Final Report Summary - HYCONES (Hydrogen storage in carbon cones)
The HYCONES project has investigated the use of a radically new material, namely carbon cones (CCs), as a practical, inexpensive, lightweight, high capacity H2 storage material capable of storing / releasing H2 in a temperature window well suited for mobile applications. Carbon cones comprise a new form of carbon, fundamentally different from all the so far known carbon structures, which has been produced in industrial quantities during the so-called Kvaerner carbon black and H2 process and is composed of carbon microstructures, which are flat discs and cones (approximately 20 %). The CCs consist of curved graphite sheets, while five different cone angles have been observed, in accordance with the incurrence of one to five pentagons at the cone tips.
Efficient storage and delivery of H2 are key elements of the H2 economy. Generic use of H2 as an energy carrier requires a means to store excess product for later use, to transport stored H2 from the point of production to the point of use, and to charge and discharge H2 to and from the storage container according to need. Two kinds of storage functions with very different requirements are needed for the H2 economy. Systems used for stationary applications can occupy a large area, employ multi-step chemical charging / recharging cycles, operate at high temperature and pressure, and balance slow kinetics with capacity. On the other hand, H2 storage for transportation, must operate within minimum volume and weight specifications, supply enough H2 to enable a approximately 500 km driving range, charge / recharge near ambient temperature, and provide H2 at rates fast enough for fuel cell locomotion of vehicles. The H2 storage requirements for transportation applications are thus far more stringent and difficult to achieve than those for stationary applications.
The operating requirements for efficient on board H2 storage include appropriate thermodynamics (favourable sorption-desorption enthalpies), fast kinetics (quick uptake release), high storage capacity, effective heat transfer, high gravimetric and volumetric densities (light in weight and conservative in space), long cycle lifetime, high mechanical strength and durability, safety during use and acceptable risk under abnormal conditions. The use of tanks in which H2 is stored as compressed gas or cryogenic liquid, fall far short of the mobile targets due to the required tank volume, safety reasons and energy intensity. Solid storage (in metal hydrides, chemical storage materials and nano-structured materials), holds considerable promise for meeting the targets, but fully satisfactory materials have not been identified yet.
HYCONES targets have been pursued through a coherent work plan built around the following R&D objectives:
- material development including purification (in terms of improving the carbon cones content of the as produced mixed material);
- material decoration with metallic nano-particles that can lead to enhanced hydrogen sorption;
- use advanced experimental techniques to characterise the material, study the interaction of CCs (or metal doped CCs) with H2 on an atomic / molecular scale and thus gain fundamental understanding of the store-release process;
- measure accurately H2 sorption / release capacities, kinetics and cycle-lifetime after following standardised protocols;
- use experimental data and advanced ab-initio and semi-empirical computational calculations to (a) establish the cone structures and resolve the mechanisms of H2 uptake and release, including kinetics, and (b) understand the fundamentals of H2 interaction with cones and metal doped analogues and fine tune the sample synthesis process;
- use mesoscopic simulation tools, based on molecular level modelling, to develop a multi-scale predictive simulation tool, which can describe the H2-cones system from atomic to bed scale.
The HYCONES workplan involved six technical workpackages (WPs) reflecting both basic (characterisation, functionalisation and modelling of innovative nano-structured materials such as CCs) and applied (by exploring the possible use of CCs for H2 storage) research aspects. WP1 focused on down-scaling the CB&H process in order to enable the reproduction of carbon cones. WP2 addressed the purification of the as produced sample aiming to remove the carbon discs and soot and thus improve the carbon cone content. Additionally, WP2 has been aiming at the functionalisation of the CC samples via doping with metallic nanoparticles in an attempt to enhance hydrogen sorption capacity. WP3 activities focused on the use of advanced experimental techniques in order to investigate the CCs morphology, the CC structures in an atomistic level and the interactions between H2 and CCs (or metal doped CCs). The fundamental understanding of H2 storage in CCs was assisted by WP4, which focused on the development of multi-scale advanced computational methods with clear predictive power. The H2 sorption / desorption capacities of WP1 and WP2 samples, the pertinent kinetics and cycle-life were determined within the framework of WP5 by using different techniques. Additionally, a lab-scale CC (100 g carbon or doped carbon material) H2 storage system was developed for testing the performance of the optimised material under realistic conditions.
