Increase Of Hydrothermal Temperature Research Articles

Reduction of graphene oxide (GO) to reduced graphene oxide (rGO) at different hydrothermal temperatures and enhanced photodegradation of zinc oxide/rGO composites

Scholars are shifting their attention to the development of environmentally friendly materials with a high degradability of environmental pollutants. Among various photocatalytic materials, zinc oxide (ZnO)/reduced graphene oxide (rGO) nanomaterials can meet these requirements. In this study, ZnO/rGO nanomaterials with different hydrothermal temperatures were fabricated through a hydrothermal method. We determined the hydrothermal temperature variations to create different structures and identify the morphologies and sizes of the ZnO/rGO material. The average crystal size of ZnO/rGO nanomaterials decreased from 32.25 nm to 30.30 nm when the hydrothermal temperature was increased from 100 °C to 180 °C. The detailed x-ray diffraction (XRD) study showed that the diffraction peak position of ZnO decreased, the lattice constant increased, and the unit cell volume increased with the increase in hydrothermal temperature. rGO-related diffraction peaks were also observed in the XRD patterns of ZnO/rGO samples, which indicates the formation of a ZnO/rGO crystalline structure. Fourier transform infrared spectra revealed the chemical bonding of ZnO and rGO materials. The photoluminescence (PL) spectra of ZnO/rGO nanocomposites presented two characteristic emission peaks at 383 and 558 nm. The Raman scattering spectra of ZnO/rGO nanomaterials exhibited ZnO-related peaks at 329, 436, and 1123 cm−1 and rGO-related peaks at 1352, 1579, 2706, and 2936 cm−1. The ultraviolet-visible (Vis) absorption spectra of ZnO/rGO nanomaterials manifested the characteristic absorption peaks of ZnO and rGO at 381 and 291 nm, respectively. The photocatalytic properties of ZnO/rGO nanomaterials were studied through the decomposition of methylene blue (MB) under Vis light. The effect of hydrothermal temperature on the properties of ZnO/rGO materials and the photodecomposition mechanism of MB were investigated in detail.

Influence of temperature and process water circulation on hydrothermal carbonization of food waste for sustainable fuel production

To address the challenge posed by energy shortages, this study focuses on the conversion of food waste (FW) into valuable resources. Employing hydrothermal carbonization (HTC) technology, the research successfully converted FW into an efficient solid fuel. Furthermore, it conducted an extensive investigation into how hydrothermal temperature (ranging from 180 to 260 °C) and the recycling of process water (repeated four times) influence the physical and chemical properties, as well as the combustion characteristics, of hydrochar fuel. The study's findings reveal that with an increase in hydrothermal temperature, the hydrochar yield decreases. However, this reduction can be mitigated by increasing the number of process water cycles. Notably, when the hydrothermal temperature surpasses 220 °C, the O/C and H/C ratios of hydrochar fall within the range characteristic of lignite, resulting in a higher heating value (HHV). Moreover, as the hydrothermal temperature and the number of process water cycles rise, the –C−(C, H)/CC bonds in aromatic vibrations become stronger, indicating the occurrence of aromaticization and polymerization reactions during this process. Hydrochar exhibits a more stable covalent cross-linked structure, which broadens its combustion range and reduces its reactivity. The combustion rate of hydrochar is significantly lower than that of FW, implying that it is more readily combustible. In summary, the utilization of HTC on FW and the recycling of process water can effectively transform it into a more stable solid fuel.

Enhanced corrosion resistance of layered double hydroxides/steam coating composite coating prepared by the hydrothermal method on LA43M magnesium–lithium alloy substrates

AbstractAn excellent anticorrosion Mg–Al layered double hydroxide (LDH) composite coating was successfully fabricated on LA43M magnesium alloy substrates via an in situ steam coating (SC) process and a subsequent hydrothermal treatment at different temperatures. The microstructure, composition and phase formation of the composite coatings were studied via X‐ray diffractometer, energy disperse spectroscopy, and scanning electron microscope, respectively. The corrosion resistance of composite coatings was further investigated using electrochemical measurements and corrosion test. The results showed that LDH/SC composite coating has typical nanosheets microstructure, which effectively seal the defects of SC. As the hydrothermal temperature increases, the thickness and density of nanosheets increases, and the corrosion resistance was significantly improved. Especially, the Mg–Al LDH/SC composite coating prepared at 100°C was the most dense and thickness, and exhibited the optimal and long‐term anticorrosion resistance in 3.5 wt.% NaCl soultion. It has the lowest Icorr (1.767 × 10−8 A/cm2), which decreased by three and two orders of magnitude compared with the bare substrate and SC. Furthermore, it can maintain good chemical stability after immersion in the corrosion medium for 192 h and its hydrogen evolution rate (0.00416 mL·cm−2·h−1) and weight lost rate (0.00266 mg·cm−2·h−1) were the lowest compared with other samples.

