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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.

Disposing of solid waste and demand of fossil fuel have become the great challenges in the 21st century. Malaysia as one of the top producers of palm oil and wooden furniture in the world is well positioned to take the challenge of the reuses of its enormous output of lignocellulosic biomass such as oil palm trunk, sawdust of rubberwood and sawdust of mixed hardwood generated from palm oil and furniture industries. Before these lignocellulosic biomasses can be used to produce fuel and major chemicals which are normally derived from petroleum, lignocellulosic materials have to be converted to glucose. Hence, it is a need to investigate the conversion efficiency and to determine the optimum conditions for the conversion of lignocellulosic materials to glucose. This present work is aimed to investigate the potential use of oil palm trunk, rubberwood sawdust and mixed hardwood sawdust as an alternative feedstock for lignocellulosic glucose production. This research also served to identify the optimum two-stage concentrated acid hydrolysis condition that can convert these three lignocellulosic biomasses to glucose efficiently. Two stages concentrated sulfuric acid hydrolysis process using different acid concentration and reaction time were performed on those lignocellulosic biomass samples. The optimum results for oil palm trunk, rubberwood and mixed hardwood sawdust were obtained by using 60% acid concentration reacted for 30 min during 1st stage hydrolysis and subsequently followed by another 60 min reaction time with 30% acid concentration during the 2nd stage hydrolysis. The results, showed that oil palm trunk has a higher glucose conversion yield than those of rubberwood sawdust and mixed hardwood sawdust.

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 Green roofs have been proposed for sustainable buildings in many countries with different climatic conditions. A state-of-the-art review of green roofs emphasizing current implementations, technologies, and benefits is presented in this paper. Technical and construction aspects of green roofs are used to classify different systems. Environmental benefits are then discussed mainly by examining measured performances. By reviewing the benefits related to the reduction of building energy consumption, mitigation of urban heat island effect, improvement of air pollution, water management, increase of sound insulation, and ecological preservation, this paper shows how green roofs may contribute to more sustainable buildings and cities. However, an efficient integration of green roofs needs to take into account both the specific climatic conditions and the characteristics of the buildings. Economic considerations related to the life-cycle cost of green roofs are presented together with policies promoting green roofs worldwide. Findings indicate the undeniable environmental benefits of green roofs and their economic feasibility. Likewise, new policies for promoting green roofs show the necessity for incentivizing programs. Future research lines are recommended and the necessity of cross-disciplinary studies is stressed.

Sediment microbial fuel cells (SMFCs) are an innovative, green technology with great potential, and they utilize a voltage drop of redox potential between aerobes and anaerobes to produce electricity and degrade organic wastewater. However, the power performance and degradation rate in SMFCs are limited by the low concentration of dissolved oxygen on the cathode. Therefore, in this study, SMFCs with comb-type cathode electrodes with carbon cloths exposed partly to air and embedded partly in the reactor substrate were designed and operated. They were utilized for enhancing the power density and the effect of three different exposed areas of cathode electrode for improving transfer of oxygen. Results showed that the power density reached 3.77 × 10−2 mW/m2 for 75% of the (MA75) exposed area, which was 1.93 times than that of 50% of the (MA50) exposed area and 6.44 times than that of 0% (i.e., completely immersed; MA0) exposed area. These results indicated that the exposed area of the cathode electrode had a positive effect on the power performance of SMFCs and would reduce the impedance of the cathode. These findings would apparently offer useful information on the feasibility of SMFCs for wastewater treatment applications in the future.

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.

Hydrogen is a strong candidate as an alternative fuel and energy carrier which could address problems of environmental pollution, emissions, and geo-political tensions. The aim of this paper is to compare the performance of hydrogen fuel with other fuels and to investigate the power and performance penalty when adding different fractions of hydrogen fuel to the other fuels. A one-dimensional model is developed for an engine with hydrogen and gasoline–hydrogen and methane–hydrogen blends. These models have been calibrated and validated against experimental works and the findings of previous studies. The validation of the pressure trace and the torque showed the predictive capability of the model. Furthermore, the penalty and benefits from hydrogen enrichment were clarified. It was shown that adding small controllable mass factions of hydrogen (<10%) to gasoline enhances the burning velocity and combustion process in the low speed range. However, a small reduction in the output power (<6%) was documented. Adding hydrogen to methane showed greater advantages due to the extremely low burning velocity of methane. The benefits of hydrogen addition are considerably stronger than the limitations. Methane–hydrogen blend seemed more attractive than gasoline–hydrogen blends. It can be seen that the developed simulation codes are powerful tools for the H2ICE community.