A bench-scale rig for the production of fresh carbon cone samples has been set-up and the proper adjustment of the reaction conditions led to materials with a progressively improved morphology, i.e. from spherical carbon particles to flat and conical structures. Since graphite sheets and amorphous carbon are considered impurities interfering with most of the CCs properties and thus affect the H2 storage capacity and / or kinetics, purification of the raw samples has been a central activity. In this respect, various methods, both physical and chemical, have been explored for the modification / purification of the raw carbon cone samples received from the available inventory and quite encouraging results have been obtained with respect to the improvement of the respective cone content (gram quantities of highly purified material have been generated). An impressively wide range of state-of- the-art and sophisticated methods have been employed for the study of the morphology and the structure of the materials as well as for the elucidation of their interaction with H2 (calorimetry, inelastic neutron scattering, X-ray photoelectron spectroscopy, neutron diffraction with in-situ H2 sorption, temperature programmed desorption, etc.).
The fundamentals of the associated H2 storage mechanisms have been investigated systematically by intense modelling work on the atomistic-molecular mesoscopic scale which has led to significant conclusions about the properties and the performance of CCs. The atomistic-molecular simulations have resulted in the construction module of the HYCONES code, the only currently available routine that generates reliably multilayered cones and disks of any size with correct bonding topology. Significant work has been also made on molecular - mesoscopic simulations based on grand canonical Monte Carlo (GCMC) calculations. A dedicated GCMC code for the prediction of H2 sorption isotherms of single angle CCs for different P-T conditions has been developed for this purpose. Carbon cones have been shown to exhibit superior performance compared to other geometries such as single wall carbon nanotubes and slits; this can be attributed to the cone tip area but also to the unique combination of local curvature and confinement offered by the cone geometry.
The capability of carbon cones to release hydrogen at near room temperature has been verified experimentally by independent methods, implying a certain potential for use in H2 storage applications. The most interesting results were obtained from the measurement of the metal doped CC samples which showed enhanced hydrogen uptake as high as 4.3 %wt at 25 degrees Celsius and 20 bar. Similar uptake values (3.5 - 3.8 %wt at 25 degrees Celsius and relatively low pressures, circa 10 bar) were recorded during systematic serial charging-discharging experiments on a specially designed lab-scale storage system containing 100 g of alloy doped cyclone purified CC sample. The respective measurements also demonstrated the stability of the material upon cycling.
The results obtained during the course of the HYCONES project have received much attention not only from the scientific community but also industries and relevant stakeholders, as also reflected by the extended dissemination activities. HYCONES consortium has established active links and cooperation with several other running European and international projects and hydrogen storage programs (including DoE activities). Moreover, the project partners disseminated widely their results through appropriate channels. A noticeable number of publications and presentations (40 in total) have been realised by the partners.
Efficient storage and delivery of H2 are key elements of the H2 economy. Generic use of H2 as an energy carrier requires a means to store excess product for later use, to transport stored H2 from the point of production to the point of use, and to charge and discharge H2 to and from the storage container according to need. Two kinds of storage functions with very different requirements are needed for the H2 economy. Systems used for stationary applications can occupy a large area, employ multi-step chemical charging / recharging cycles, operate at high temperature and pressure, and balance slow kinetics with capacity. On the other hand, H2 storage for transportation, must operate within minimum volume and weight specifications, supply enough H2 to enable a approximately 500 km driving range, charge / recharge near ambient temperature, and provide H2 at rates fast enough for fuel cell locomotion of vehicles. The H2 storage requirements for transportation applications are thus far more stringent and difficult to achieve than those for stationary applications.
The operating requirements for efficient on board H2 storage include appropriate thermodynamics (favourable sorption-desorption enthalpies), fast kinetics (quick uptake release), high storage capacity, effective heat transfer, high gravimetric and volumetric densities (light in weight and conservative in space), long cycle lifetime, high mechanical strength and durability, safety during use and acceptable risk under abnormal conditions. The use of tanks in which H2 is stored as compressed gas or cryogenic liquid, fall far short of the mobile targets due to the required tank volume, safety reasons and energy intensity. Solid storage (in metal hydrides, chemical storage materials and nano-structured materials), holds considerable promise for meeting the targets, but fully satisfactory materials have not been identified yet.
