Research Articles (SAIAMC)

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A new route to control texture of materials: Nanostructured ZnFe2O4 photoelectrodes
(2013) Tahir, Asif Ali; Burch, Henry A.; Wijayantha, K.G. Upul; Pollet, Bruno G.
Studies were conducted to investigate the influence of deposition solution composition (methanol ≤ the deposition solvent ≤ ethanol) on their physical and chemical properties that matters in the aerosol formation and subsequent decomposition during the aerosol assisted chemical vapour deposition (AACVD) of ZnFe2O4 electrodes. The FEGSEM studies found that the change of composition of deposition solution produced a dramatic change in the ZnFe2O4 electrode texture. The ZnFe2O4 electrodes deposited from methanol as well as predominately methanolic solvents had a relatively compact morphology. In contrast, the electrodes deposited from ethanol as well as predominately ethanolic solvents showed highly textured rod-like structure at nanoscale. The change in electrode texture is explained in terms of changes occurred in precursor decomposition pathways from heterogeneous and homogeneous when the composition of deposition solution is systematically varied. The photoelectrochemical (PEC) properties of all ZnFe2O4 electrodes were studied by recording JeV characteristics under AM1.5 illumination and the photocurrent spectra. The textured electrodes exhibited a significantly higher photocurrent compared to their compact counterparts. This is attributed to the improved photogenerated minority carrier collection at the ZnFe2O4/electrolyte interface as the average feature size gradually decreased. The photocurrent density (at 0.25 V vs. Ag/AgCl/3M KCl) increases rapidly when the electrode is deposited from the solvent containing 60% ethanol and above, which is in close agreement with the textural changes taken place in ZnFe2O4 electrodes.
Application of surface-modified metal hydrides for hydrogen separation from gas mixtures containing carbon dioxide and monoxide
(Elsevier, 2013) Lototskyy, Mykhaylo; Modibane, K.D.; Williams, M.; Klochko, Ye.; Linkov, Vladimir; Pollet, Bruno G.
Application of surface-modified MH material for H2 separation using temperature/pressure swing absorption–desorption was studied. The substrate alloy had the following composition LaNi3.55Co0.75Al0.4-Mn0.3, and the surface modification was carried out through fluorination followed by aminosilane functionalization and electroless deposition of Pd. The material was found to have good poisoning tolerance towards surface adsorbates, even for the large (rv1.5 kg) batches. Feasibility of its application for H2 separation from gas mixtures (up to 30% CO2 and 100 ppm CO) was demonstrated by testing of a prototype H2 separation system (rv280 g of MH in two reactors), and H2 separation reactor (0.75 kg of MH). The H2 separation was characterized by stable performances in the duration of 250 absorption/desorption cycles. However, the total process productivity was found to be limited by the sluggish H2 absorption (partial H2 pressure 62.5 bar, temperature below 100 °C). In the presence of CO2 and CO, additional deceleration of H2 absorption was observed at space velocities of the feed gas below 5000 h
Beef-derived mesoporous carbon as highly efficient support for PtRuIr electrocatalysts and their high activity for CO and methanol oxidation
(SACI, 2014) Wang, Hui; Wang, Rongfang; Ji, Shan; Da, Huahua
In this work, a low-cost and nitrogen-containing carbon with mesoporous pores and high surface area was synthesized by carbonizing a natural biomass precursor, i.e. beef. It is found that the prepared material has excellent textural properties such as high specific surface areas and large pore diameters. TEM images showed that the PtRuIr nanoparticles were well dispersed on the surface of carbonized beef (C-Beef). PtRuIr/C-Beef was highly active for methanol electro-oxidation. PtRuIr/C-Beef showed superior catalytic activity to PtRuIr/C, i.e. lower onset potential and higher oxidation current density. Cyclic voltammograms of CO electro-oxidation showed that PtRuIr/C-Beef catalyst was kinetically more active for CO electro-oxidation than PtRuIr deposited on conventional carbon support. The highly porous structure and low cost of carbonized beef can be widely used as support for highly dispersed metal nanoparticles to increase their electrochemical performance as electrocatalysts.
