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3 pages, 182 KiB

Open AccessEditorial

Hybrid Porous Nanomaterials for Energy and Environment

by Evangelos P. Favvas

Nanomaterials 2022, 12(14), 2471; https://doi.org/10.3390/nano12142471 - 19 Jul 2022

Viewed by 892

Abstract

Porous materials have applications in a wide range of research and industrial processes [...] Full article

(This article belongs to the Special Issue Hybrid Porous Nanomaterials for Energy and Environment)

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15 pages, 5167 KiB

Open AccessArticle

Electrochemical Impedance as an Assessment Tool for the Investigation of the Physical and Mechanical Properties of Graphene-Based Cementitious Nanocomposites

by Eirini Tziviloglou, Zoi S. Metaxa, George Maistros, Stavros K. Kourkoulis, Dionysios S. Karousos, Evangelos P. Favvas and Nikolaos D. Alexopoulos

Nanomaterials 2023, 13(19), 2652; https://doi.org/10.3390/nano13192652 - 27 Sep 2023

Viewed by 831

Abstract

This investigation explores the potential of electrochemical impedance spectroscopy (EIS) in evaluating graphene-based cementitious nanocomposites, focusing on their physical and structural properties, i.e., electrical resistivity, porosity, and fracture toughness. EIS was employed to study cement mixtures with varying graphene nanoplatelet (xGnP) concentrations (0.05–0.40% [...] Read more.

This investigation explores the potential of electrochemical impedance spectroscopy (EIS) in evaluating graphene-based cementitious nanocomposites, focusing on their physical and structural properties, i.e., electrical resistivity, porosity, and fracture toughness. EIS was employed to study cement mixtures with varying graphene nanoplatelet (xGnP) concentrations (0.05–0.40% per dry cement weight), whereas flexural tests assessed fracture toughness and porosimetry analyses investigated the structural characteristics. The research demonstrated that the electrical resistivity initially decreased with increasing xGnP content, leveling off at higher concentrations. The inclusion of xGnPs correlated with an increase in the total porosity of the cement mixtures, which was indicated by both EIS and porosimetry measurements. Finally, a linear correlation emerged between fracture toughness and electrical resistivity, contributing also to underscore the use of EIS as a potent non-destructive tool for evaluating the physical and mechanical properties of conductive nano-reinforced cementitious nanocomposites. Full article

(This article belongs to the Special Issue Hybrid Porous Nanomaterials for Energy and Environment)

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19 pages, 4062 KiB

Open AccessFeature PaperArticle

Chromium(VI) Removal from Water by Lanthanum Hybrid Modified Activated Carbon Produced from Coconut Shells

by Athanasia K. Tolkou, Soultana Trikalioti, Olina Makrogianni, Maria Xanthopoulou, Eleni A. Deliyanni, Ioannis A. Katsoyiannis and George Z. Kyzas

Nanomaterials 2022, 12(7), 1067; https://doi.org/10.3390/nano12071067 - 24 Mar 2022

Cited by 16 | Viewed by 2128

Abstract

Cr(VI) is considered to be the most hazardous and toxic oxidation state of chromium and hence the development of effective removal technologies, able to provide water with Cr(VI) below the drinking water limits (US EPA 100 μg/L, European Commission 50 μg/L, which will [...] Read more.

Cr(VI) is considered to be the most hazardous and toxic oxidation state of chromium and hence the development of effective removal technologies, able to provide water with Cr(VI) below the drinking water limits (US EPA 100 μg/L, European Commission 50 μg/L, which will be reduced to 25 by 2036) is a very important issue in water treatment. This study aimed at examining the performance of activated carbon produced from coconut shells, modified by lanthanum chloride, for Cr(VI) removal from waters. The structure of the formed material (COC-AC-La) was characterized by the application of BET, FTIR and SEM techniques. The effect of the adsorbent’s dosage, pH value, contact time, initial Cr(VI) concentration and water matrix was examined with respect to Cr(VI) removal. The results indicated that the maximum Cr(VI) removal was observed at pH 5; 4 h contact time and 0.2 g/L of adsorbent’s dosage was adequate to reduce Cr(VI) from 100 μg/L to below 25 μg/L. Freundlich isotherm and pseudo-second order kinetic models fitted the experimental data sufficiently. The maximum adsorption capacity achieved was 6.3 μg/g at pH 5. At this pH value, the removal percentage of Cr(VI) reached 95% for an initial Cr(VI) concertation of 30 μg/L. At pH 7 the corresponding efficiency was roughly 60%, resulting in residual Cr(VI) concentrations below the anticipated drinking water limit of 25 μg/L of total chromium, when the initial Cr(VI) concentration was 50 μg/L. Consecutive adsorption and regeneration studies were conducted using 0.01 M of NaOH as an eluent to evaluate the reusability of the adsorbents, Results showed 20% decrease of adsorption capacity after 5 regeneration cycles of operation. Full article

(This article belongs to the Special Issue Hybrid Porous Nanomaterials for Energy and Environment)

