The coordination microenvironment of metal active sites in metal–organic frameworks (MOFs) plays a crucial role in its performance for electrochemical CO2 reduction reaction (CO2RR). However, it ...remains a challenge to clarify the structure–performance relationship for CO2RR catalyzed by MOFs. Herein, a series of MOFs with different coordination microenvironments of Cu(I) sites (CuCl, CuBr, and CuI) to evaluate their performances for CO2RR is synthesized. With the increasing radius of halogen atom, the CO2 adsorption capacity increases and d‐band center of Cu positively shifts to the Fermi level, leading to enhance the selectivity of CO2 to CH4 conversion. CuI gives the highest total Faradaic efficiency (FE) of 83.2%, with a FE of CH4 up to 57.2% and CH4 partial current density of 60.7 mA cm−2 at −1.08 V versus reversible hydrogen electrode. Theoretical calculations reveal that the shifted d‐band center of Cu site contributes to reduced formation energies of *CH2O and *CH3O intermediates, which is the potential‐determining step of CO2RR and thus facilitates the electrocatalytic CO2 reduction to CH4. This study opens a new avenue for studying the relationship between the coordination microenvironment of active site and electroreduction reaction performance of MOFs.
Exploring the structure−performance relationship of electrocatalytic CO2 reduction on metal–organic frameworks (MOFs) remains a challenge. Herein, a series of stable MOFs (CuCl, CuBr, CuI) are synthesized and comprehensive analysis is undertaken to reveal the relationship between the coordination microenvironment of Cu active site and performance of converting CO2 to CH4.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Biochar is a solid by-product of thermochemical conversion of biomass to bio-oil and syngas. It has a carbonaceous skeleton, a small amount of heteroatom functional groups, mineral matter, and water. ...Biochar’s unique physicochemical structures lead to many valuable properties of important technological applications, including its sorption capacity. Indeed, biochar’s wide range of applications include carbon sequestration, reduction in greenhouse gas emissions, waste management, renewable energy generation, soil amendment, and environmental remediation. Aside from these applications, new scientific insights and technological concepts have continued to emerge in the last decade. Consequently, a systematic update of current knowledge regarding the complex nature of biochar, the scientific and technological impacts, and operational costs of different activation strategies are highly desirable for transforming biochar applications into industrial scales. This communication presents a comprehensive review of physical activation/modification strategies and their effects on the physicochemical properties of biochar and its applications in environment-related fields. Physical activation applied to the activation of biochar is discussed under three different categories: I) gaseous modification by steam, carbon dioxide, air, or ozone; II) thermal modification by conventional heating and microwave irradiation; and III) recently developed modification methods using ultrasound waves, plasma, and electrochemical methods. The activation results are discussed in terms of different physicochemical properties of biochar, such as surface area; micropore, mesopore, and total pore volume; surface functionality; burn-off; ash content; organic compound content; polarity; and aromaticity index. Due to the rapid increase in the application of biochar as adsorbents, the synergistic and antagonistic effects of activation processes on the desired application are also covered.
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•Biochar modified by non-thermal plasma was investigated for Hg0 adsorption.•The chlorine-functional groups were increased on biochars by chlorine plasma.•CCl groups served as ...activated sites and dominated Hg0 removal in biochars.•Chlorine plasma increased the Hg0 removal efficiency of all modified biochars.•T6Cl exhibited the highest Hg0 adsorption capacity of 583.0µg/g in 90min.