Biomass-derived activated carbon as high-performance non-precious electrocatalyst for oxygen reduction
(Royal Society of Chemistry, 2013) Wang, Keliang; Wang, Hui; Ji, Shan; Feng, Hanqing; Linkov, Vladimir; Wang, Rongfang
A new type of Fe and N doped carbon material is synthesized by pyrolyzing ferric chloride doped egg white (EW) and the proposed synthetic route is easy, green, and low-cost. In addition, the as-prepared sample exhibits a feasible magnetism and comparable oxygen reduction reaction (ORR) activity to commercial Pt/C.
Catalytic cracking of naphtha: The effect of Fe and Cr impregnated ZSM-5 on olefin selectivity
(Springer Nature, 2018) Mohiuddin, Ebrahim; Mdleleni, Masikana M.; Key, David
This study focuses on the modification of ZSM-5 in order to enhance the catalytic cracking of refinery naphtha to produce light olefins. ZSM-5 was metal modified using different loadings (0.5–5 wt%) of Fe and Cr via the impregnation method. The metal modified ZSM-5 samples are compared and the effect of metal loading on the physicochemical properties and catalytic performance is investigated. Fe and Cr modification had an effect on both the physicochemical properties of the catalysts as well as catalytic activity and selectivity. Metal loading caused a decrease in the specific surface area which decreased further with increased metal loading. Fe had a greater effect on the total acidity in particular strong acid sites when compared to Cr. The optimum Fe loading was established which promoted selectivity to olefins, in particular propylene. Fe also had a dominant effect on the P/E ratio of which a remarkable ratio of five was achieved as well as enhanced the stability of the catalyst. Cr was found to be a good promoter for selectivity to BTX products with a two-fold increase observed when compared to Fe-modified catalysts.
Characterization and activity test of commercial Ni/Al2O3, Cu/ZnO/Al2O3 and prepared NieCu/Al2O3 catalysts for hydrogen production from methane and methanol fuels
(Elsevier, 2013) Khzouz, Martin; Wood, Joe; Pollet, Bruno G.; Bujalski, Waldemar
In this study, methane and methanol steam reforming reactions over commercial Ni/Al2O3, commercial Cu/ZnO/Al2O3 and prepared NieCu/Al2O3 catalysts were investigated. Methane and methanol steam reforming reactions catalysts were characterized using various techniques. The results of characterization showed that Cu particles increase the active particle size of Ni (19.3 nm) in NieCu/Al2O3 catalyst with respect to the commercial Ni/ Al2O3 (17.9). On the other hand, Ni improves Cu dispersion in the same catalyst (1.74%) in comparison with commercial Cu/ZnO/Al2O3 (0.21%). A comprehensive comparison between these two fuels is established in terms of reaction conditions, fuel conversion, H2 selectivity, CO2 and CO selectivity. The prepared catalyst showed low selectivity for CO in both fuels and it was more selective to H2, with H2 selectivities of 99% in methane and 89% in methanol reforming reactions. A significant objective is to develop catalysts which can operate at lower temperatures and resist deactivation. Methanol steam reforming is carried out at a much lower temperature than methane steam reforming in prepared and commercial catalyst (275-325 o C). However, methane steam reforming can be carried out at a relatively low temperature on NieCu catalyst (600-650 o C) and at higher temperature in commercial methane reforming catalyst (700-800 o C). Commercial Ni/Al2O3 catalyst resulted in high coke formation (28.3% loss in mass) compared to prepared NieCu/Al2O3 (8.9%) and commercial Cu/ZnO/Al2O3 catalysts (3.5%).
