalyst.

Facile synthesis of CuAl2O4/rGO nanocomposite via the hydrothermal method for supercapacitor applications

Transition metal-based spinel oxides are fascinating supercapacitor electrodes materials due to their good specific capacitance (Cs) and cost-effectiveness. But the spinel materials show poor cycling stability due to their limited surface area. This issue was reduced by using carbon-based electrode materials such as rGO, which enhances the electroactive surface area that leads to improve the number of reactive sites. In this research, a simple hydrothermal approach was utilised to synthesise the CuAl2O4/rGO (CAO/rGO) nanocomposite. It successively characterised with different analytical techniques to study the physiochemical property of the synthesized materials. Additionally, the potential of the materials as the electrode was determined with a three-electrode configuration by utilising different electrochemical tools that were performed to assess the characteristics of the electrode material. The synthesised nanocomposite exhibits a magnificent specific capacitance (Cs) of 1206.14 F/g at 1 A/g, while demonstrating specific energy (Ed) of 34.83 Wh kg−1 and specific power (Pd) of 228 W kg−1 which is higher than individuals and also shows high retention capacitance value of 93.36% after 8000th charge/discharge (GCD) cycles. The symmetric behaviour of the fabricated electrode is also determined with two electrode systems exhibiting the specific energy and specific capacitance of 16.54 Wh kg−1 and 601.91 F/g, correspondingly. This study demonstrates that incorporating rGO into CuAl2O4 nanoarray improves energy storage performance and it has the potential to work in other energy storage devices.

Investigation on Mechanical and Machinability Properties of Aluminium Metal Matrix Composite Reinforced with Titanium Oxide (TiO2) and Graphite (Gr) Particles

This research paper deals with the preparation process and testing of metal matrix composites comprising Aluminium alloy (Al 6061) as the base metal and Titanium oxide (TiO2) and Graphite (Gr) as reinforcements. Due to their high specific strength, superior malleability, lightweight, stiffness and excellent resistance to corrosion, oxidation and wear, the aluminium metal matrix composites are preferred in the automobile and industrial sectors for component manufacturing. No work reported on machinability properties of Titanium oxide (TiO2) and Graphite (Gr) reinforced aluminium composites so far. This study prepared and studied samples composed of variable proportions of titanium oxide and graphite. The samples were prepared using the stir casting method. While stirring, the required additives were added to the molten aluminium mixture. To perform the tests, the samples were prepared according to standard dimensions after solidification. The mechanical properties of the prepared composite were examined using various test procedures, such as strength and hardness. Scanning electron microscopy was used to examine the microstructure of the test composite samples. The EDAX test confirmed the presence of graphite and Titanium oxide in the aluminium based composite specimens. Furthermore, machining was done to study the cutting forces on the tool. The test results showed a significant impact of the reinforced materials on the mechanical and machinability properties of aluminium metal matrix composites. Gr decreases hardness, while TiO2 increases it. TiO2 and Gr reinforcements increase the tensile strength of Al 6061 composites. The addition of TiO2 decreased the composite's elongation. The proof strength of 2 % Al6061 was high, however it decreased with 3 % Gr and increased with TiO2 reinforcement. Reinforcements increase cutting forces during machining; when comparing the machining of Al 6061 to that of 3 % Gr and 5 % TiO2, a 50 % increase in cutting forces is noticed. However, excessive reinforcements may reduce cutting forces due to poor matrix-reinforcement adhesion. HIGHLIGHTS The mechanical and machinability properties of aluminium metal metrics reinforced with Titanium oxide (TiO2) and graphite (Gr) have not been reported so far in the literature. In this study, aluminium based composites reinforced with variable proportions of titanium oxide and graphite were prepared and studied. The fabrication process was done by stir casting by adding the required additives into the molten mixture of aluminium, followed by continuous stirring. The solidified samples were cut according to the standard dimensions and various test procedures were conducted to examine the mechanical and machinability properties of the prepared composites. Gr reduces hardness, whereas TiO2 enhances it. TiO2 and Gr reinforcements boost Al 6061 composite tensile strength. TiO2 addition reduced elongation of the composite. 2 % proof strength of Al 6061 was strong, however it dropped with 3 % Gr and rose with TiO2 reinforcement. Reinforcements results higher cutting forces while machining, however excessive supplements lower cutting forces may be due to poor matrix-reinforcement bonding. GRAPHICAL ABSTRACT