Biochar, known as a byproduct of biomass pyrolysis, was prepared from rice straw (R6), tobacco straw (T6), corn straw (C6), wheat straw (W6), millet straw (M6), and black bean straw (B6) in high purity nitrogen at 600°C. Chlorine (Cl) non-thermal plasma was used to increase Cl active sites on biochar to promote the mercury removal efficiency. The physio-chemical properties of biochar were characterized by proximate analysis, ultimate analysis, BET, SEM, TGA, FTIR, and XPS. Modification by chlorine plasma increased the Hg0 removal efficiency of the biochar from around 8.0% to 80.0%. The Hg0 adsorption capacity of T6 was 36 times higher after Cl2 plasma modification. Plasma caused the biochar surface to become porous and promoted the thermal stability of the biochar. Sulfur (S) content remained in the range of 0.5–0.7%, elemental/organic sulfur and sulfide were converted to sulfate during plasma treatment. The relative intensity of the oxygen functional groups (CO, CO and C(O)OC) were enhanced, while the content of oxygen (O) in biochar decreased. The main reason for the improved mercury removal efficiency by modified biochars was attributed to the increased number of CCl groups on the surface of the biochars induced by Cl2 plasma. The CCl groups functioned as activated sites and promoted the Hg0 removal efficiency.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Renewable energy sources e.g. biofuels, are the focus of this century. Economically and environmental friendly production of such energies are the challenges that limit their usages. Microalgae is ...one of the most promising renewable feedstocks. However, economical production of microalgae lipid in large scales is conditioned by increasing the lipid content of potential strains without losing their growth rate or by enhancing both simultaneously. Major effort and advances in this area can be made through the environmental stresses. However, such stresses not only affect the lipid content and species growth (biomass productivity) but also lipid composition. This study provides a comprehensive review on lipid enhancement strategies through environmental stresses and the synergistic or antagonistic effects of those parameters on biomass productivity and the lipid composition. This study contains two main parts. In the first part, the cellular structure, taxonomic groups, lipid accumulation and lipid compositions of the most potential species for lipid production are investigated. In the second part, the effects of nitrogen deprivation, phosphorus deprivation, salinity stress, carbon source, metal ions, pH, temperature as the most important and applicable environmental parameters on lipid content, biomass productivity/growth rate and lipid composition are investigated.
•Cellular structure and taxonomy of potential microalgae for biofuel production were considered.•The quality of lipid accumulation and lipid compositions of those strains were investigated.•The effect of environmental stressors on lipid enhancement in those strains was investigated.•The effect of stressors on biomass productivity and lipid composition was investigated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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•In organometallic catalytic chemistry, most catalysts are dissolved in organic solvents to ensure their activity.•The catalysts, however, cannot be recycled from the reaction system ...after several turnovers, which is a waste of the noble metals.•Metal–organic frameworks (MOFs), with the periodic order and site isolation of the catalytic struts, eliminate the multimolecular catalyst deactivation, thus extending the catalytic centers’ functional lifetime.•Meanwhile, MOFs can facilitate reactions like enzymatic catalysis due to their organization of the reactants in suitable positions and their ability to minimize the entropy loss and to reduce the transition-state energy.•In this review, typical examples of MOF-catalyzed reactions are given to show the increasingly visible advantage of MOFs in catalytic reactions.•Classification of the catalytic centers, how they work for various reactions in porous MOFs, as well as how to control their selectivity and activity will be discussed in detail.•Furthermore, functional groups introduced to MOFs by different post-synthetic catalytic reactions are discussed thoroughly.
