Jianwei Ren

Microwave-assisted modulated synthesis of zirconium-based metal–organic framework (Zr-MOF) for hydrogen storage applications

Abstract Zirconium-based metal–organic framework (Zr-MOF) was synthesized using a microwave-assisted modulated method in a short reaction time of 5 min. The Zr-MOF material was highly crystalline with well-defined octahedral shaped crystals, and it exhibited comparable hydrogen storage capacity to Zr-MOF of similar specific surface area synthesized using conventional methods with much longer synthesis time.

Thermal treatment induced transition from Zn3(OH)2(BDC)2 (MOF-69c) to Zn4O(BDC)3 (MOF-5)

Abstract A simple thermal treatment induced transition from Zn3(OH)2(BDC)2 (MOF-69c) to Zn4O(BDC)3 (MOF-5) is reported. Phase crystallinity, pore characteristics and hydrogen storage capacities of the resulting crystals were investigated. It is shown that the structural transition from Zn3(OH)2(BDC)2 (MOF-69c) to Zn4O(BDC)3 (MOF-5) could be induced by simply employing the optimal thermal treatment conditions of 200 °C for 48 h in open air. The resultant relatively lower specific surface area of MOF-5 crystals compared to MOF-69c was in agreement with the increased pore diameter and decreased hydrogen storage capacity at 1 bar and 77 K.

Shaping Porous Materials for Hydrogen Storage Applications: A Review

Development of safe and effective hydrogen storage systems becomes a critical factor for further implementation of fuel cell and hydrogen technologies. Among new approaches aimed at improving the performance of such systems, the concept of porous materials-based adsorptive hydrogen storage is now considered as a long-term solution due to the reversibility, good kinetics and absence of thermal management issues. However, the low packing densities associated with the porous materials such as carbon structure materials, zeolites, metal-organic frameworks lead to the compromised volumetric capacity, potential pipe contaminations and difficulties in handling, when introducing the powdered adsorbents into hydrogen storage systems. Some efforts have been devoted to solve this problem by shaping the porous materials into beads, pellets or monoliths and achieve higher storage densities at more moderate temperatures and pressures. This review will firstly state the essential properties of shaped structures for hydrogen adsorption, and then highlight the recent attributes that potentially can be utilized to shape porous materials into specific configurations for hydrogen storage applications. Later, several testing techniques on structured porous material will be also discussed.

Comparison of MOF-5- and Cr-MOF-derived carbons for hydrogen storage application

AbstractNanoporous carbons which possess high surface areas and narrow pore size distributions have become one of the most important classes of porous materials with potential to be utilized for hydrogen storage. In recent times, several metal–organic frameworks (MOFs) have been shown to be promising precursors for creating nanoporous carbons due to their high surface areas and tunable pore sizes. The pore structure and surface area of the resultant carbon materials can be tuned simply by changing the calcination temperature. In this work, a zinc-based MOF (MOF-5) and a chromium-based MOF (Cr-MOF) were both used as precursors for syntheses of nanoporous carbons by the direct carbonization technique at different temperatures. The resultant carbon nanostructure from MOF-5 possessed higher surface area, higher pore volume and enhanced hydrogen storage capacity as compared to pristine MOF. Meanwhile, the derived carbons from Cr-MOF displayed lower surface areas, pore volumes and hydrogen uptake than the parent MOF due to the formation of chromium oxide and carbide species in the pores of the Cr-MOF-derived carbons.

Metal-Organic Frameworks as Materials for Fuel Cell Technologies

The dwindling reserves of hydrocarbon fuel resources and the associated environmental impact of burning fossil fuels have led to the search for clean and sustainable energy technologies. Hydrogen is widely considered as a promising alternative to fossil-based fuels because it is clean, has high energy content, and it can potentially be derived from water, which is abundantly available. Fuel cells are a key component of the hydrogen energy value chain where their role is to convert the chemical energy of hydrogen into electrical energy. In the hydrogen energy value chain, hydrogen production and storage are critical enabling technologies for fuel cells. The future of the Hydrogen Economy faces significant challenges which must be overcome before its realisation. Therefore, considerable research is currently directed at finding efficient, safe and affordable materials for fuel cells and their enabling technologies. Metal-organic frameworks (MOFs), a class of organic-inorganic hybrid crystalline solids, are promising materials for these technologies due to their many distinct characteristics including a wide structural diversity, low weight, extraordinarily high surface areas, large free volumes, and tunable pore sizes and functionalities. This chapter presents an overview of MOFs as potential materials for fuel cell components i.e. polymer electrolyte membrane and electrocatalysts, and enabling technologies for fuel cells i.e. hydrogen production and storage. Although significant progress in research has been made there are still challenges to overcome for the practical use of MOFs in these technologies.