Preparation of rich hydrocarbon biofuels from cracking of waste cooking oil by CaO@Zn-KIT-6

The preparation of biofuel from bio-oils is of great importance to the development of renewable energy and to alleviate environmental pollution problems. In this work, acidic mesoporous silica Me-KIT-6 (Me = Zn, Al, Zr, Sn, Mn) were prepared and coated with basic metal oxides, and the CaO@Me-KIT-6 catalyst was obtained, and tested in the catalytic cracking reaction of waste oils and fats. The structure of the catalyst was characterized by X-ray diffraction, N2 physical adsorption and transmission electron microscopy (TEM), the acidity/basicity was characterized by chemisorption (NH3-TPD/CO2-TPD), and the structure-performance relationship in waste cooking oil catalytic cracking was investigated in detail. The results showed that CaO@Zn-KIT-6 catalyst had a good catalytic performance with a liquid biofuel yield of 66.30% and an acid value of about 23.35 mg KOH/g. The carbon distribution of the liquid biofuel concentrated in the range of C13-C18 with 67.80% of hydrocarbon products. The synthesized core-shell catalysts displayed multifunctional role resulting from tailored acid-base synergy.

The production of debrominated aromatics via the catalytic pyrolysis of flexible printed circuit boards

Pyrolysis is an environmental technology for the proper treatment of electronic waste (e-waste) for the production of fuel. However, the presence of brominated compounds in pyrolysis oil makes its commercialization difficult. In this study, various types of zeolites, HY (30), HZSM-5 (30), HZSM-5 (50), HZSM-5 (280), and basic metal oxides (MgO and CaO) were used for the pyrolysis of flexible printed circuit boards (FPCBs) for the first time to produce bromine-free oil. A higher production efficiency of debrominated aromatic hydrocarbons, primarily benzene, toluene, ethylbenzene, xylenes (BTEXs), and naphthalene with zeolites, was achieved over basic metal oxides. The use of HZSM-5 (HZ) (30) increased the amount of benzene (an area of 31.5 × 107) and toluene (an area of 17.6 × 107), and a high debromination efficiency was observed for basic metal oxides owing to the strong affinity of halides toward the Ca2+ and Mg2+ ions. Among the BTEXs, benzene (an area of 31.5 × 107) and toluene (an area of 17.6 × 107) were obtained as highly selective monoaromatics in the presence of the catalyst HZ (30). CaO and HZ (30) were effective for debromination and aromatic production, respectively. The in-situ CaO/ex-situ HZ (30) combination revealed ∼ 100% debromination efficiency; however, the total aromatic hydrocarbon production was higher on the in-situ HZ (30)/ex-situ CaO with ∼ 77.5% debromination efficiency. Meanwhile, the in-situ HZ (30)/ex-situ CaO configuration could achieve ∼ 100% debromination efficiency by increasing the amount of CaO to 7 times to feed.

Influence of Calcination Temperature on Electrochemical Properties of Perovskite Oxide Nanofiber Catalysts

Energy conversion and storage systems have recently attracted significant attention owing to increasing environmental and energy problems. However, the slow kinetics of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) render their commercialization difficult. Many studies are being conducted to replace precious metal catalysts that have high activity for the ORR and OER but have scarcity and low stability. In this study, Sm0.5Sr0.5CoO3 (SSC) nanofibers were fabricated via the electrospinning of non-precious metal-based perovskite oxides to replace precious metal catalysts. In addition, the properties and electrochemical performance of SSC fibers synthesized at different calcination temperatures were evaluated. The small crystallite size, high specific surface area, abundant oxygen vacancies, and high ORR/OER activity suggest that SSC800 hollow fibers are optimal bifunctional catalysts.