Metal-organic frameworks (MOFs), as a new stable class of hybrid materials synthesized, regulated and decorated by rational incorporating organic bridging ligands and metal ions with well-defined coordination geometry have become promising candidates for heterogeneous catalysis in industrial applications. Compared with homogeneous catalysts, MOF catalysts can be easily recycled and reused for several times; while compared with traditional heterogeneous catalysts, they possess tunable size and catalytic centers via exchange or modification of their components. This review will sketch typical successful MOF-catalyzed reactions and summarize various catalytic centers, including the open metal sites, bifunctional acid-base sites in MOFs, as well as catalytic centers introduced to MOFs via PSM. The periodic order and site isolation of the catalytic struts in MOFs eliminate the multimolecular catalyst deactivation pathways to extend the catalytic centers’ functional lifetime and facilitate the studies of their activities and reaction mechanisms. Furthermore, detailed discussion on how the catalytic centers play the roles in the catalytic reactions and how to control the activity and selectivity of them will be given via typical reported examples.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Palladium (Pd) nanostructures are highly active non‐platinum anodic electrocatalysts in alkaline direct methanol fuel cells (ADMFCs) and their electrocatalytic performance relies highly on their ...morphology and composition. Herein, a facile high‐temperature pyrolysis method to synthesize high‐quality Pd‐palladium oxide (PdO) porous nanotubes (PNTs) by using Pd(II)‐dimethylglyoxime complex (Pd(II)‐DMG) nanorods as a self‐template is reported. The chemical component of pyrolysis products highly correlates with pyrolysis temperature. The electrochemical measurements and density functional theory calculations show the existence of PdO enhances the electroactivity of metallic Pd for both methanol oxidation reaction (MOR) and carbon monoxide oxidation reaction in alkaline media. Benefiting from its one‐dimensionally porous architecture and evident synergistic effect between PdO and Pd (e.g., electronic effect and bifunctional mechanism), Pd‐PdO PNTs achieve a 3.7‐fold mass activity enhancement and improved durability for MOR compared to commercial Pd nanocrystals. Considering the simple synthesis, excellent activity, and long‐term stability, Pd‐PdO PNTs may be highly promising anodic electrocatalysts in ADMFCs.
High‐quality porous palladium (Pd)‐palladium oxide (PdO) nanotubes are synthesized via a facial Pd(II)‐dimethylglyoxime complex nanorods‐induced self‐template method. Benefiting from the one‐dimensionally porous architecture and evident synergistic effect between PdO and Pd, the Pd‐PdO nanotubes achieve a 3.7‐fold mass activity enhancement and improved durability for methanol oxidation reaction compared to commercial Pd nanocrystals, revealing a highly promising robust anodic electrocatalyst in alkaline direct methanol fuel cells.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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•An aminated GO for CO2 adsorption was prepared by a novel ultrasound-enhanced amine-functionalization method.•The ultrasound irradiation was very effective in the interaction between ...the amine and the oxygen-containing groups of GO.•The thermal resistance property of aminated GO makes it ideal candidate for CO2 adsorption from flue gas.•The aminated GO exhibited a better adsorption capacity of 1.2 mmol g−1 of adsorbent in the flue gas temperature (338 K).
The present study discusses a novel ultrasound promoted amination technique to functionalize graphene oxide (GO) for CO2 adsorption. Graphene oxide was synthesized following the modified Hummer’s method. The developed functionalization technique integrates the advantages of low-frequency ultrasonic physical activation with the chemical functionalization using tetraethylenepentamine (TEPA). Acoustic treatment exfoliates the clusters of graphene oxide and enhances the surface area for the subsequent amine functionalization and CO2 adsorption. Changes in textural properties, surface functionalities, thermal stability, and elemental compositions were examined before and after activation of graphene oxide. The characterization results revealed substantial increment of N content, from 0.08 in pristine to 4.84% in functionalized GO and the subsequent reduction in surface area from 289 to 198 m2/g in the functionalized GO, indicating attachment of TEPA to GO structure. CO2 adsorption experiments were conducted under diluted CO2 with the partial pressure of 0.10 atm. at 338 K and the results revealed that ultrasonic-TEPA activated GO possessed enhanced adsorption capacity of 1.2 mmol g−1 over pristine GO. While pristine GO could only achieve the maximum adsorption capacity of 0.3 mmol g−1 at 303 K. Besides, the sonochemically modified adsorbent showed stable cyclic adsorption-regeneration performance with only 1% reduction in adsorption capacity after 10 cycles. Finally, the effectiveness of the developed physicochemical activation technique was determined by comparing its adsorption capacity with the adsorbents found from literature.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•This paper provides an exhaustive and comprehensive survey of phase shifting techniques used for fringe projection profilometry.•The basic principles of several state-of-the-art phase shifting ...profilometry algorithms are reviewed.•Typical error sources in phase measurement for a phase shifting profilometry system are reviewed and discussed.•The advantages and drawbacks of different algorithms are summarized to provide a useful guide to the selection of the most appropriate technique for a particular application.