CNx-modified Fe3O4 as Pt nanoparticle support for the oxygen reduction reaction
(Springer, 2013) Wang, Rongfang; Jia, Jingchun; Wang, Hui; Wang, Qizhao; Ji, Shan; Tian, Zhongqun
A novel electrocatalyst support material, nitrogendoped carbon (CNx)-modified Fe3O4 (Fe3O4-CNx), was synthesized through carbonizing a polypyrrole-Fe3O4 hybridized precursor. Subsequently, Fe3O4-CNx-supported Pt (Pt/Fe3O4-CNx) nanocomposites were prepared by reducing Pt precursor in ethylene glycol solution and evaluated for the oxygen reduction reaction (ORR). The Pt/Fe3O4-CNx catalysts were characterized by X-ray diffraction, Raman spectra, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The electrocatalytic activity and stability of the as-prepared electrocatalysts toward ORR were studied by cyclic voltammetry and steady-state polarization measurements. The results showed that Pt/ Fe3O4-CNx catalysts exhibited superior catalytic performance for ORR to the conventional Pt/C and Pt/C-CNx catalysts.
Components for PEM fuel cells: An overview
(Trans Tech Publications, 2010) Sivakumar, Pasupathi; Maiyalagan, Thandavarayan
Fuel cells, as devices for direct conversion of the chemical energy of a fuel into electricity by electrochemical reactions, are among the key enabling technologies for the transition to a hydrogen-based economy. Among the various types of fuel cells, polymer electrolyte membrane fuel cells (PEMFCs) are considered to be at the forefront for commercialization for portable and transportation applications because of their high energy conversion efficiency and low pollutant emission. Cost and durability of PEMFCs are the two major challenges that need to be addressed to facilitate their commercialization. The properties of the membrane electrode assembly (MEA) have a direct impact on both cost and durability of a PEMFC. An overview is presented on the key components of the PEMFC MEA. The success of the MEA and thereby PEMFC technology is believed to depend largely on two key materials: the membrane and the electro-catalyst. These two key materials are directly linked to the major challenges faced in PEMFC, namely, the performance, and cost. Concerted efforts are conducted globally for the past couple of decades to address these challenges. This chapter aims to provide the reader an overview of the major research findings to date on the key components of a PEMFC MEA.
A comprehensive review on hydrogen absorption behaviour of metal alloys prepared through mechanical alloying
(MDPI, 2020) Davids, Moegamat Wafeeq; Somo, Thabang Ronny; Maponya, Thabiso Carol
Hydride-forming alloys are currently considered reliable and suitable hydrogen storage materials because of their relatively high volumetric densities, and reversible H2 absorption/desorption kinetics, with high storage capacity. Nonetheless, their practical use is obstructed by several factors, including deterioration and slow hydrogen absorption/desorption kinetics resulting from the surface chemical action of gas impurities. Lately, common strategies, such as spark plasma sintering, mechanical alloying, melt spinning, surface modification and alloying with other elements have been exploited, in order to overcome kinetic barriers. Through these techniques, improvements in hydriding kinetics has been achieved, however, it is still far from that required in practical application. In this review, we provide a critical overview on the effect of mechanical alloying of various metal hydrides (MHs), ranging from binary hydrides (CaH2, MgH2, etc) to ternary hydrides (examples being Ti-Mn-N and Ca-La-Mg-based systems), that are used in solid-state hydrogen storage, while we also deliver comparative study on how the aforementioned alloy preparation techniques affect H2 absorption/desorption kinetics of different MHs. Comparisons have been made on the resultant material phases attained by mechanical alloying with those of melt spinning and spark plasma sintering techniques.
Control strategy of a fuel-cell power module for electric forklift
(Elsevier, 2021) Radica, Gojmir; Tolj, Ivan; Lototskyy, Mykhaylo V.
Fuel cell-battery hybrid systems for the powertrain, which have the advantage of emissionfree power generation and adapt to material transport and emission reduction, are investigated. Based on the characteristics of the fuel cell system and the characteristics of the electric forklift truck powertrain system, this work defines the design principle of the control strategy to improve overall performance and economy. A simulation platform for fuel cell and electric vehicles has been established. The optimal performance of the fuel cell stack and the battery capacity were defined for the specific application. An energy control strategy was defined for different operating cycles and operating conditions. Model validation involved comparing simulation results with experimental data obtained during VDI60 test protocol. The main parameters that influence the forklift performance were defined and evaluated, such as energy loss, fuel cell operating conditions and different battery charging cycles. The optimal size of the fuel cell stack of 11 kW and the battery of 10 Ah was determined for the specific load profile with the proposed control strategy. The results obtained in this work forms the basis for an in-depth study of the energy management of fuel cell battery drive trains for forklift trucks.