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16 pages, 4184 KiB

Open AccessFeature PaperArticle

Dispersion of Multi-Walled Carbon Nanotubes into White Cement Mortars: The Effect of Concentration and Surfactants

by Zoi S. Metaxa, Spyridoula Boutsioukou, Maria Amenta, Evangelos P. Favvas, Stavros K. Kourkoulis and Nikolaos D. Alexopoulos

Nanomaterials 2022, 12(6), 1031; https://doi.org/10.3390/nano12061031 - 21 Mar 2022

Cited by 26 | Viewed by 2672

Abstract

Multi-wall carbon nanotubes (MWCNTs) exhibit exceptional mechanical and electrical properties and can be used to improve the mechanical and piezoelectric properties of cement-based materials. In the present study, the effect of different MWCNT concentrations as well as different types of surfactants and a [...] Read more.

Multi-wall carbon nanotubes (MWCNTs) exhibit exceptional mechanical and electrical properties and can be used to improve the mechanical and piezoelectric properties of cement-based materials. In the present study, the effect of different MWCNT concentrations as well as different types of surfactants and a superplasticizer were examined to reinforce, at the nanoscale, a white cement mortar typically used for the restoration of monuments of cultural heritage. It was shown that sodium dodecylbenzenesulfonate (SDBS) and Triton X-100 surfactants slightly decreased the white cement mortars’ electrical resistivity (by an average of 10%), however, the mechanical properties were essentially decreased by an average of 60%. The most suitable dispersion agent for the MWCNTs proved to be the superplasticizer Ceresit CC198, and its optimal concentration was investigated for different MWCNT concentrations. Carboxylation of the MWCNT surface with nitric acid did not improve the mechanical performance of the white cement nanocomposites. The parametric experimental study showed that the optimum combination of 0.8 wt% of cement superplasticizer and 0.2 wt% of cement MWCNTs resulted in a 60% decrease in the electrical resistivity; additionally, the flexural and compressive strengths were both increased by approximately 25% and 10%, respectively. Full article

(This article belongs to the Special Issue Hybrid Porous Nanomaterials for Energy and Environment)

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15 pages, 3284 KiB

Open AccessArticle

CFD Development of a Silica Membrane Reactor during HI Decomposition Reaction Coupling with CO₂ Methanation at Sulfur–Iodine Cycle

by Milad Mohammad Alinejad, Kamran Ghasemzadeh, Adolfo Iulianelli, Simona Liguori and Milad Ghahremani

Nanomaterials 2022, 12(5), 824; https://doi.org/10.3390/nano12050824 - 28 Feb 2022

Cited by 2 | Viewed by 1804

Abstract

In this work, a novel structure of a hydrogen-membrane reactor coupling HI decomposition and CO₂ methanation was proposed, and it was based on the adoption of silica membranes instead of metallic, according to their ever more consistent utilization as nanomaterial for hydrogen [...] Read more.

In this work, a novel structure of a hydrogen-membrane reactor coupling HI decomposition and CO₂ methanation was proposed, and it was based on the adoption of silica membranes instead of metallic, according to their ever more consistent utilization as nanomaterial for hydrogen separation/purification. A 2D model was built up and the effects of feed flow rate, sweep gas flow rate and reaction pressure were examined by CFD simulation. This work well proves the feasibility and advantage of the membrane reactor that integrates HI decomposition and CO₂ methanation reactions. Indeed, two membrane reactor systems were compared: on one hand, a simple membrane reactor without proceeding towards any CO₂ methanation reaction; on the other hand, a membrane reactor coupling the HI decomposition with the CO₂ methanation reaction. The simulations demonstrated that the hydrogen recovery in the first membrane reactor was higher than the methanation membrane reactor. This was due to the consumption of hydrogen during the CO₂ methanation reaction, occurring in the permeate side of the second membrane reactor system, which lowered the amount of hydrogen recovered in the outlet streams. After model validation, this theoretical study allows one to evaluate the effect of different operating parameters on the performance of both the membrane reactors, such as the pressure variation between 1 and 5 bar, the feed flow rate between 10 and 50 mm³/s and the sweep gas flow rate between 166.6 and 833.3 mm³/s. The theoretical predictions demonstrated that the best results in terms of HI conversion were 74.5% for the methanation membrane reactor and 67% for the simple membrane reactor. Full article

(This article belongs to the Special Issue Hybrid Porous Nanomaterials for Energy and Environment)

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11 pages, 3533 KiB

Open AccessArticle

Electronic Structure and d-Band Center Control Engineering over Ni-Doped CoP₃ Nanowall Arrays for Boosting Hydrogen Production

by Jing Qi, Tianli Wu, Mengyao Xu, Dan Zhou and Zhubing Xiao

Nanomaterials 2021, 11(6), 1595; https://doi.org/10.3390/nano11061595 - 17 Jun 2021

Cited by 5 | Viewed by 2369

Abstract

To address the challenge of highly efficient water splitting into H₂, successful fabrication of novel porous three-dimensional Ni-doped CoP₃ nanowall arrays on carbon cloth was realized, resulting in an effective self-supported electrode for the electrocatalytic hydrogen-evolution reaction. The synthesized samples [...] Read more.