The principle of structured light and triangulation is used in a wide range of 3D optical metrology applications, such as mechanical engineering, industrial monitoring, computer vision, and biomedicine. Among a multitude of techniques based on this principle, phase shifting profilometry (PSP) plays a dominant role due to its high attainable measurement accuracy, spatial resolution, and data density. Over the past few decades, many PSP algorithms have been proposed in the literature in order to achieve higher measurement accuracy, lower pattern count, and/or better robustness to different error sources. Besides, many unconventional PSP codification techniques address the problem of absolute phase recovery with few projected patterns, allowing for high-efficiency measurement of objects containing isolated regions or surface discontinuities. In this paper, we present an overview of these state-of-the-art phase shifting algorithms for implementing 3D surface profilometry. Typical error sources in phase measurement for a phase shifting system are discussed, and corresponding solutions are reviewed. The advantages and drawbacks of different PSP algorithms are also summarized to provide a useful guide to the selection of the most appropriate phase shifting technique for a particular application.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Biochar (BC) generated from thermal and hydrothermal cracking of biomass is a carbon-rich product with the microporous structure. The graphene-like structure of BC contains different chemical ...functional groups (e.g. phenolic, carboxylic, carbonylic, etc.), making it a very attractive tool for wastewater treatment, CO
capture, toxic gas adsorption, soil amendment, supercapacitors, catalytic applications, etc. However, the carbonaceous and mineral structure of BC has a potential to accept more favorable functional groups and discard undesirable groups through different chemical processes. The current review aims at providing a comprehensive overview on different chemical modification mechanisms and exploring their effects on BC physicochemical properties, functionalities, and applications. To reach these objectives, the processes of oxidation (using either acidic or alkaline oxidizing agents), amination, sulfonation, metal oxide impregnation, and magnetization are investigated and compared. The nature of precursor materials, modification preparatory/conditions, and post-modification processes as the key factors which influence the final product properties are considered in detail; however, the focus is dedicated to the most common methods and those with technological importance.
This study investigates the potential of cow dung, an animal manure, as a binder to enhance the physicochemical properties of the base pellet (a mixture of wheat straw and rice husk). In the first ...step, preliminary experiments were performed to select the best composition of wheat straw and rice husk for the base pellet. The selection was based on calorific value. Subsequently, the effect of operating parameters such as varying compositions of cow dung (0–100%), molasses concentration (0–100%) and drying time (12–48 h) was investigated. Thus, Central Composite Design using Response Surface Methodology was used to investigate the proximate analysis, calorific value, bulk density and durability of biomass pellets. The experimental results suggested that the addition of cow dung into the base pellet resulted in the increase of volatile matter, ash content, bulk density and durability of the base pellet. As a result, the maximum calorific value of 14.98 MJ/kg, moisture content of 3.37%, volatile matter of 45.49%, ash content of 31.38%, bulk density of 108990 kg/m3 and durability of 95% were obtained. However, optimization of operating parameters was performed to optimize the ash percentage. With the pellet composition of 8.5% (base pellet composition of 90% wheat straw and 10% rice husk), molasses concentration of 50% and drying time of 12 h, 52% reduction in ash content and 2.3% increase in calorific value were obtained at the cost of 38% reduction in the bulk density and insignificant reduction in durability of the produced pellet. Therefore, the use of waste material like cow dung as a binder can be considered as a sustainable approach to improve the physicochemical properties especially durability of biomass pellets. Thus, it can effectively be used to fulfill the energy and heating requirement of rural areas.
•Utilization of cow dung as binder in pellets composed of wheat straw and rice husk.•Production of pellets with maximum calorific value of 19.13 MJ/kg and 98% durability.•52% reduction of ash content by optimizing the % composition of rice husk.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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