The warmest years since global temperature measurements were first recorded in 1880 have all occurred since 2010, with 2014 to 2022 being the nine warmest years. It goes without saying that climate change is coming and this is a loud cry for an energy transition.
A combination of energy efficiency, electrification and renewables can potentially achieve 70% of the emissions reductions needed to limit the increase in average global temperatures to 1.5 degrees Celsius above pre-industrial levels by 2050.
Hydrogen is expected to contribute 10% of that mitigation. Efficient, cost-effective and safe storage and transport of hydrogen could enable its use in place of fossil fuels. However, there is a catch. The exceptionally low density of hydrogen makes existing storage methods expensive, challenging and inefficient. However, the convergence of nanotechnology and climate technology offers a transformational opportunity to enable the major transition of the global energy system.
Considerations
Analyst McKinsey expects demand for clean hydrogen to rise to 585 million tonnes per year by 2050, in a global climate-neutral scenario. However, effectively storing and transporting the energy carrier poses major challenges. Due to the low density of hydrogen, storage requires high-pressure compression of up to 700 bar, resulting in high energy consumption and expensive equipment.
While liquefaction can offer advantages in terms of hydrogen transport, there is the trade-off of high energy consumption during the process; it is even more energy intensive than storing hydrogen under high pressure.
The extremely challenging nature of dealing with hydrogen raises questions about realizing its potential while prioritizing environmental concerns. The key, therefore, is to look for better alternatives where traditional methods fall short.
Transformative forces
A new approach at the atomic level could be the key to advancing the hydrogen economy.
Findings in reticular chemistry – a scientific discipline originally founded by Professor Omar Yaghi that involves linking molecular building units into extended two- and three-dimensional ordered structures using strong bonds – offer promising solutions to address the challenges that hinder efficient storage and transport of hydrogen.
What if it is possible to store and transport hydrogen in a solid state, and ‘adsorb’ it – transferring molecules from a liquid to a solid surface – in specially designed nanomaterials?
There are several unique properties that make nanomaterials, especially MOFs, suitable for hydrogen storage. MOFs are materials designed with atomic precision and characterized by tunable properties that can be tailored by varying the metal ions and organic linkers used in their synthesis. This versatility allows MOFs to be designed to provide customized functionality in terms of specific pore sizes, shapes, and surface characteristics. There lies the potential to overcome many limitations of traditional hydrogen storage methods. In fact, the use of MOFs in hydrogen storage has been recognized by several government agencies and initiatives.
Simply put, hydrogen storage using MOFs can be viewed as combining organic molecules with metal atoms to form a nanoscale crystal structure. Highly porous MOFs can adsorb and retain hydrogen molecules, similar to how a sponge absorbs water. MOFs, with their lattice framework made of metal ions, or clusters coordinated with organic ligands, contain microscopic unfilled regions within their structure. These “cavities” or “pores” allow hydrogen gas molecules to penetrate and stick to the surfaces of the MOFs. The hydrogen gas is then adsorbed onto the empty surfaces.
This unique, hollow, cage-like structure allows MOFs to exhibit exceptionally large surface areas that can be optimized with atomic precision to attract hydrogen molecules. Other classes of reticular materials, such as covalent organic frameworks and hydrogen-bonded organic frameworks, have similar potential to achieve high hydrogen storage density at low pressure.
Energy savings
An ideal hydrogen storage solution should allow high-density hydrogen molecules to be stored without consuming much energy during the charging phase, while also allowing the release of stored hydrogen with minimal energy consumption. The charging rate must be high enough to allow fast refueling and the discharging rate must be high enough to meet the requirements of fuel cells or other downstream processes. Reticular chemistry provides precise control over the composition and properties of nanoscale cavities in new materials and this facilitates the design of materials that can attract hydrogen molecules into cavities without excessive binding, allowing them to be released with minimal energy when necessary.
This approach deviates from traditional high-pressure storage methods by drawing hydrogen in and holding it at low pressure, using reticular materials. The materials attract hydrogen molecules into nanoscale cavities and hold them through bonding, allowing stored hydrogen, even in large quantities, to be efficiently released on demand.
With MOFs it is possible to achieve high storage densities at ambient temperatures and pressures as low as 20 bar. The new technology thus enables high hydrogen storage density without the need for liquefaction or high-pressure tanks. This energy-efficient solution also reduces operating costs compared to high-pressure hydrogen tanks, which, as simulations have shown, can add annual additional energy costs of up to $12,000 to operate a fuel cell transit bus.
Net-zero
Facilitating the hydrogen economy is indispensable to combating climate change. Leveraging decades of discoveries and advances in reticular chemistry has enabled the development of new materials with atomic precision to address the complex properties of hydrogen molecules. By mitigating the challenges associated with the practicalities of hydrogen storage and transportation, the phase-out of fossil fuels becomes more feasible. That is, CO2 emissions can be significantly reduced, making the goal of net-zero emissions less of a distant dream.
About the author: Samer Taha, CEO and co-founder of H2MOF and executive chairman of Revonence, a private equity holding group, has more than 20 years of experience in R&D, technology commercialization and entrepreneurship in information and communications technology (ICT) and nanotechnology. He has founded and led two IT startups, delivering more than $200 million in IT projects.
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