IAHEAM
Indian Association for Hydrogen Energy and Advanced Materials
IAHEAMIndian Association for Hydrogen Energy and Advanced Materials
D. Pukazhselvan
From the recent experiences it is apparent that the energy and climate change issues are more serious than the predictions. India needs to be seriously prepared with a strong action course for meeting a worst phase of energy deficiency which in fact has already started daunting our economic structure. Hydrogen economy is the only option to curb out a balanced system of energy development and environmental protection. However, hydrogen economy can not be readily implemented without fixing the problems associated with hydrogen production and storage, particularly the latter. As a classical option for storing hydrogen, metal hydrides outclassed all the other modes but still most of the metal hydrides either insufficiently and/or poorly ab/desorb under STP conditions or perform well only under impractical conditions. A most promising candidate rising above all the USDOE storage targets is yet to be established and a technical breakthrough is badly required in the area of material development. In fact, there are many breakthrough reports at times, but someway they do not offer wide scale commercial success due to factors such as cost, processing complications, etc. In whatever sense it is, the present understanding in metal hydride technology is too good as compared to how it was a decade ago. Magnesium hydride was identified as the only reversible binary hydride fit for applications if a 6 wt.% (or even up to 7 wt.%. The theoretical capacity of MgH2 is 7.6 wt.%) reversibility requirement should not be compromised in any way. However, as per the thermodynamics of Mg-H system, hydrogen desorption with an equilibrium situation at 1 atm can be achieved only above 300 °C that too with kinetic limitations. The traditional catalysis approaches have seen improvements in kinetics but as long as its thermodynamic backlash remains, the high temperature requirement does not change and any catalytic approaches remain just as a technical curiosity. Researchers have therefore tried to manipulate the reaction route (as for example, incorporation of transition metals (TM) to make systems like A2BHx, A=Mg, B= TM) but it made the reaction too complex and severely claimed the storage capacity.
A perfect combination of theoretical modeling followed by experimental designing of a material usually works out well for exploring new advances in innovative research. Recently, a team of California Institute of Technology modeled Mg-H clusters and shown that MgH2 particles with sizes lesser than 2 nm show remarkable trend of lowering stability due to modifications in thermodynamics. Later, another group from Curtin University of Technology has experimentally shown that the thermodynamic tuning can be achieved even for sizes up to 7 nm. Inspired by these understanding, the research community has further stepped up to restrict the size of MgH2 particles to whatever smallest is possible. The conventional top-down approaches does not work out due to the poorly sticky, wetting nature of Mg/MgH2 system. Thus, attention was turned on to impregnate the Mg/MgH2 particles permanently on the pores of scaffolds whichever is known with smaller pore size, light weight, high pore volume, excellent durability and outstanding thermal stability, etc. In this line, research efforts are underway and lots of interesting results keep coming in. In a step ahead, a team of Lawrence Berkeley National Laboratory has impregnated Mg clusters inside the gas selective polymer called polymethyl metacrylate (PMMA). This polymer does not allow water or moisture content to pass through but will perfectly gives way in for hydrogen. The results were encouraging in a sense that the system is air stable (which is important due to the fact that Mg is hygroscopic), show improved thermodynamic and kinetic features. While such efforts are encouraging, other ways of storing hydrogen with the help of Mg even in excess of 10 wt.% is also demonstrated by researchers, which obviously gives us scope that the hydrogen community is just closer to the required breakthrough. MgB2 can react with hydrogen in the presence of suitable amount of LiH to give a MgH2 + 2LiBH4 product. These are called RHCs (reactive hydride composites). Such reactions can also be made inside the nanoscaffolds which will give far better results. One has to identify the RHCs with the products showing lesser stability so as to pull the reaction reversible. In such line lot of encouraging results are coming in and a breakthrough leading to commercial success seems foreseeable in the future.
While all these developments are too encouraging, a fact we Indians have to notice is that most of these developments occurred outside our country. In order to stay competitive in international arena for sustainable energy development, India has to emerge strongly in innovative energy research. Hydrogen energy is one area which needs immense attention both from the political and scientific community of our country.
(The author obtained PhD in metal hydride research from Banaras Hindu University, Varanasi, India and presently working as a post doctor in Aveiro University, Portugal. The author can be contacted on dpuksel@gmail.com).