Microstructures and tribological properties of MoS2 overlayers on MAO Al alloy

To improve tribological properties of micro-arc oxidation (MAO) coating, MoS2 overlayers with self-lubricating effect were prepared by hydrothermal synthesis. The results showed that MoS2/MAO coating was mainly composed of MoS2, γ-Al2O3 and mullite phases. With an increase of hydrothermal temperature, crystallinity, thickness and continuity of the MoS2 overlayer were increased. E2 g/A1 g ratio in the Raman spectra experienced a decrease from 0.738 to 0.493. XPS and TEM analysis discovered that oxygen was incorporated into the MoS2 at lower hydrothermal temperature from incomplete decomposition of MoO42-. Wear tests evidenced a lower average COF and better self-lubricating effect in the MoS2 synthesized at lower temperature. It was concluded that oxygen-incorporation into the MoS2 improved self-lubricating effect due to alignment to basal-plane orientation.

Synthesis of Fe3O4/C composites derived from cornstalk by one-step hydrothermal method as a reusable adsorbent for dyes

The magnetic reusable Fe3O4/C composites were prepared derived from agriculture waste cornstalk and ferric nitrate through one-step hydrothermal method. In the preparation process, ferric nitrate was used as not only source of Fe3O4 but also catalyst to promote the generation of carbon nanomaterials from cornstalk avoiding the use of alkali agents and high temperature. The effect of hydrothermal temperature on the crystallite structure and size, magnetic property, adsorption activity of Fe3O4/C composites were mainly investigated. And, the adsorption kinetics and reusability of Fe3O4/C composites were studied. The result showed that the magnetic property increased with the increase of hydrothermal temperature due to the generation of Fe3O4 nanoparticles. Meanwhile, Fe3O4 nanoparticles improved the exfoliation of carbon nanosheets resulting in the increase of the specific surface areas and decrease of the active adsorption sites. Due to both effect of the specific surface areas and active adsorption sites, the adsorbed amount of Fe3O4/C composite increased while the removal rate decreased with the increase of hydrothermal temperature. All Fe3O4/C composites exhibited good adsorption performance to MB and RhB dyes. The removal rate of MB on Fe3O4/C composite with optimum hydrothermal temperature was about 56 % after five cycles, exhibiting good reusability.

Analysis of micro-particle effect and methanogenic potential of food waste model compounds by hydrothermal pretreatment

Anaerobic fermentation is one of the ways to realize the recycling, harmlessness and reduction of food waste. The potential of methane production via anaerobic fermentation was analyzed by the model compounds of food waste after hydrothermal pretreatment, and the micro-particle effect of hydrothermal pretreatment on matrix was verified by the change of physicochemical properties and morphology characteristics of model compounds of food waste in hydrothermal group, and the influence of hydrothermal pretreatment on anaerobic fermentation methane production was explored. From the perspective of particle size, the hydrothermal groups had good decomposition characteristics. With the increase of hydrothermal temperature, the surface morphology changed from smooth to rough, and the specific surface area increased from 0.29 m2·g−1 in the control group to 2.82 m2·g−1 in the hydrothermal group at 200 °C. In addition, the model compounds of food waste were anaerobic fermented under the condition of constant temperature water bath (55 °C). The results showed that the methane yield of 140 °C hydrothermal group was the highest (0.368 NL·g−1 VS), which increased by 27.78% compared with the control group, and the methane generation performance of the fermentation process was improved. Through material balance and energy analysis, it is revealed that hydrothermal pretreatment coupled anaerobic fermentation could achieve zero waste discharge and partial energy recovery.