To address the challenge of highly efficient water splitting into H₂, successful fabrication of novel porous three-dimensional Ni-doped CoP₃ nanowall arrays on carbon cloth was realized, resulting in an effective self-supported electrode for the electrocatalytic hydrogen-evolution reaction. The synthesized samples exhibit rough, curly, and porous structures, which are beneficial for gaseous transfer and diffusion during the electrocatalytic process. As expected, the obtained Ni-doped CoP₃ nanowall arrays with a doping concentration of 7% exhibit the promoted electrocatalytic activity. The achieved overpotentials of 176 mV for the hydrogen-evolution reaction afford a current density of 100 mA cm⁻², which indicates that electrocatalytic performance can be dramatically enhanced via Ni doping. The Ni-doped CoP₃ electrocatalysts with increasing catalytic activity should have significant potential in the field of water splitting into H₂. This study also opens an avenue for further enhancement of electrocatalytic performance through tuning of electronic structure and d-band center by doping. Full article

(This article belongs to the Special Issue Hybrid Porous Nanomaterials for Energy and Environment)

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14 pages, 2057 KiB

Open AccessArticle

Solar-Powered Photodegradation of Pollutant Dyes Using Silver-Embedded Porous TiO₂ Nanofibers

by Jerry Zhi Xiong Heng, Karen Yuanting Tang, Michelle D. Regulacio, Ming Lin, Xian Jun Loh, Zibiao Li and Enyi Ye

Nanomaterials 2021, 11(4), 856; https://doi.org/10.3390/nano11040856 - 27 Mar 2021

Cited by 25 | Viewed by 2725

Abstract

Titanium dioxide (TiO₂) nanomaterials have been ubiquitously investigated as a photocatalyst for organic contaminant treatment in wastewater due to their exemplary semiconductor properties. However, their huge band gap remains a barrier for visible light absorption, limiting their utility in practical applications. [...] Read more.

Titanium dioxide (TiO₂) nanomaterials have been ubiquitously investigated as a photocatalyst for organic contaminant treatment in wastewater due to their exemplary semiconductor properties. However, their huge band gap remains a barrier for visible light absorption, limiting their utility in practical applications. The incorporation of noble metals in the TiO₂ scaffold would help mitigate the problem via plasmonic resonance enhancements. Silver (Ag) is the chosen noble metal as it is relatively cheap and has great plasmonic effects. In this study, the use of electrospun Ag-embedded TiO₂ nanofibers as a photocatalyst is shown to be effective in decomposing rhodamine B and methyl orange dyes under a solar simulator in 3 h, which is more efficacious as opposed to pristine TiO₂ nanofibers. This showcases the potential of a simple and economic wastewater treatment system for the removal of organic pollutants. Full article

(This article belongs to the Special Issue Hybrid Porous Nanomaterials for Energy and Environment)

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10 pages, 1868 KiB

Open AccessArticle

Coating of Conducting and Insulating Threads with Porous MOF Particles through Langmuir-Blodgett Technique

by Sakandar Rauf, Miguel A. Andrés, Olivier Roubeau, Ignacio Gascón, Christian Serre, Mohamed Eddaoudi and Khaled N. Salama

Nanomaterials 2021, 11(1), 160; https://doi.org/10.3390/nano11010160 - 10 Jan 2021

Cited by 3 | Viewed by 3071

Abstract

The Langmuir-Blodgett (LB) method is a well-known deposition technique for the fabrication of ordered monolayer and multilayer thin films of nanomaterials onto different substrates that plays a critical role in the development of functional devices for various applications. This paper describes detailed studies [...] Read more.

The Langmuir-Blodgett (LB) method is a well-known deposition technique for the fabrication of ordered monolayer and multilayer thin films of nanomaterials onto different substrates that plays a critical role in the development of functional devices for various applications. This paper describes detailed studies about the best coating configuration for nanoparticles of a porous metal-organic framework (MOF) onto both insulating or conductive threads and nylon fiber. We design and fabricate customized polymethylmethacrylate sheets (PMMA) holders to deposit MOF layers onto the threads or fiber using the LB technique. Two different orientations, namely, horizontal and vertical, are used to deposit MIL-96(Al) monolayer films onto five different types of threads and nylon fiber. These studies show that LB film formation strongly depends on deposition orientation and the type of threads or fiber. Among all the samples tested, cotton thread and nylon fiber with vertical deposition show more homogenous monolayer coverage. In the case of conductive threads, the MOF particles tend to aggregate between the conductive thread’s fibers instead of forming a continuous monolayer coating. Our results show a significant contribution in terms of MOF monolayer deposition onto single fiber and threads that will contribute to the fabrication of single fiber or thread-based devices in the future. Full article

(This article belongs to the Special Issue Hybrid Porous Nanomaterials for Energy and Environment)

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