High-performance metal-base bifunctional catalysts (NixMgy-MMO) for aqueous phase reforming of methanol to hydrogen

Reforming methanol in an aqueous phase is of great interest, including the water–gas shift (WGS) reaction for converting the CO formed from the dehydrogenation of methanol (DM) to CO2 and promoting hydrogen gas production by 50%. Ni-based catalysts are highly active for catalyzing the involved dehydrogenation reaction but perform poorly at the low temperature range for the WGS reaction. In this work, metallic Ni-catalytic sites supported on basic mixed metal oxides (NixMgy-MMO), prepared from NiMgAl layered double hydroxide (LDH) precursors, were applied for the first time in the aqueous phase reforming of methanol (APRM). The Ni3Mg1-MMO catalyst demonstrated outstanding catalytic performance with a high hydrogen production rate of 167.2 μmolH2/gcat./s and a low CO selectivity of 1.9% at the temperature of 240 °C. These are among the best literature results for the APRM catalyzed by Ni-based catalysts. Compared to the neutral Ni@NC catalyst, the metal-base bifunctional Ni3Mg1-MMO catalyst significantly boosts the WGS process, reducing the CO selectivity and enhancing the APRM. The structure-performance studies of the NixMgy-MMO catalysts in the reactions of DM, WGS, and APRM showed that the intrinsic activity for DM increases significantly as the Ni particle size decreases, while WGS and APRM reactions are dominantly improved by the medium basic property that originated from Mg-O pairs. As a result, the intrinsic activity of the catalysts in APRM also decreases as the Ni particle size increases. These new findings are transferable to the design of efficient metal-base bifunctional catalysts for reactions similar to WGS and APRM.

Recent progress in green synthesized transition metal-based oxides in lithium-ion batteries as energy storage devices

Transition metal-based oxide nanoparticles have been greatly employed in many areas relevant to mankind and can be synthesized through various routes such as chemical, physical, and green synthesis methods. Research on green synthesized transition metal-based oxide materials with structure at nanometer scale has gained considerable attention over decades due to the synergy effects between the metal ion and phyto-constituents in the green element source. Researchers have reported that nanoparticles produced through green synthesis have glaring advantages such as fewer toxic impurities, environmentally benign, low-cost thrifty, high-rate performance, better stability, ability to control the particle's shape and size, amongst others when compared to others synthesized via conventional approaches. Consequent upon that, serious attentions is currently being deployed in the green chemistry education as the better alternative to achieve a sustainable and transformative innovative synthesis technique. This review highlights a brief outlook of green synthesis using leaf extract as a reducing/oxidizing agent, electrochemical properties of transition metal-based oxide nanoparticles synthesized via green synthesis. By focusing on green synthesis method using leaf extract, the hope is that such transformative innovative technique will enhance the production of high-rate performance transition metal-based oxide electrode for LIB and other high energy storage devices applications. This will drastically reduce the use of synthetic chemicals that pollutes environment.

Basic metal oxide integrated DBD packed bed reactor for the decomposition of CO2

A coaxial dielectric barrier discharge (DBD) reactor was used to perform catalytic non-thermal plasma for CO2 conversion under ambient conditions. A systematic study was made to understand the role of basic oxides in activating weakly acidic CO2. For this purpose, MO/γ-Al2O3 (M = Mg, Ca, Sr, and Ba) catalysts were synthesized and integrated with the DBD reactor. The applied voltage was varied from 16 kV to 22 kV to determine the effect of applied voltage on CO2 conversion. Plasma discharge generates high-energy electrons that activate the basic oxides. Integration of basic metal oxides with the non-thermal plasma reactor resulted in a higher CO2 conversion. The adsorption of weakly acidic CO2 on the basic sites is responsible for the higher conversion of catalytic plasma reactor over plasma reactor alone. Among the basic metal oxides studied, SrO loaded γ-Al2O3 resulted in the best conversion, where CO2 conversion of ∼ 12% and energy efficiency of ∼ 1.46 mmol kJ−1 was attained at a power of 1.8 W. The concentration of O2 and O3 was measured during the reaction. The hybridized system's superior performance may be due to increased charge deposition and altered gas-phase chemistry because of catalyst integration. BOLSIG + software was used to compute the mean electron energies and electron energy distribution function for various packing conditions.