Comparative study on the properties of wood vinegar prepared from the pretreated Chinese fir: Effect of hydrothermal parameters and hydrogen peroxide

Hydrothermal (HT) pretreatment and hydrothermal oxidative (HO) pretreatment are efficient in upgrading the quality of wood vinegar (WV), while little research pays attention to the systemic comparison between the effects of HT and HO pretreatment on the resulted WV. Therefore, in the present study, the response surface method is adopted first to analyze the effect of HT temperature, solid-to-liquid ratio (S/L), and retention time on the physicochemical properties of WV prepared from Chinese fir (CF). Then, the main compositions (hemicellulose, cellulose, and lignin) of the pretreated CF are quantitatively measured, and the comparative study between the effects of HT pretreatment and HO pretreatment on the yield, density, and compositions of the resulted WV is carried out based on CF composition. The results show that HT temperature is the main parameter that affects the physicochemical properties of the resulted WV. With the increase of HT temperature, the cellulose content of CF samples increases first at 180–230 °C and then decreases at 260–280 °C, the hemicellulose content decreases, and the lignin enriches. The cellulose enrichment gives rise to the increasing WV yield at 180–200 °C and the increasing WV density at 180–230 °C. While the dramatic cellulose decomposition at 230–280 °C results in the decreasing WV yield at 230–280 °C and the decreasing WV density at 260–280 °C. The cellulose is the main component that contributes to the yield and density of WV. Moreover, due to the cellulose enrichment, the contents of the organic compounds, especially the phenols, ketones, and aldehydes, increase dramatically at 180–230 °C, contributing to the lower pH value of the resulted WV. However, HO pretreatment aggravates the decomposition of CF components. During HO pretreatment, the decreases in the hemicellulose content and cellulose content are advanced to 160–200 °C and 180–230 °C respectively, and the lignin content increases. Thus, WV with the comparable yield and density to the unpretreated WV can be prepared at HO pretreatment temperature of 160 °C. Moreover, the pH value of WV decreases significantly after HO pretreatment of 160–200 °C because of the existence of the acid compounds with higher acidity in the resulted WV. Meanwhile, the content of the aldehydes contained in WV prepared from HO pretreated CS increases dramatically.

The Effect of the Hydrothermal Time and Temperature in the Synthesis to the Properties of Nitrogen-doped TiO2

Nitrogen-doped TiO2 (N-TiO2) has been synthesized through hydrothermal method by reacting the ethanolic solution of ethylene diamine with titanium precursor. The acidic contition was adjusted by the addition of glacial acetic acid. The hydrolysis process was done using hydrothermal process at various hydrothermal time and temperatures. The resulting materials were characterised FTIR, XRD, and Diffuse Refflectance UV/VIS Spectroscopy. The result showed that the increase of hydrothermal temperature lead to increase of particle size, but decreasing the band gap energy. However, the longer the hydrothermal time provided the decrease of particle size with no sugnificantly effect to the band gap energy.

Probing into crystallography and morphology properties of MoS2 nanoflowers synthesized via temperature dependent hydrothermal method

This paper reports the formation of flower-like hierarchical molybdenum disulfide (MoS2) nanoparticles following a simple one-step hydrothermal process with varying temperatures (200 °C and 220 °C). The as-synthesized particles were examined crystallographically by X-ray diffraction (XRD) method which revealed the formation of hexagonal MoS2 (2H-MoS2) and that the crystallite size of the particles increased with increasing hydrothermal temperature. Surface morphological characteristics of the particles were investigated by a field emission scanning electron microscope (FESEM) and interesting details were revealed such as the rounded 3D flower-like microstructure of the MoS2 particles and the petals of the flowers were composed of platelets built up by stacked-up MoS2 nanosheets. With the increase in hydrothermal temperature, the interlayer spacing of stacked layers of intense (002) plane is slightly decreased although the crystallinity of the material is improved. Both diameter and thickness of the nanoflowers and the nanoplatelets increased twice with increasing the temperatures. A visual crystallographic perspective was presented through simulation of 3D wireframe unit cell associated with the individual lattice planes as observed in the XRD pattern of the samples. In addition, a plausible growth mechanism is proposed for the formation of the obtained MoS2 nanoflowers on the basis of experimental observations and analysis.

Hydrothermal carbonization of alfalfa: role of processing variables on hydrochar properties.

Hydrothermal carbonization of alfalfa is a potential way to reuse agricultural waste. However, the effects of hydrothermal conditions on the properties of alfalfa-derived hydrochar are not clear. Herein, this study investigated the impact of different synthesis conditions (e.g., heating temperature, heating time, and solid to liquid ratio) on the formation and properties of hydrochar. Characterization and thermogravimetric analysis results revealed that with the increase of hydrothermal temperature and the extension of time, cellulose in alfalfa broken down more completely, and the number of carbon spheres and the aromatization degree increased, while the functional groups decreased. Furthermore, there was a surge in the carbon content, fixed carbon yield, high heating value, reduced oxygen, and volatile content. Additionally, the enhancement solid-liquid ratio could effectively improve the energy and mass yields. In all, by adjusting the process parameters of hydrochar, cleaner and higher productivity products could be obtained. This study provides theory basis for the production of target hydrochar that is used to soil amendments, adsorbents, and energy sources in the future.

