Clean hydrogen generation and storage strategies via CO2 utilization into chemicals and fuels: A review

Hydrogen becomes one of the most clean energy sources. The major issues on hydrogen are lack of practical clean and high‐temperature processes and possible practical storage of clean hydrogen. An energy intensive of clean hydrogen storage via chemical and liquid fuel production route is the current demand. This article reviewed the most recent research for hydrogen (H₂) production by using several methods, such as thermochemical process, thermal decomposition, biological approaches, electrolysis, and photocatalytic method. H₂ storage types, including physical and chemical approaches, were also reviewed. The produced H₂ was stored as valuable chemicals and fuels via CO₂ hydrogenation reaction. Reactor designs are the illustrated number of design ranging from the fixed bed to the continuous stirred tank reactor. Catalyst type, catalytic system, and the related mechanism of CO₂ hydrogenation reaction to form alcohol, alkanes, and carboxylic acid were also discussed in detail.     

TiO2 nanoparticle embedded nitrogen doped electrospun helical carbon nanofiber-carbon nanotube hybrid anode for lithium-ion batteries

TiO₂ nanoparticles decorated nitrogen (N) doped helical carbon nanofiber (CNF)-carbon nanotube (CNT) hybrid material is prepared by low-cost electrospinning technique followed by hydrothermal method. Morphological investigations establish helical structure of CNFs with hierarchical growth of CNTs around CNFs. The hybrid material shows a high specific surface area of 295.17 m² g^?1 with nanoporous structure. X-ray photoelectron spectroscopic studies establish Ti–O–C/Ti–C bond mediated charge transfer channel between TiO₂ nanoparticles and carbon structures with the success of N doping in CNFs. The electrospun hybrid material delivered high reversible charge capacities of 316 mAh g^?1 (100th cycle) and 244 mAh g^?1 (100th cycle) at a current density of 75 mA g^?1 and 186 mA g^?1 respectively. The charge capacities obtained for different applied current densities are higher than the conventional graphitic microporous microbeads anode. Results indicate that the hybrid material reported here shows high performance compare to graphite for LIBs.     

On the design and optimization of hybrid carbon fiber reinforced polymer-steel cable system for cable-stayed bridges

This paper addresses the effective use of carbon fiber reinforced polymeric (CFRP) materials in the cable system. As the span length of cable-stayed bridges increases, several technical challenges become more dominant with traditional material. This paper mainly focuses on improving the aerodynamic performance through implementing CFRP composites in the cable system in combination with steel. In order to maximize the improvement, a genetic algorithm (GA)-based optimization procedure is developed to optimize the distribution of CFRP and steel. A numerical example is presented and the results suggest the typical composition of an optimized CFRP-steel cable system for long-span cable-stayed bridges.     

On the prediction of solubility of alkane in carbon dioxide using the LSSVM algorithm

The increasing global energy demand and declination of oil reservoir in recent years cause the researchers attention focus on the enhancement of oil recovery approaches. One of the extensive applicable methods for enhancement of oil recovery, which has great efficiency and environmental benefits, is carbon dioxide injection. The CO₂ injection has various effects on the reservoir fluid, which causes enhancement of recovery. One of these effects is extraction of lighter components of crude oil, which straightly depends on solubility of hydrocarbons in carbon dioxide. In order to better understand of this parameter, in this study, Least squares support vector machine (LSSVM) algorithm was developed as a novel predictive tool to estimate solubility of alkane in CO₂ as function of carbon number of alkane, carbon dioxide density, pressure, and temperature. The predicting model outputs were compared with the extracted experimental solubility from literature statistically and graphically. The comparison showed the great ability and high accuracy of developed model in prediction of solubility.     

Adsorption and inhibition behavior of a novel Schiff base on carbon steel corrosion in acid media

In this study, the inhibition effect of 2,2′-(heptane-1,7-diylbis(azanylylidene)bis-(methanylylidene))diphenol (HAMD) on carbon steel corrosion in 0.5 mol L⁻¹ H₂SO₄ solution was studied. Weight loss and electrochemical techniques such as open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to inspect the efficiency of HAMD as corrosion inhibitor. Scanning electron microscopy (SEM) and energy dispersion X-ray (EDAX) were used to characterize the steel surface. Polarization measurements indicated that, the studied inhibitor acts as mixed-type inhibitor. The adsorption of HAMD molecules on the carbon steel surface obeys Langmuir adsorption isotherm.     

A systematic investigation into a novel method for preparing carbon fibre–carbon nanotube hybrid structures

By electrospraying solvent dispersed carbon nanotubes (CNTs) with a binder onto carbon fibre (CF), hybrid structures, with an end aim to improve interfacial bonding in composites, were formed. The electrospray parameters controlling the modification of the CNT morphologies were studied. High-speed camera observations found applied voltage was critical for determining spray mode development. Electric field simulations revealed a concentrated electric field region around each fibre. Both voltage and distance played an important role in determining the CNT morphology by mediating anchoring strength and electric field force. The forming mechanism investigation of different surface morphologies suggested that binder with appropriate wetness gives freedom to the CNTs, allowing them to orientate radially from the CF surface. Linear density (LD) measurements and thermogravimetric analysis revealed that a 10 min coating increased the LD of a single CF filament by up to 31.7% while a 1 h treatment increased fibre bundle mass by 1%.     

