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Abstract The energy penalties associated with the liquid amines carbon dioxide absorption are huge which could be minimised by using materials based carbon capture adsorption. A facile one-step approach for the preparation of activated porous carbon spheres through direct carbonization of d -glucose with a novel non-corrosive chemical, potassium acetate for carbon dioxide capture is presented here. The amount of potassium acetate is varied to control the chemical structure, morphology, porosity and textural features. The potassium acetate/ d -glucose impregnation ratio of 3 is optimum condition for obtaining activated porous carbon spheres with high specific surface area (1917 m2 g−1), spherical morphology, and specific pore volume (0.85 cm3 g−1). The activated porous carbon spheres prepared using different glucose to potassium acetate ratios are employed as carbon dioxide adsorbents. Among all, activated porous carbon spheres prepared with the potassium acetate/ d -glucose of 3 registers the best performance and exhibits carbon dioxide adsorption capacities of 1.96 and 6.62 mmol g−1 at 0 °C/0.15 bar and 0 °C/1 bar. It also shows impressive carbon dioxide adsorption at 0 °C/30 bar (20.08 mmol g−1) and 25 °C/30 bar (14.08 mmol g−1). This performance is attributed to highly developed porous structure of the optimized material. Low isosteric heat of adsorption (24.8–23.04 kJ mol−1) means physisorption which suggests lower energy penalties for material regeneration. A non-complicated synthesis and high carbon dioxide capture demonstrate the importance of this work. This synthesis strategy may be utilized to prepare porous carbons from other precursors which could find potential in energy-related applications.

Platinum is the most effective electro-catalyst for oxidation and reduction processes in direct methanol fuel cells (DMFCs). Although platinum and its alloys show desirable electrochemical activities, these catalysts are expensive and make the commercialization of DMFC less attractive. Beside, literature reviews show that tremendous improvements of the activity and stability of non-platinum cathode catalysts have been achieved over the past few years. However, problems including low reaction rates, high over-potentials and low stabilities that remain unsolved particularly for cathode catalyst are discussed in this paper. This paper also describes the various types of non-platinum materials that can potentially substitute for platinum cathode catalysts in DMFC like macrocyclic molecules such as porphyrins and phthalocyanines, transition metal oxides, transition metal sulfides, amorphous transition metal sulfides, and transition metal-based catalysts. Finally, this paper also summarizes the preparation procedure and the performance of various potential cathode catalysts for DMFC operated in acidic and alkaline media as compared with platinum.

Abstract The study on immobilized titania (TiO2) nanoparticles semiconductor on stainless steel mesh for photocatalytic conversion of CO2 and CH4 has been investigated. Properties of commercial and calcinated photocatalysts on mesh surface were characterized using UV–vis spectra, BET, FESEM and XRD. The photoreduction products were identified with FTIR and GC. The process conditions was optimized using experimental design and process optimization tools to determine the maximum desired response via Response Surface Methodology (RSM) in conjunction with central composite rotatable design (CCRD). The experimental parameters were stainless steel mesh size, amount of titania nanoparticles, calcination temperature, UV light power and initial ratios of CO2:CH4:N2 in feed. Calcination of coated titania nanoparticles increased the absorption of UV–vis light while uniform photocatalyst structure commensurate with decreasing agglomeration. The optimal conditions for maximum CO2 conversion of 37.9% were determined as stainless steel mesh size of 140, coated titania nanoparticles on mesh of 4 g, calcination temperature of 600 °C, UV light power of 250 W and 10% of CO2 in feed. Correspondingly, the selectivity of products were 4.7%, 4.3%, 3.9%, 41.4% and 45.7% for ethane, acetic acid, formic acid, methyl acetate and methyl formate, respectively. The kinetic model, based on Langmuir–Hinshelwood, incorporated photocatalytic adsorptive reduction and oxidation reactions over the catalyst surface, and fitted-well with the experimental data.

Abstract Direct methanol fuel cell (DMFC) durability tests were conducted in three different operational modes: continuous operation with constant load (LT1), on–off operation with constant load (LT2) and on–off operation with variable load (LT3). Porous carbon nanofiber (CNF) anode layers were employed in three sets of single passive DMFCs; each membrane electrode assembly (MEA) was run continuously in durability testing for 3000 h. The objective of this study is to investigate the degradation mechanisms in an MEA with a porous CNF anode layer under different modes of operation. The polarization curves of single passive DMFCs before and after durability tests were compared. The degradation of DMFC performance under the cyclic LT1 mode was much more severe than that of LT2 and LT3 operation. The loss of maximum power density after degradation tests was 49.5%, 28.4% and 43.7% for LT1, LT2 and LT3, respectively. TEM, SEM and EDS mapping were used to investigate the causes of degradation. The lower power loss for LT2 was mainly attributed to the reversible degradation caused by poor water discharge, which thus reduced the air supply. Catalyst agglomeration was especially observed in LT1 and LT3 and is related to carbon corrosion due to possible fuel starvation. The loss of active catalyst area was a major cause of performance degradation in LT1 and LT3. In addition to this, the dissolution and migration of Ru catalyst from the anode to cathode was identified and correlated with degraded cell performance. In the DMFC, the carbon nanofiber anode catalyst support exhibited higher performance stability with less catalyst agglomeration than the cathode catalyst support, carbon black. This study helps understand and elucidate the failure mechanism of MEAs, which could thus help to increase the lifetime of DMFCs.