Thermodynamics of Silicon Nanowire Growth under Unintended Oxidation of Catalytic Particles

In this paper, we focus on the thermodynamics of redox reactions occurring during the vapor-liquid-solid (VLS) growth of silicon nanowires (NWs) with the participation of liquid solutions of metal catalysts. The growth of NWs is difficult with the participation of Ti, Al, and Mg particles; this is because in this case, the drops of the metal catalyst are strongly oxidized and crystals either do not form at all or are characterized by instability in the direction of growth. However, the particles of Cu, Ni, and Fe give a much more stable growth of NWs. We have also established that if the oxide film of catalytic particles is formed by the basic metal oxides, then the silicon-NWs' growth slows down. In this work, we have concluded that only metals with a lower chemical affinity for O2 than Si are applicable as catalysts for the NWs' growth.

Hybrid Plasma-Catalytic CO2 Dissociation over Basic Metal Oxides Combined with CeO2

The problem of CO2 waste in the atmosphere is a major concern, and methods of CO2 utilization are being currently developed. In the present work, a plasma-catalytic process is applied for CO2 dissociation. A series of MgO and CeO2-containing catalysts were synthesized, and the samples were characterized by: a low-temperature N2 adsorption-desorption analysis, X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed desorption of CO2, and X-ray fluorescence spectroscopy. It was stated that under dielectric barrier discharge conditions, the catalyst surface, composition, and phase content remain unchanged. The superior catalytic activity of the MgCe-Al sample is attributed to the combination of weak basic sites and oxygen vacancies on the catalyst surface.

Graphene-anchored Ni6MnO8 nanoparticles with steady catalytic action to accelerate the hydrogen storage kinetics of MgH2

Transition metal-based oxides have been proven to have a substantial catalytic influence on boosting the hydrogen sorption performance of MgH2. Herein, the catalytic action of Ni6MnO8@rGO nanocomposite in accelerating the hydrogen sorption properties of MgH2 was investigated. The MgH2 + 5 wt% Ni6MnO8@rGO composites began delivering H2 at 218 °C, with about 2.7 wt%, 5.4 wt%, and 6.6 wt% H2 released within 10 min at 265 °C, 275 °C, and 300 °C, respectively. For isothermal hydrogenation at 75 °C and 100 °C, the dehydrogenated MgH2 + 5 wt% Ni6MnO8@rGO sample could absorb 1.0 wt% and 3.3 wt% H2 in 30 min, respectively. Moreover, as compared to addition-free MgH2, the de/rehydrogenation activation energies for doped MgH2 composites were lowered to 115 ± 11 kJ/mol and 38 ± 7 kJ/mol, and remarkable cyclic stability was reported after 20 cycles. Microstructure analysis revealed that the in-situ formed Mg2Ni/Mg2NiH4, Mn, MnO2, and reduced graphene oxide synergically enhanced the hydrogen de/absorption properties of the Mg/MgH2 system.

Electrocatalysis of Selective Chlorine Evolution Reaction: Fundamental Understanding and Catalyst Design

<p>The electrochemical chlorine evolution reaction (CER) is an important electrochemical reaction and has been widely used in chlor–alkali electrolysis, on-site generation of ClO<sup>−</sup>, and Cl<sub>2</sub>-mediated electrosynthesis. Although precious metal-based mixed metal oxides (MMOs) have been used as CER catalysts for more than half a century, they intrinsically suffer from a selectivity problem between the CER and parasitic oxygen evolution reaction (OER). Hence, the design of selective CER electrocatalysts is critically important. In this review, we provide an overview of the fundamental issues related to the electrocatalysis of the CER and design strategies for selective CER electrocatalysts. We present experimental and theoretical methods for assessing the active sites of MMO catalysts and the origin of the scaling relationship between the CER and the OER. We discuss kinetic analysis methods to understand the kinetics and mechanisms of CER. Next, we summarize the design strategies for new CER electrocatalysts that can enhance the reactivity of MMO-based catalysts and overcome their scaling relationship, which include the doping of MMO catalysts with foreign metals and the development of non-precious metal-based catalysts and atomically dispersed metal catalysts.</p>

MoS2 Nanostructures for Solar Hydrogen Generation via Membraneless Electrochemical Water Splitting