Current status of fuel cell based combined heat and power systems forresidential sector
(Elsevier, 2015) Ellamla, Harikishan R.; Staffell, Iain; Bujlo, Piotr
Combined Heat and Power (CHP) is the sequential or simultaneous generation of multiple forms of usefulenergy, usually electrical and thermal, in a single and integrated system. Implementing CHP systems inthe current energy sector may solve energy shortages, climate change and energy conservation issues.This review paper is divided into six sections: thefirst part defines and classifies the types of fuel cellused in CHP systems; the second part discusses the current status of fuel cell CHP (FC-CHP) around theworld and highlights the benefits and drawbacks of CHP systems; the third part focuses on techniques formodelling CHP systems. The fourth section gives a thorough comparison and discussion of the two mainfuel cell technologies used in FC-CHP (PEMFC and SOFC), characterising their technical performance andrecent developments from the major manufacturers. Thefifth section describes all the main componentsof FC-CHP systems and explains the issues connected with their practical application. The last partsummarises the above, and reflects on micro FC-CHP system technology and its future prospects.
Dehydrogenation of metal hydride reactor-phase change materials coupled with light-duty fuel cell vehicles
(MDPI, 2022) Nyamsi, Serge Nyallang; Tolj, Ivan; Geca, Michał Jan
The popularity of using phase change materials (PCMs) for heat storage and recovery of metal hydrides’ reaction has grown tremendously. However, a fundamental study of the coupling of such a system with a low-temperature PEM (polymer electrolyte membrane) fuel cell is still lacking. This work presents a numerical investigation of the dehydrogenation performance of a metal hydride reactor (MHR)-PCM system coupled with a fuel cell. It is shown that to supply the fuel cell with a constant H2 flow rate, the PCM properties need to be in an optimized range.
Development of FeCux/FeS/Graphite composite electrode materials for iron-based Alkaline batteries
(Electrochemical Science Group, University of Belgrade, 2020) Tawonezvi, Tendai; Bladergroen, Bernard Jan; John, Joe
In an attempt to enhance the electrochemical performance of the iron-based electrode, an iron-core copper-shell nano-structured material was synthesized and incorporated with ferrous sulphide, and graphite additives. An electrically conductive nickel mesh as a current collector, coupled with a low-cost hot-pressing technique, was employed to formulate the electrodes. The ferrous and graphite integrated iron-core copper-shell nano-structured negative electrode was investigated for applications in Fe-based alkaline batteries energy storage. FeCu0.25/15%FeS/5%C composite electrode delivered a specific discharge capacity of 385 mAh g-1 an approximately 71% coulombic efficiency. The nominal specific capacity of the electrode exhibited negligible capacity degradation after 40 cycles. Ex-situ X-ray Diffraction characterisations and scanning electrode microscopy images of both the fresh and the discharged electrode surfaces show that particle arrangement was still intact after 40 cycles, with negligible particle agglomeration compared to the pure iron electrode surface which was marked with massive agglomeration.
The effect of slurry wet mixing time, thermal treatment, and method of electrode preparation on membrane capacitive deionisation performance
(MDPI, 2021) Botha, Ebrahiem; Smith, Nafeesah; Hlabano-Moyo, Bongibethu
Capacitive deionisation (CDI) electrodes with identical composition were prepared using three deposition methods: (1) slurry infiltration by calendering (SIC), (2) ink infiltration dropwise (IID), and (3) ink deposition by spray coating (IDSC). The SIC method clearly showed favourable establishment of an electrode with superior desalination capacity. Desalination results showed that electrodes produced from slurries mixed longer than 30 min displayed a significant reduction in the maximum salt adsorption capacity, due to the agglomeration of carbon black. The electrodes were then thermally treated at 130, 250, and 350 ◦C. Polyvinylidene difluoride (PVDF) decomposition was observed when the electrodes were treated at temperatures higher than 180 ◦C. The electrodes treated at 350 ◦C showed contact angles of θ = 0◦ . The optimised electrodes showed a salt adsorption capacity value of 24.8 mg/g (130 ◦C). All CDI electrodes were analysed using specific surface area by N2 adsorption, contact angle measurements, conductivity by the four-point probe method and salt adsorption/desorption experiments. Selected reagents and CDI electrodes were characterised using thermogravimetric analysis coupled with mass spectrometry (TGA-MS) and differential scanning calorimetry (DSC), as well as scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS).