Abstract This paper describes the experimental characterization of a 25 cm2 laboratory scale vanadium redox flow battery (V-RFB). The unit cell performance with respect to voltage, coulombic and energy efficiencies under different performance parameters (current densities, operating temperatures, flow rates, electrolyte concentrations and material properties of 5 cm × 5 cm electrodes) are presented. The cell exhibits different characteristics under different operating parameters; the highest energy efficiency is recorded at c.a. 82%, operating at 308 K, 60 mA cm−2 and 3 cm3 s−1 volumetric flow rate for 250 cm3 electrolytes (each reservoir) of 1.6 mol dm−3 V(III)/V(IV) in 4 mol dm−3 H2SO4. Formation charge of the mixture of vanadium species into single electro-active species at positive and negative electrodes are presented. Estimated time for the electro-active species to complete the formation charge using electrochemical calculation of Faraday’s constant are presented; a discrepancy of 4.5% is found between the theoretical and experimental data using current density of 80 mA cm−2.

Abstract The increase of global energy consumption and the growing demand of fossil fuels as predominant energy resources have greatly improved the advancement of new technologies in hydrocarbon recovery processes. New class of materials, such as nanoparticles has been widely studied in an effort to ensure simpler and more economical oil exploration and production processes, especially in challenging and harsh reservoirs environments. The unique physical and chemical properties of nanomaterials have lead to their application in almost all oil and gas aspects, such as exploration, reservoir characterization, drilling, cementing, production and stimulation, enhanced oil recovery (EOR), refining and processing. This review article presents comprehensive discussion on the most recent development of nanomaterials and their roles in new or enhanced applications in oil and gas industry. Here, the synthetic strategies and functionalization of some of the most common nanomaterials used in oil and gas industry, i.e. metallic and metal oxide nanoparticles, carbon nanotubes and magnetic nanoparticles are summarized. Their applications in different types of oil and gas processes are also discussed. Finally, an outlook on the current challenges and some prospects for the future applications is also highlighted.

Abstract To ensure deeper market penetration, electrolytes of redox flow batteries (RFB) should be based on low-cost and abundant materials. An all-organic system based on acidic aqueous electrolytes is developed, from a study of theoretical calculations, fundamental chemistry to full-cell testing. The selection of organic active materials in relation to their physical and chemical properties (reaction kinetics, electrode potentials and solubilities) is facilitated by density functional theory (DFT) calculations. Based upon the results, this paper proposes 1,3-cyclohexanedione (1,3-dione) and 1,2-benzoquinone-4,5-disulfonic acid (1,2-BQDS), which are highly soluble and exhibit the most negative (~−0.2 V vs. Standard Hydrogen Electrode (SHE)) and the most positive (~0.80 V vs. Standard Hydrogen Electrode (SHE)) electrode potentials, respectively, under acidic conditions, for which the formation of short-lived and unstable radicals is avoided. The proposed molecules involve at least two proton–two-electron-transfers (pH ≤ 2.5) and yields one of the highest cell voltage (ca. 0.9 V) and reasonable energy efficiencies (>70% at 20 mA cm−2) in acidic electrolytes reported to date.

Abstract Due to its unique structure, characteristics, and bio-availability, glycerol transformation into value-added chemicals has been in the spotlight in recent years. This study provides a comprehensive review and critical analysis on catalytic and electro-chemical oxidation of glycerol into commodity chemicals, which have broad applications to the pharmaceutical, polymer, and food industries. Various synthesis methods (e.g. impregnation, sol-immobilization, incipient wetness, and deposition precipitation) for the preparation of the catalysts are discussed. Catalytic performance of mono-, bi-, multi-, and non-metal supported catalysts on carbon black, activated carbon, graphene, single- or multi wall-carbon nano-tubes, layered-double hydroxides, metal oxides, and polymers are evaluated. Among the methods, sol-immobilization is highly commended since fine metal NPs could be homogeneously distributed on the support, reported as an effective factor for controlling the selectivity of the desired product. In particular, the environmentally benign novel polymeric structures, illustrate significant breakthroughs in production of commodity chemicals compared to the conventional materials. Homogeneous oxidation of glycerol by enzymes and microorganisms also displayed acceptable performance particularly in production of DHA, but at the expense of long reaction time. Unlike the homogenous and heterogeneous catalytic processes, electro-chemical oxidation could be tuned for high product selectivity by controlling the nature, composition and structure of the electro-catalyst as well as the electrode potential. Most importantly, combination of electro-chemical oxidation of glycerol with oxygen or water reduction process in full- and electrolysis-cells, respectively could be the ultimate goal in this field. Simultaneous generation of value-added chemicals and electrical energy would have significant economical and environmental merits compared to the conventional processes. The current state-of-the-art of the glycerol oxidation process and recommendations for further research are also included.