New Technologies in Hydrogen Energy: Challenges and Solutions

Hydrogen is often regarded as a promising solution for reducing greenhouse gas emissions in the energy sector. However, this potential comes with unique challenges: the high cost of producing green hydrogen, risks of fire and explosion, and complexities in storage and transportation. Can new technologies address these obstacles? Professor Dmitri Bessarabov shares his insights with Serious Science.

How Can Hydrogen Be Used?

Hydrogen has captured the interest of scientists and energy visionaries largely due to its abundance. As the most widespread element in the Universe, hydrogen is a resource that, unlike oil and natural gas, is unlikely to ever be depleted. However, there’s a challenge: pure hydrogen is virtually nonexistent on Earth. To utilize its energy, we must first extract it from more complex molecules.

The most common method of producing hydrogen today is steam methane reforming; however, this process emits greenhouse gases, undermining hydrogen’s potential environmental benefits. A more sustainable alternative is water electrolysis, which splits water into hydrogen and oxygen as its byproducts. Despite its eco-friendliness, this approach faces significant challenges. First, the cost of hydrogen produced through electrolysis is substantially higher than that of less sustainable methods. Second, energy is lost during the conversion process—turning water into hydrogen and then back into usable energy—which raises the question of whether it might be more efficient to use electricity directly, bypassing these additional steps. Nonetheless, water electrolysis becomes viable when there is a surplus of energy, such as at power plants generating excess electricity. In such cases, the surplus energy can be used for electrolysis, producing hydrogen that acts as a storage medium for future energy needs.

How Can This Hydrogen Be Used? Visionaries have proposed several possibilities for hydrogen utilization, such as powering vehicles through internal combustion engines similar to gasoline ones or through fuel cells. However, a major issue with hydrogen-powered internal combustion engines is that hydrogen burns in air rather than pure oxygen, resulting in not only water but also nitrogen oxides, which are greenhouse gases [1].

Fuel cells, on the other hand, operate on a different principle: they generate electricity and heat by combining hydrogen with atmospheric oxygen. The electricity can then be used to power machinery. Fuel cells are significantly more efficient than internal combustion engines, with efficiencies ranging from 40% to 60%, depending on the type [2].

Despite their advantages, fuel cells face challenges, primarily their high cost. This is largely due to their reliance on expensive platinum-group metal catalysts, such as platinum, palladium, and iridium. These metals are critical to hydrogen energy technologies, but their scarcity and high cost pose a barrier to large-scale production. To overcome this, the development of catalysts that maximize the efficient use of these metals will be essential.

Storage and Transportation: A Potential Hazard

Producing pure hydrogen is just one part of the challenge in hydrogen energy; its storage and transportation present significant hurdles as well. At normal temperature and pressure, hydrogen has a very low density of approximately 0.09 kg/m³, making it impractical for storage, transportation, or use in fuel tanks.

Traditional solutions include liquefying hydrogen—by cooling it to −253°C to −259°C and storing it at relatively low pressure—or compressing it to pressures of up to 700 bar. However, even in these states, hydrogen’s density remains low, and both methods are costly and energy-intensive, further complicating its use as a viable energy source.

Moreover, hydrogen poses additional challenges due to its tendency to make metals and alloys brittle over time. Small hydrogen atoms infiltrate the metal structures, weakening them and ultimately causing material failure. Combined with hydrogen’s flammability, this makes transporting and storing it in potentially leaky metal containers or pipelines a significant safety risk.

One alternative is transporting hydrogen in chemically bonded forms—as non-toxic, non-flammable compounds that can be transported over long distances, ideally using existing infrastructure. Liquid organic hydrogen carriers (LOHCs), which can be easily hydrogenated and dehydrogenated, are being developed for this purpose. For example, dibenzyltoluene enables hydrogen storage densities of 6-7%, compared to just 0.5% for gas cylinders. Another promising option is transporting hydrogen in inorganic forms, such as ammonia, which benefits from a well-established production and transportation infrastructure.