Effect of the structure of Ni nanoparticles on the electrocatalytic activity of Ni@Pd/C for formic acid oxidation
(Elsevier, 2013) Wang, Rongfang; Wang, Hui; Wang, Xingli; Liao, Shijun; Linkov, Vladimir; Ji, Shan
Ni@Pd/C catalysts were synthesized, using Ni/C with different crystalline structures prepared with various ligands. A series of characterizations were performed by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy. The results indicated the electrocatalysts with amorphous/crystalline (denoted as Nia and Nic) Ni structures decorated with Pd. The formic acid electrocatalytic oxidation results showed that the peak current of Nia@Pd/C was about 1.2 times higher than that of Nic@Pd/C. The good electrochemical performance and stability of Pd-modified amorphous Ni substrate reveals that the core structure plays an important role in the electrocatalytic activity and the change of the structure can improve the activity and stability of electrocatalysts.
Effective hierarchical ZSM-5 catalysts for the cracking of naphtha and waste tire-derived oil to light olefins
(John Wiley and Sons Ltd, 2024) Nqakala, Loyiso; Mohiuddin, Ebrahim; Mpungose, Philani; Mdleleni, Masikana
Hierarchical ZSM-5 zeolite materials with different SiO2/Al2O3 molar ratios in the range of 60–300 were synthesized using soft templating and microemulsion methods to generate zeolite materials with narrow mesopore size distributions. The resulting materials were characterized by X-ray flourescence (XRF), Fourier transform infra-red (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), ammonia temperature programmed desorption (NH3-TPD), thermo-gravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) surface area measurements, and products from the catalytic tests were analyzed by gas chromatography (GC). The XRF analysis determined that the Si/Al ratios for the synthesized ZSM-5 were close to the batch ratios. The XRD and FTIR results revealed that the synthesized samples had crystalline ZSM-5 zeolite structures. The small angle observed from the XRD patterns confirmed the presence of mesopores in the structure of the prepared materials. The SEM results showed that the ZSM-5 synthesized materials had different morphologies and particle sizes, as well as worm-like holes indicating that some macropores with average pore sizes ranging between 68 and 85 nm were successfully generated in these materials. NH3-TPD results showed that the total acidity of the prepared materials decreased with an increase in the Si/Al (SA) ratio following this trend: SA = 71 > 177 > 345. This may be due to the decrease in the aluminum content, which is largely responsible for the formation of acidic sites in zeolites.
Effects of heat treatment on the catalytic activity and methanol tolerance of carbon-supported platinum alloys
(Springer, 2012) Valisi, Andiswa; Maiyalagan, Thandavarayan; Khotseng, Lindiwe; Linkov, Vladimir; Pasupathi, Sivakumar
This work studies the effect of heat treatment of carbon-dispersed platinum and platinum alloys on its methanol tolerance and catalytic activity as gas diffusion electrodes for oxygen reduction reaction (ORR) in acid medium. The catalyst powders were subjected to heat treatments at three different temperatures for a fixed period at controlled atmospheres. Differences in catalyst morphology were characterized using X-ray diffraction, energy dispersive X-ray analysis and transmission electron microscope techniques. The electrochemical characteristics and activity of the electro-catalysts were evaluated for ORR and methanol tolerance using cyclic voltammetry, in the form of gas diffusion electrodes. The optimum heat-treatment temperature is found to be strongly dependent on the individual catalyst. The maximum ORR activity and better methanol tolerance for the oxygen reduction reaction (ORR) was observed in Pt-Fe/C and Pt-Cu/C catalysts subjected to heat treatment at 350 °C.A trend of catalytic activity for oxygen reduction reaction (ORR) was obtained: Pt-Cu/C (350°C)>Pt-Fe/C (350°C) > Pt-Ni/C (350°C) > Pt-Co/C (250°C) > Pt/C (350°C), showing that Pt-Cu/C-type catalysts had a higher catalytic activity with reasonable methanol tolerance.