Storing and delivering green hydrogen generated by solar energy have the potential to significantly supplement and disburse the share of promising but intermittent renewable energy. In this scenario, robust materials capable of delivering solar-driven electrochemical water splitting for hydrogen generation provide an interesting protocol that is applicable to all sectors of energy. Electrochemical water splitting is the conventional and most prevalent technique for hydrogen generation, which utilizes platinum-based materials for the hydrogen evolution reaction (HER). However, these platinum-based noble metal catalysts possess poor cyclic stability, limiting their commercial application for economical hydrogen generation. Therefore, the development of efficient non-noble metal-based electrocatalysts is urgently needed to produce cost-competitive hydrogen energy. Several kinds of non-noble metal-based heterogeneous electrocatalysts, including carbides, sulfides, selenides, oxides, and phosphides, have been developed and studied. The unique physicochemical properties of carbonaceous materials make them promising candidates to support catalysts. In this paper, molybdenum disulfide (MoS2) nanomaterial catalysts have been synthesized, deposited on carbon fiber (CF)-based materials, and then used for solar hydrogen generation by membraneless electrochemical water splitting. At 430 W/m2 irradiation and 35 °C working temperature, the solar-to-hydrogen conversion efficiency is found to be 2.46%.

Effect of CO2/propane ratio and trimetallic oxide catalysts on maximizing dry reforming of propane

This study aimed at increasing the dry reforming reaction of propane with CO2 by using trimetallic oxide catalyst based on the reactive support of ZrO2/TiO2. Multiple basic (Mg, Be and Ba) and transition metal oxide (Cu, Fe) and Al were impregnated separately into 5%ZrO2/TiO2 catalyst support and characterized by XRD, BET, CO2-TPD and NH3-TPD. The catalysts showed an increase in the number of basic surface sites, with the trimetallic catalysts exhibiting more than 2.2–9.7 times the original number of basic sites of the Zr/Ti oxide support. In order to maximize greenhouse gas conversion, selected ratios of CO2/propane were correlated to increase syngas (CO and H2) product and promote more CO2 reactions via surface intermediates from CC bond dissociation of propane. Utilizing trimetallic catalysts enabled a three folds increase of CO yield compared to the reactive support used in the study. Although the selectivity towards H2 and CO increase with trimetallic catalysts, 2%Fe/5%ZrO2/TiO2 and 2%Be/5%ZrO2/TiO2 exhibited the highest propane dry reforming conversions (84–97%) with yields of H2 (35–51%) and CO (60–68%), respectively. The study demonstrated that each trimetallic oxide catalyst consumed CO2 differently, promoting distinct CC bond breaking patterns of propane over the catalyst surface.

Hydrogen spillover and substrate-support hydrogen bonding mediate hydrogenation of phenol catalyzed by palladium on reducible metal oxides.

Substrate-support interactions play an important role in the catalytic hydrogenation of phenolic compounds by ceria-supported palladium (Pd/CeO2). Here, we combine surface contrast solution NMR methods and reaction kinetic assays to investigate the role of substrate-support interactions in phenol (PhOH) hydrogenation catalyzed by titania-supported palladium (Pd/TiO2). We show that PhOH adsorbs on the catalyst via a weak hydrogen-bonding interaction between the -OH group of the substrate and one oxygen atom on the support. Interestingly, we observe that the addition of 20 mM inorganic phosphate results in a ∼2-fold destabilization of the PhOH-support interaction and a corresponding ∼2-fold inhibition of the catalytic reaction, suggesting an active role of the PhOH-TiO2 hydrogen bond in catalysis. A comparison of the data measured here with the results previously reported for a Pd/CeO2 catalyst indicates that the efficiency of the Pd-supported catalysts is correlated to the amount of PhOH hydrogen bonded to the metal oxide support. Since CeO2 and TiO2 have similar ability to uptake activated hydrogen from a noble metal site, these data suggest that hydrogen spillover is the main mechanism by which Pd-activated hydrogens are shuttled to the PhOH adsorbed on the surface of the support. Consistent with this hypothesis, Pd supported on a non-reducible metal oxide (silica) displays negligible hydrogenation activity. Therefore, we conclude that basic and reducible metal oxides are active supports for the efficient hydrogenation of phenolic compounds due to their ability to hydrogen bond to the substrate and mediate the addition of the activated hydrogens to the adsorbed aromatic ring.

The in situ phosphorization inducing oxygen vacancies in the core-shell structured NiFe oxides boosts the electrocatalytic activity for the oxygen evolution reaction.