Effect of CaO and hydrothermal carbonization conditions on the fuel characteristics of rice husk hydrochars.

The effects of hydrothermal temperature and catalyst concentration on the basic elements and combustion characteristics and kinetic parameters of hydrochars were investigated using ultimate analyzer and thermogravimetric method with rice husk as the research object and CaO as the additives. The results showed that: (1) the fixed carbon content of hydrochars gradually increased with the increase of hydrothermal temperature, whereas the volatile content gradually decreased. When CaO was added, the changes of fixed carbon and volatile fraction gradually decreased with the increase of hydrothermal temperature, and H/C atomic ratio increased to different degrees, which had a certain inhibitory effect on the degree of hydrothermal carbonization of rice husk. (2) The peak of the volatile fraction combustion section of hydrochars combustion derivative thermogravimetric curve was higher than that of the fixed carbon combustion section. CaO concentration has less effect on the volatile combustion section, and the combustion peak of the fixed carbon section is significantly reduced. (3) When the heating rate of the combustion test is accelerated, the ignition and burnout temperatures of the sample increase and the overall combustion curve shifts to the high temperature region. (4) The comprehensive combustion index SN decreases with the increase in hydrothermal temperature. When the hydrothermal temperature is certain, the CaO concentration causes the SN to increase and then decrease, which finally reduces the combustion performance of hydrochars. (5) The activation energy of the fixed carbon combustion section of hydrochars is lower than that of the volatile combustion section, and the activation energy of both volatile and fixed carbon combustion sections gradually decreases after adding CaO. The primary reaction kinetic model was used to describe the combustion kinetics of hydrochars, and the correlation coefficients (R2) were all above 0.92, and the results were reliable.

Synthesis and photocatalytic performance of three-dimensional flower-like bismuth tungstate: Influence of hydrothermal temperature

The three-dimensional (3D) flower-like Bi2WO6 photocatalysts were prepared by a facile hydrothermal method and characterized by X-ray diffraction (XRD), Ultraviolet–visible diffuse reflectance spectra (DRS), photoluminescence spectra (PL), scanning electron microscope (SEM), transmission electron microscope (TEM) and Brunauer Emmett Teller surface area (BET). The SEM and TEM images show that the Bi2WO6 presents 3D flower structure with an average diameter of 2–4 μm, which is composed of two-dimensional (2D) nanosheets. The increase of hydrothermal temperature is conducive to the separation of photogenerated charges, but is adverse to the surface area. Collectively, the Bi2WO6 obtained with hydrothermal temperature 160 °C exhibits the highest degradation degree towards methylene blue (MB) (80.6% after 60 min), which is higher than that of commercial P25 (74.3%).

In-situ preparation of palygorskite-montmorillonite materials from palygorskite mineral via hydrothermal process for high-efficient adsorption of aflatoxin B1

Due to the threats of mycotoxin-contaminated animal feeds to livestock farming, food safety and human health, Palygorskite-Montmorillonite (Pal-Mt) materials with different functional groups and microstructures have been studied as an effective mycotoxin adsorbent. In this study, Pal-Mt materials were controllably regulated from Pal mineral via hydrothermal process by adjusting the hydrothermal temperature. Along with the increase of hydrothermal temperature, the microstructure of Pal showed a gradual transformation from fiber to layer, which led to a fiber-layered structure. Batch aflatoxin B1 (AFB1) adsorption experiments were conducted at different conversion rates of Pal. The optimized Pal-Mt with 50% conversion of Pal exhibited satisfactory adsorption capacity of 13.17 mg/g and removal rate of 95.65% and 91.33% (only 33.09% and 26.27% for Pal) from 2 mg/L of AFB1 phosphate buffer solution at pH 3.5 and 6.5, respectively. The increasing adsorption capacity was mainly attributed to the synergistic effect of cations in the interlayer of Mt and the high specific area of Pal, resulting in a larger proportion of available adsorption sites (e.g., Ca2+, –OH), which favored bonding with AFB1 molecules. This work provides a new material regulated from abundant Pal mineral, which is effective and promising for adsorption of AFB1.