Extracting hydrogen from its carriers, however, requires additional energy. Researchers are working to minimize this energy demand by developing selective catalysts, often involving platinum-group metals combined with more affordable metals and additives such as silicon, phosphorus, or sulfur [3].

For liquid organic hydrogen carriers (LOHCs), it is critical to avoid damaging the carrier molecule during dehydrogenation so it can be reused. Therefore, an ideal catalyst must be precise enough to achieve this. Moreover, the development of dual-purpose catalysts capable of facilitating both hydrogenation and dehydrogenation would significantly reduce transportation costs, making this a highly promising area of ongoing research.

Hydrogen vs. Gasoline: Which Is More Efficient?

Advocates of hydrogen-powered vehicles often highlight hydrogen’s energy density, claiming it is three times higher than that of gasoline. But is this claim accurate?

The answer depends on how energy density is measured. Hydrogen’s gravimetric energy density—energy per unit weight—does appear impressive (120 MJ/kg for hydrogen versus 44 MJ/kg for gasoline). However, the story changes when considering volumetric energy density. Due to hydrogen’s low density, even liquid hydrogen’s volumetric energy density is only 8 MJ/L, compared to gasoline’s 32 MJ/L. Hydrogen compressed to 700 bar pressure has an even lower volumetric energy density [4].

These differences make it challenging to directly compare the practicality of gasoline engines, diesel engines, hydrogen engines, and hydrogen fuel cells. Key factors such as fuel storage type, tank volume and mass, as well as the convenience and safety of refueling, all play a significant role in determining hydrogen’s viability as a transportation fuel.

The Future of Hydrogen: Economic Perspectives

Introducing hydrogen energy into everyday life requires not just scientific breakthroughs but also economic feasibility. Storing energy as hydrogen is practical only when electricity is inexpensive and electrolysis processes are efficient.

Cost-effective green hydrogen production is possible at solar power plants in regions with abundant solar radiation, such as South Africa, Chile, or Australia. However, the challenges don’t end there. Hydrogen must be transported and converted back into usable energy, and each stage of this process needs to be economically viable. Achieving this requires continuous technological innovation and substantial research investments to reduce costs and improve efficiency across the hydrogen value chain.

Scientific advancements, however, require significant investment, creating a paradox: investors may be reluctant to fund research in costly technologies that will remain expensive until more funding is secured. Infrastructure development faces a similar chicken-and-egg dilemma. The limited number of hydrogen vehicles on the road makes investments in hydrogen fueling stations appear unwise, yet without a robust network of fueling stations, consumers are unlikely to purchase hydrogen vehicles. Breaking this cycle will demand coordinated efforts from governments, industries, and researchers.

Ultimately, the goal of hydrogen energy is to minimize humanity’s environmental footprint. However, vehicles running on hydrogen produced via steam methane reforming have a carbon footprint comparable to those powered by fossil fuels. Even hydrogen produced via electrolysis can be environmentally harmful if the electricity used comes from fossil-fuel-based power plants. Achieving truly green hydrogen solutions requires not only green hydrogen production but also an eco-friendly supply chain. Whether this is fully achievable remains to be seen.

References

1. Badea N. (2021). Hydrogen as Energy Sources — Basic Concepts. Energies, 14, 5783.

2. O’Hayre, R., Cha, S.-W., Colella, W., Prinz F.B. (2016). Fuel Cell Fundamentals. Wiley, 3rd edition

3. Gemechu, D. N., Mohammed, A.M., Redi, M., Bessarabov, D., Mekonnen, Y.S., & Obodo, K.O. (2023). First principles-based approaches for catalytic activity on the dehydrogenation of liquid organic hydrogen carriers: A review. International Journal of Hydrogen Energy, 48(85), 33186–33206.

4. Zohuri, B. (2019). Hydrogen Energy. Challenges and Solutions for a Cleaner Future. Springer