Transition metal-based oxides have been reported as an important family of electrocatalysts for water splitting owing to their possible large-scale applications that are highly desirable for the hydrogen generation industry. Herein, we report a facile method for the preparation of phosphate-decorated NiFe oxides on nickel foam as efficient oxygen evolution reaction (OER) electrocatalysts for water oxidation. The OER electrocatalysts were developed through the pyrolysis of MIL(Fe) metal-organic frameworks (MOFs), which were modified with Ni and P species. It was found that the formation of NiO on the Fe2O3 surface (NiO@Fe2O3) can enrich electrocatalytic active sites for the OER. Meanwhile, the incorporation of P into NiO@Fe2O3 (Px-NiO@Fe2O3) creates abundant oxygen vacancies, which facilitates the surface charge transfer for OER electrocatalysis. Benefiting from the structure and composition advantages, P2.0-NiO@Fe2O3/NF exhibits the best performance for OER electrocatalysis among other prepared electrocatalysts, with an overpotential of 208 mV at the OER current density of 10 mA cm-2 and a small Tafel slope of 69.64 mV dec-1 in 1 M KOH solution. Additionally, P2.0-NiO@Fe2O3/NF shows an outstanding durability for the OER electrocatalysis, maintaining the OER current density above 20 mA cm-2 for more than 100 h.

Influence of Y2O3 reinforcement particles during heat treatment of IN718 composite produced by laser powder bed fusion

A metal matrix composite with Inconel 718 as the base metal and yttrium oxide (Y2O3) as the reinforcement particles was fabricated by the laser powder bed fusion technology. This paper presents a comprehensive study on the influence of the Y2O3 reinforcement particles on the microstructures and mechanical properties of the heat-treated printed composite. Complex precipitates formation between the Y2O3 nanoparticles and the carbonitride precipitates were shown. The complex precipitates separated into individual Y2O3 and titanium nitride (TiN) nanoparticles after heat treatment. Nano-sized Y-Ti-O precipitates were observed after solutionization due to the release of supersaturated Y in the metal matrix. Grain refinement was also observed in the heat-treated composites due to the high number of nano-sized precipitates. After solutionizing and aging, the grain size of the Y2O3-reinforced sample is 28.2% and 33.9% smaller, respectively, than that of the monolithic Inconel 718 sample. This effectively reduced the segregation of Nbat the grain boundaries and thus, γ′ and γ′′ precipitates were distributed in the metal matrix more homogeneously. Combined with the increased Orowan strengthening from a significantly higher number of nano-sized precipitates and grain boundary strengthening, the composite achieved higher yield strength, and ultimate tensile strength (1099.3 MPa and 1385.5 MPa, respectively) than those of the monolithic Inconel 718 (1015.5 MPa and 1284.3 MPa, respectively).

Base-metal oxide semiconductor electrodes for PPCP degradation: Ti-doped α-Fe2O3 for sulfosalicylic acid oxidation as an example

Sulfosalicylic acid is a typical pharmaceutical and personal care product with high toxicity, environmental persistence, and low biodegradability. Electrochemical oxidation has been demonstrated to be a promising way for hazardous organics treatment, but it is severely limited by the high cost and resource shortage of electrode materials. Base-metal oxide semiconductor anodes have the merits of low cost, diversity, and tunable energy levels for charge transfer, and thus may be alternatives to the electrodes for wastewater treatment. Herein, we found that Ti-doped α-Fe2O3, as an example, could be efficient for sulfosalicylic acid oxidation, reaching comparable faraday efficiency of sulfosalicylic acid to that of the boron-doped diamond electrode. Ti-doped electrodes exhibited both higher removal rates and current efficiency compared to the undoped. This could be mainly ascribed to the enhanced charge transfer rate constant. Kinetic analysis shows that the apparent reaction order, in terms of sulfosalicylic acid in bulk solution, depended on applied potential and pollutant concentration. Mechanism study shows that the oxidation of sulfosalicylic acid was mainly through indirect pathway. Moreover, the oxidation products were determined and the oxidation mechanism was proposed. This study may open a door to employ base-metal oxide semiconductor anodes for the efficient treatment of organic wastewater.