Utilization of waste tyres pyrolysis oil vapour in the synthesis of Zeolite Templated Carbons (ZTCs) for hydrogen storage application

ABSTRACT In this study, we investigated the potential for use of waste tyre pyrolysis oil vapour as a carbon precursor in the synthesis of zeolite templated carbons (ZTC). With Zeolite 13X as the template, the ZTCs were synthesised using two methods namely: 1-step process which involved the carbonization of gaseous carbon precursor in the zeolite template (in this case, ethylene and pyrolysis oil vapour) and the 2-step synthesis method involved the impregnation of zeolite pores with furfural alcohol prior to carbonization of the gaseous carbon precursor. The replication of the zeolite 13X structural ordering was successful using both methods. The 2-step synthesized ZTCs were found to possess the highest specific surface area (3341 m2 g−1) and also had the highest H2 storage capacity (2.5 wt.%). The study therefore confirmed an additional novel strategy for value-addition of waste tyre pyrolysis by-products.

Preparation of carbon nanofibers/tubes using waste tyres pyrolysis oil and coal fly ash derived catalyst

ABSTRACT In this study, two waste materials namely; coal fly ash (CFA) and waste tyres pyrolysis oil, were successfuly utilized in the synthesis of carbon nanofibers/tubes (CNF/Ts). In addition, Fe-rich CFA magnetic fraction (Mag-CFA) and ethylene gas were also used for comparison purposes. The carbons obtained from CFA were found to be anchored on the surface of the cenosphere and consisted of both CNTs and CNFs, whereas those obtained from Mag-CFA consisted of only multi-walled carbon nanotubes (MWCNTs). The study further showed that the type of carbon precursor and support material played an important role in determining the nanocarbon growth mechanism. The findings from this research have demonstrated that it is possible to utilize waste tyres pyrolysis oil vapor as a substitute for some expensive commercial carbonaceous gases.

A performance evaluation of a microchannel reactor for the production of hydrogen from formic acid for electrochemical energy applications

An experimental evaluation of a microchannel reactor was completed to assess the reactor performance for the catalytic decomposition of vaporised formic acid (FA) for H2 production. Initially, X-ray powder diffraction (XRD), elemental mapping using SEM-EDS and BET surface area measurements were done to characterise the commercial Au/Al2O3 catalyst. The reactor was evaluated using pure (99.99%) and diluted (50/50 vol.%) FA at reactor temperatures of 250–350°C and inlet vapour flow rates of 12–48 mL.min -1 . Satisfactory reactor performance was demonstrated at 350°C as nearequilibrium FA conversion (>98%) was obtained for all flow rates investigated. The best operating point was identified as 350°C and 48 mL.min -1 (pure FA feed) with a H2 yield of 68.7%. At these conditions the reactor performed well in comparison to conventional systems, achieving a H2 production rate of 11.8 NL.gcat -1 .h -1 . This paper therefore highlights important considerations for ongoing design and development of microchannel reactors for the decomposition of FA for H2 production.

Metal–organic frameworks for hydrogen storage

Abstract Over the past decade, hydrogen storage in metal–organic frameworks (MOFs) has received increasing attention worldwide because they possess versatile structures, high surface areas, large free volumes, ultrahigh porosities, and tunable pore geometries and functionalities. This chapter presents an overview of hydrogen storage in MOFs. It first examines synthetic aspects together with the principal methods that have been employed to synthesize MOFs. The chapter then discusses some of the efforts of hydrogen storage in MOFs at cryo- and room temperature, with an emphasis on the factors that affect hydrogen storage and some attempts to enhance hydrogen storage. The chapter also briefly examines the approach of nanoconfinement of chemical hydrides in MOFs.