Molybdenum disulphide (MoS2) is one of the mostly used inorganic catalysts in industry today and is a promising candidate to replace the expensive platinum catalyst towards photo and electrochemical hydrogen generation from water. In MoS2 only the surface sites are active towards catalysis where as bulk of the material remains mostly inactive like many other inorganic heterogeneous catalysts. The triangular MoS2 units along the surface edges act as the catalytically active groups.
The research groups lead by Jeffrey R. Long and Christopher J. Chang from the University of California Berkeley have reported a molecular analogue for the active site of MoS2 inorganic solid in which a MoS2 unit is stabilised by a pentapyridyl ligand (Science 2012, 335, 698-702). This study was in line with their previous work, in which they had shown a pentapyridine coordinated Mo-oxo complex was electrochemically active in evolving molecular hydrogen from neutral and sea water (Nature 2010, 464, 1329-1333). They have reacted Mo(II) precursor compound with S8 at room temperature to get the new Mo(IV) disulphide complex. Single crystal X-ray analysis proved that Mo-S and S-S have single bond character and MoS2 groups were found to be nearly the same as that of the active sites found on surface of MoS2 inorganic solid catalysts. This homogeneous catalyst is found to be active towards electro-chemical hydrogen generation from acidic organic or aqueous solution. A similar oxo complex did not produce hydrogen at this condition hence emphasizing the importance of disulphide unit.
This un-optimized first generation MoS2 complex itself has hydrogen evolution activity as comparable to that of hydrogenase enzymes. The preparation of molecular analogs of the active species of inorganic solid heterogeneous catalysts is a big leap towards better catalytic materials for photo/electrochemical hydrogen evolution from water. This method provides a higher density of catalytically active metal sites without the inactive bulk material. Moreover By adopting similar strategy, the higher catalytic activity of heterogeneous catalysis can be hybridized with the better scope of optimization of homogeneous catalysis.
Views: Dr. C.V. Suneesh
Hydrogen cars are not only the future, they are here, now. When hydrogen cars become the status quo, the U. S. can lessen its dependence upon foreign oil, achieve lower prices at the fuel pumps and cut down on the greenhouse gases that produce global warming. Unlike many of the hybrid and "green" cars currently on the market, hydrogen fuel can offer the promise of zero emission technology, where the only byproduct from the cars is heat and water vapor. Current fossil-fuel burning vehicles emit all sorts of pollutants such as carbon dioxide, carbon monoxide, nitrous oxide, ozone and microscopic particulate matter. Hybrids and other green cars address these issues to a large extent but only hydrogen cars hold the promise of zero emission of pollutants. The Environmental Protection Agency estimates that fossil-fuel automobiles emit 1 ½ billion tons of greenhouse gases into the atmosphere each year and going to hydrogen fuel based transportation would all but eliminate this. But Hydrogen fuel-cell vehicles, largely forgotten as attention turned to biofuels and batteries, are staging a comeback, Jeff Tollefson investigates that (Nature 464, 1262-1264 (2010) | doi:10.1038/4641262a) it may due to the following reasons. The future of hydrogen fuel-cell vehicles depends on advances in four key areas: First one is hydrogen source, i.e. hydrogen must be derived from carbon-free renewable source, and one idea is by splitting water using electricity from nuclear plants, wind farms or solar panels. The second is infrastructure, the distribution of hydrogen via special pipelines and tankers in to hydrogen refilling stations. But in order to have a network of H2 filling stations, investors must see a sufficient sales volume of H2 cars. For that investors will not pony up the money to either build the cars that will not sell because of the lack of stations, or the stations which will sit there earning zero revenue because there are no cars on the road. That is the government must invest a lot of money and fund--and convince companies to build the cars and rollout the station infrastructure--the entire system for five to ten years. To be specific, the infrastructure investment must cover production facilities to support a huge volume of H2, trucks to transport the H2 to regional stations, tanks to store the H2 at the station, pumps at the station to deliver the H2 to the cars, and all the related safety, measuring, pumping, transport and regulation equipment. The third challenge is to make the fuel cell light, cheap, robust and durable and powerful enough to run engine, lights and air conditioning. The fourth challenge is the fuel tank for storing hydrogen, liquid hydrogen requires insulated tanks at −253 °C. Most companies prefers to compress the hydrogen inside high strength carbon-fibre tanks. If we want to use renewable hydrogen energy for future we must overcome the above barriers by international technology transfer and global investment.
A national level debate competition for school students to create awareness about Hydrogen Energy.
Date: 28th December 2021
Venue: Online Platform
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A National Meet for Young Scholars of Hydrogen Energy and Advanced Materials
Place and Date will be confirmed soon.