Electrochemical performance of zinc carbodiimides based porous nanocomposites as supercapacitors
(Elsevier, 2021) Linkov, V; Shen, J; Chen, X
The low energy densities of supercapacitors are generally limited by the used anodes. To develop supercapacitors with high energy densities, metal–organic framework (TRD-ZIF-8) derived honeycomb-like porous zinc carbodiimide (ZnNCN) based nanocomposites (HPZC) surface loaded with graphitized carbon nitride (g-C3N4) are synthesized. After their detailed characterization by means of electron microscopy, spectroscopy and electrochemical techniques, the materials are used to prepare asymmetric supercapacitor cells (HPZC-4//AC ASCs) with HPZC-4 and active carbon as electrodes, which demonstrate power and energy densities as high as 7839 W Kg−1 and 213 Wh Kg−1, respectively. The unique honeycomb-like porous structure of HPZC loaded with a 2D material (g-C3N4) improves charge/mass transport efficiency and reduces ion diffusion resistance, contributing to a specific capacitance of 779 F g−1 at a current density of 3 A g−1.
Enhanced drug loading capacity of polypyrrole nanowire network for confrolled drug release
(Elsevier, 2013) Jiang, Shuhui; Sun, Yanan; Cui, Xin; Huang, Xiang; He, Yuan; Ji, Shan; Shi, Wei; Ge, Dongtao
For a conducting polymer (CP) based drug release system, drug loading is often accomplished by a doping process, in which drug is incorporated into polymer as dopant. Therefore, the drug loading capacity is relatively low and the range of drugs can be loaded is limited. In the present work, a polypyrrole (PPy) nanowire network is prepared by an electrochemical method and it is found that the micro- and nano- gaps among the individual nanowires of the PPy nanowire network can be used as reservoir to store drugs. Therefore, the drug loading capacity is dependent on the volume of these micro- and nano-vacancies, instead of the doping level. The range of loaded drugs also can be theoretically extended to any drugs, instead of only charged dopants. In fact, it is confirmed here that both hydrophilic and lipophilic drugs can be loaded into the micro- and nano-gaps due to the amphilicity of the PPy nanowire network. As a result, both drug loading capacity and the range of drugs can be loaded are significantly improved. After being covered with a protective PPy film, controlled drug release from the prepared system is achieved by electrical stimulation (cyclic voltammetry, CV) and the amount of drug released can be controlled by changing the scan rate of CV and the thickness of the protective PPy film.
Enhanced performance of polybenzimidazole-based high temperature proton exchange membrane fuel cell with gas diffusion electrodes prepared by automatic catalyst spraying under irradiation technique
(Elsevier, 2013) Su, Huaneng; Pasupathi, Sivakumar; Bladergroen, Bernard Jan; Linkov, Vladimir; Pollet, Bruno G.
Gas diffusion electrodes (GDEs) prepared by a novel automatic catalyst spraying under irradiation (ACSUI) technique are investigated for improving the performance of phosphoric acid (PA)-doped polybenzimidazole (PBI) high temperature proton exchange membrane fuel cell (PEMFC). The physical properties of the GDEs are characterized by pore size distribution and scanning electron microscopy (SEM). The electrochemical properties of the membrane electrode assembly (MEA) with the GDEs are evaluated and analyzed by polarization curve, cyclic voltammetry (CV) and electrochemistry impedance spectroscopy (EIS). Effects of PTFE binder content, PA impregnation and heat treatment on the GDEs are investigated to determine the optimum performance of the single cell. At ambient pressure and 160 o C, the maximum power density can reach 0.61 W cm-2, and the current density at 0.6 V is up to 0.38 A cm-2, with H /air and a platinum loading of 0.5 mg cm-2 on both electrodes. The MEA with the GDEs shows good stability for fuel cell operating in a short term durability test.

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