HYCONES targets have been pursued through a coherent work plan built around the following R&D objectives:
- material development including purification (in terms of improving the carbon cones content of the as produced mixed material);
- material decoration with metallic nano-particles that can lead to enhanced hydrogen sorption;
- use advanced experimental techniques to characterise the material, study the interaction of CCs (or metal doped CCs) with H2 on an atomic / molecular scale and thus gain fundamental understanding of the store-release process;
- measure accurately H2 sorption / release capacities, kinetics and cycle-lifetime after following standardised protocols;
- use experimental data and advanced ab-initio and semi-empirical computational calculations to (a) establish the cone structures and resolve the mechanisms of H2 uptake and release, including kinetics, and (b) understand the fundamentals of H2 interaction with cones and metal doped analogues and fine tune the sample synthesis process;
- use mesoscopic simulation tools, based on molecular level modelling, to develop a multi-scale predictive simulation tool, which can describe the H2-cones system from atomic to bed scale.
The HYCONES workplan involved six technical workpackages (WPs) reflecting both basic (characterisation, functionalisation and modelling of innovative nano-structured materials such as CCs) and applied (by exploring the possible use of CCs for H2 storage) research aspects. WP1 focused on down-scaling the CB&H process in order to enable the reproduction of carbon cones. WP2 addressed the purification of the as produced sample aiming to remove the carbon discs and soot and thus improve the carbon cone content. Additionally, WP2 has been aiming at the functionalisation of the CC samples via doping with metallic nanoparticles in an attempt to enhance hydrogen sorption capacity. WP3 activities focused on the use of advanced experimental techniques in order to investigate the CCs morphology, the CC structures in an atomistic level and the interactions between H2 and CCs (or metal doped CCs). The fundamental understanding of H2 storage in CCs was assisted by WP4, which focused on the development of multi-scale advanced computational methods with clear predictive power. The H2 sorption / desorption capacities of WP1 and WP2 samples, the pertinent kinetics and cycle-life were determined within the framework of WP5 by using different techniques. Additionally, a lab-scale CC (100 g carbon or doped carbon material) H2 storage system was developed for testing the performance of the optimised material under realistic conditions.
A bench-scale rig for the production of fresh carbon cone samples has been set-up and the proper adjustment of the reaction conditions led to materials with a progressively improved morphology, i.e. from spherical carbon particles to flat and conical structures. Since graphite sheets and amorphous carbon are considered impurities interfering with most of the CCs properties and thus affect the H2 storage capacity and / or kinetics, purification of the raw samples has been a central activity. In this respect, various methods, both physical and chemical, have been explored for the modification / purification of the raw carbon cone samples received from the available inventory and quite encouraging results have been obtained with respect to the improvement of the respective cone content (gram quantities of highly purified material have been generated). An impressively wide range of state-of- the-art and sophisticated methods have been employed for the study of the morphology and the structure of the materials as well as for the elucidation of their interaction with H2 (calorimetry, inelastic neutron scattering, X-ray photoelectron spectroscopy, neutron diffraction with in-situ H2 sorption, temperature programmed desorption, etc.).
The fundamentals of the associated H2 storage mechanisms have been investigated systematically by intense modelling work on the atomistic-molecular mesoscopic scale which has led to significant conclusions about the properties and the performance of CCs. The atomistic-molecular simulations have resulted in the construction module of the HYCONES code, the only currently available routine that generates reliably multilayered cones and disks of any size with correct bonding topology. Significant work has been also made on molecular - mesoscopic simulations based on grand canonical Monte Carlo (GCMC) calculations. A dedicated GCMC code for the prediction of H2 sorption isotherms of single angle CCs for different P-T conditions has been developed for this purpose. Carbon cones have been shown to exhibit superior performance compared to other geometries such as single wall carbon nanotubes and slits; this can be attributed to the cone tip area but also to the unique combination of local curvature and confinement offered by the cone geometry.
The capability of carbon cones to release hydrogen at near room temperature has been verified experimentally by independent methods, implying a certain potential for use in H2 storage applications. The most interesting results were obtained from the measurement of the metal doped CC samples which showed enhanced hydrogen uptake as high as 4.3 %wt at 25 degrees Celsius and 20 bar. Similar uptake values (3.5 - 3.8 %wt at 25 degrees Celsius and relatively low pressures, circa 10 bar) were recorded during systematic serial charging-discharging experiments on a specially designed lab-scale storage system containing 100 g of alloy doped cyclone purified CC sample. The respective measurements also demonstrated the stability of the material upon cycling.
The results obtained during the course of the HYCONES project have received much attention not only from the scientific community but also industries and relevant stakeholders, as also reflected by the extended dissemination activities. HYCONES consortium has established active links and cooperation with several other running European and international projects and hydrogen storage programs (including DoE activities). Moreover, the project partners disseminated widely their results through appropriate channels. A noticeable number of publications and presentations (40 in total) have been realised by the partners.