Facile Synthesis of 3D Sea Urchin-like CuO Microspheres Structures and its Higher Photocatalytic Properties

The three-dimensional (3D) sea urchin-like CuO microspheres structures were successfully synthesized by a simple hydrothermal method. With the hydrothermal temperature increases, the morphology of CuO micro-/nanostructures has changed: When the hydrothermal temperature reaches above 40 °C, the irregular CuO particles transform into a 3D sea urchin-like CuO microspheres. X-ray diffraction spectrum and Raman scatting spectra confirm that the obtained 3D sea urchin-like CuO microspheres at hydrothermal temperature of 60 °C are composed of a high purity and single-phase monoclinic CuO. It is found that the 3D sea urchin-like CuO microspheres structures exhibit the better photocatalytic property for degradation of methylene blue (MB) solution under the visible light irradiation compared to the irregular CuO particles, which duo to the relatively larger specific surface area of the sea urchin-like CuO microspheres structures, exposing more active sites and increasing the contact area between the catalyst and dye molecule. This remarkable photocatalytic performance of the 3D sea urchin-like CuO microspheres structures might has a promising application in waste water treatment.

The effect of hydrothermal temperature on the properties of SBA-15 materials

In present work, ordered mesoporous material SBA-15 was synthesized by using poly (alkylene oxide) block copolymer (Pluronic P123) as template and ethylsilicate as silica source in weak acid environment in a wide range of temperature. The focus of synthesis research was high hydrothermal temperature. The obtained products were characterized by various techniques, including XRD, N2 sorption isotherms, FTIR spectroscopy and thermogravimetric. The effect of hydrothermal temperature on the specific surface area, pore volume and pore size of SBA-15 products was investigated systematically. As the hydrothermal temperature increases from the 100–120 °C, the specific surface area and the pore volume of the mesoporous molecular sieve increase greatly. When the hydrothermal temperature increase further, the pore volume of the mesoporous molecular sieve increase continually. But the specific surface area decrease significantly. When the hydrothermal temperature is too high (over 140 °C), the order degree begins to decrease, So the specific surface area and pore volume decrease significantly because the pores structure have significant destruction and collapse. Mechanism and structural characteristics of P123 block copolymer could explain in detail the effect of hydrothermal temperature on the property and structure of mesoporous molecular sieve SBA-15.

Effect of TiO2 particle and pore size on DSSC efficiency

In this work, we report the preparation of TiO2 nanoparticles with a high surface area, from 120 to 168 m2 g−1 by the hydrothermal-microemulsion route and hydrothermal temperature effect over particle size, porosity, and photovoltaic parameter. The TiO2 samples were characterized by Raman, BET, TEM, SEM-FE, I–V curves, and EIS. The increase of hydrothermal temperature correlates with particle and pore size. Although when the synthesis temperature was 250 °C, the surface area presents an unexpected decrease of c.a. 28%. TiO2 samples were employed as thin-film photo-anodes for dye-sensitized solar cell (DSSC) solar cells. Photovoltaic results showed that the sample prepared at 250 °C presented the more suitable textural properties for the DSSC application. The prepared TiO2 materials with a particle size of 6.93 ± 0.59 nm and anatase crystalline phase favor electron transport and diffusion of electrolyte species, which directly impact in solar cell efficiency.

Molecular and microbial insights towards understanding the effects of hydrochar on methane emission from paddy soil

Directly returning rice straw to the paddy soil would significantly stimulate methane emission, and hydrochar has potential to be used as soil conditioner. However, the effects of hydrochar on the methane emission from paddy soil and the related mechanisms are still unclear. In the present study, straw-based hydrochar obtained at 200 °C (HC200), 250 °C (HC250) and 300 °C (HC300) and hydrochar after removal of bio-oil at these temperatures (CHC200, CHC250, and CHC300) were prepared and added to the paddy soil. The application of HC200, HC250 and HC300 resulted in the enhanced methane production compared to the control, showing 4.3, 1.6 and 1.5-fold higher methane production, respectively. It was related to the large amount of dissolved organic matter (DOM) released from hydrochar. Excitation-emission matrix fluorescence spectroscopy with parallel factor analysis (EEM-PARAFAC) showed that the hydrochar-derived DOM mainly included humic-like, phenolic and less aromatic structures, and with the increase of hydrothermal temperature, the content of humic-like substances and phenols increased, while biodegradable organics decreased. This was consistent with the maximum methane production by HC200. After incubation, there was no low-aromatic structures observed in the soil leachate, and the residual organics were mainly humus. The EEM-PARAFAC results were supported by compositional characterization of soil leachate by high-resolution mass spectrometry, and the refractory organics released from hydrochar was mainly lignins or (CRAM)-like structures in the range of H/C = 0.8–1.6 and O/C = 0.1–0.5. The organics dissolved from the washed hydrochar was significantly reduced, and some washed hydrochar (CHC250 and CHC300) even inhibited methane emission possibly due to their ability to adsorb organics. Microbial analysis further showed that the increased methane production resulted from hydrochar was associated with the enrichment of Janibacter, Anaeromyxobacter, Anaerolinea and Sporacetigenium. This present study provided a better understanding to the effect of hydrochar on methanogenesis in paddy soil.