Interlaminar fracture of CF/EP composite containing a dual-component microencapsulated self-healant

We present an experimental study of the self-healing ability of carbon fibre/epoxy (CF/EP) composite laminates with microencapsulated epoxy and its hardener (mercaptan) as a healing agent. Epoxy- and hardener-loaded microcapsules (average size large: 123 μm; small: 65 μm) were prepared by in situ polymerisation in an oil-in-water emulsion and were dry-dispersed at the ratio 1:1 on the surface of unidirectional carbon fabric layer. The CF/EP laminates were fabricated using a vacuum-assisted resin infusion (VARI) process. Width-tapered double cantilever beam (WTDCB) specimens were used to measure mode-I interlaminar fracture toughness of the CF/EP composites with a pre-crack in the centre plane where the microcapsules were placed. Incorporation of the dual-component healant stored in the fragile microcapsules provided the laminates with healing capability on delamination damage by recovering as much as 80% of its fracture toughness. It was also observed that the recovery of fracture toughness was directly correlated with the amount of healant covering the fracture plane, with the highest healing efficiency obtained for the laminate with large capsules.     

Detection of occupancy profile based on carbon dioxide concentration pattern matching

Occupancy is one of major factors influencing indoor microclimate. The aim of this work was to determine the influence of this factor on indoor air quality (IAQ) on the basis of CO₂ concentration measurements and statistical analysis. We wanted to identify periods of time when IAQ was strongly affected by the occupancy described by the given profile. The proposed approach consisted of several stages. The CO₂ concentration was measured and recorded in the form of univariate time series. Then, the relationship between occupancy and internal structure of the time series was disclosed. There were distinguished segments based on sample periodogram. Each segment was associated with a particular occupancy profile. In order to detect how human factor represented by a given occupancy profile influences IAQ we proposed to use pattern matching. In this approach there was examined the similarity between segments of the time series and the pattern of CO₂ variability, which represented a selected occupancy profile. The analysis was performed in time domain using moving time window technique. The similarity was judged based on two types of indexes, namely correlation coefficients and distance measures. It was shown that our approach may be applied to successfully detect a particular occupancy profile. The best performance was achieved when using angular distance as the similarity index. In this case we reached 82% true positive and 22% false positive detections. The proposed method may be applied in diagnostics problems to reveal sources of indoor air quality problems.     

Photocatalytic degradation of organic dye using titanium dioxide modified with metal and non-metal deposition

In this study, photocatalytic degradation of methyl orange (MO) as an example of organic dye was investigated using different wt% Pd-loaded and N-doped P-25 titanium dioxide (TiO₂) nanoparticles, as example of metal and nonmetal-doped TiO₂, respectively. The Pd-loaded and N-doped TiO₂ photocatalysts were prepared by post-incorporation method using K₂PdCl₄ and urea, respectively, as precursors. A variety of surface analysis techniques were used for characterization of surface and functional group while using ultraviolet/visible (UV–vis) analysis for monitoring photocatalytic degradation of MO. Kinetic parameters were obtained using Langmuir-Hinshelwood model to determine the degradation rate constants. It was found that the metal-loaded titanium dioxide degraded MO in water at a higher rate than did non-metal-loaded titanium dioxide fabricated by using the post-synthesis method. Also, the pure P25-TiO₂ degraded MO more than N-doped TiO₂ because of decreased surface area by particle agglomeration after being made by the post-incorporation method.     

Carbon resistance of xNi/HTASAO5 catalyst for the production of H2 via CO2 reforming of methane

xNi/HTASAO5 catalysts (x = 2.5, 3.3, 4.4, 5.8, 8.2) were prepared for CO₂ reforming of methane. No crystalline nickel species formed on the catalysts with lower nickel content (≤4.4%), and large Ni⁰ crystallite formed on 5.8% (10 nm) and 8.2 wt%Ni/HTASAO5 (17 nm), whereas the surface concentration of Ce³⁺ decreased with Ni loading. The initial conversion of CH₄ increased from 29.5% to 46.9% with Ni loading. The xNi/HTASAO5 (x ≤ 4.4%) performed stably in the reaction due to the presence of dispersed Ni species and high surface Ce³⁺ content without coke formation, however, 5.8% and 8.2 wt%Ni/HTASAO5 exhibited decreased activity with time on stream, because of the formation of large Ni particles with lower surface Ce³⁺, leading to carbon accumulation. Thus, CH₄ conversion stabilized at about 43% and no carbon formed on 4.4 wt%Ni/HTASAO5 with optimum Ni loading.