Influence of synthesis parameters on the crystalline, structural, textural, optical and photocatalytic properties of α and β polymorphs of AgVO3 nanorods

The influence of synthesis conditions on the formation of α and β polymorphs of AgVO3, their crystalline, structural, textual and optical properties and photocatalytic activity for dye degradation was investigated. The as-prepared polymorphs were characterized by using XRD, FTIR, EDX, SEM, TEM, HRTEM, XPS, BET and UV–vis. analyses. The analytical results indicated that a metastable α-AgVO3 was formed in the precipitation method, whereas it was irreversibly converted into thermodynamically stable β-AgVO3 by a hydrothermal method at 120 °C. The hydrothermal treatment was found to be decisive for the formation of β-form with high crystallinity and phase purity. The increase of hydrothermal temperature to 150 °C and 180 °C could not contributed to a significant variation in the crystalline, structural, textural and optical properties of the β-AgVO3. Moreover, a plausible mechanism for the phase transformation was briefly discussed. A combination of the needle and rod-like nanostructures of α form was completely changed to nanorods in β form after hydrothermal treatment. The optical band gap of α and β AgVO3 polymorphs was found to be 1.91 eV and 1.98 eV respectively. The photocatalytic activity of the silver vanadates for the degradation of Rhodamine B indicated that β-AgVO3 nanorods were better than α-AgVO3 polymorphs. This could be attributed to the significant effects of its stable crystalline structure rather than specific surface area. Moreover, due to the reduced grain boundaries in β-form, their electron-hole recombination rate was lowed compared to α form. The degradation efficiency reached to 56% within 180 min under visible light irradiation. However, the increase of hydrothermal temperature does not have a significant effect in the photocatalytic activity. Moreover, the β-AgVO3 nanorods were successfully reused for five cycles of photodegradation.

{0 0 1}-Facet-Exposed Ag4V2O7 Nanoplates: Additive-Free Hydrothermal Synthesis and Enhanced Photocatalytic Activity

The synthesis of silver pyrovanadate, Ag4V2O7, nanoplates with exposed {0 0 1}-facets by a facile, additive-free hydrothermal method was described in this paper. The photocatalytic activity of rhodamine B over Ag4V2O7 samples under solar light irradiation was also evaluated. By using an equimolar mixture of NH4VO3 and AgNO3 with the presence of a suitable amount of ammonia, Ag4V2O7 nanoplates were obtained readily and purely at temperatures from 100 to 140°C for 4 h. In particular, the c-axis orientation growth of Ag4V2O7 nanoplates occurred and increased monotonously with temperatures in the range of over 100 up to 140°C. Further increase in hydrothermal temperature up to 220°C, the Ag4V2O7 phase no longer existed and the β-AgVO3 phase was formed instead. The photocatalytic activity of the optimized Ag4V2O7 sample comprising {0 0 1}-facet-exposed nanoplates with the highest degree of orientation was significantly higher than that of the random-oriented sample. The effects of using ammonia as a complexing agent on the structure, microstructure, texture, exposed facet, and photocatalytic activity of Ag4V2O7 samples were also investigated for the first time.

Fundamental Study of Carbon Materials Derived from Empty Fruit Bunch via Hydrothermal Carbonization

The utilization of biomass has recently gained great attention in recent years owing to growth of global environmental concerns. The aim of this work is to study the morphology of carbon materials derived from biomass oil palm empty fruit bunch (EFB) via hydrothermal carbonization (HTC) at different temperatures (160 - 200 °C) and times (4 - 12 h) followed by carbonization at 300 - 900 °C under nitrogen atmosphere for 2 h. The physiochemical properties of carbon sample were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and surface area analysis. The results demonstrated that the increase of hydrothermal temperature, hydrothermal time, and carbonization temperature resulted in the formation of carbon materials with higher surface area, porosity and carbon content. Our results revealed that carbon derived from EFB via HTC at optimal condition exhibited porous structure with high surface area, which can be further applied for absorbent applications.