Hydrogen is a fantastic energy source, having more energy content than any other fuel by weight. When it is burned with oxygen, it releases no carbon emissions. These properties make it ideal for mobile applications like hydrogen-powered cars. There’s only one problem though: hydrogen is incredibly expensive and challenging to store, a fact that basically cancels out its advantageous properties.
But a new breakthrough reported by scientists at Deakin University in Australia may change all that. The researchers recently described a mechanochemical approach meant to both separate and store gases by grinding boron nitride powder with small stainless-steel balls in a chamber. The process is very energy efficient and generates virtually no emissions.
The rolling balls that press gases into powder
Oil refineries are responsible for roughly 15% of the world’s energy use. In these processing plants, crude oil is separated into various useful components such as methane gas for household use or gasoline and diesel for transportation using a very energy-intensive process called cryogenic distillation.
The alternative proposed by researchers from Deakin’s Institute for Frontier Materials involves grinding boron nitride powder with metal balls inside a sealed chamber into which gases are introduced that need to be separated. As the chamber rotates at increasingly high speeds, the pressure exerted by the balls rolling up and down the powder increases until the threshold for the absorption of a certain gas is met. As the speed is ramped up, the next gas is absorbed, and so on until you have separated out the useful gases you require for a particular application.
According to their study published in Materials Today, this clever process requires only 90% of the energy used by the petroleum industry in its huge refineries. This is such a massive improvement that Dr. Srikanth Mateti, one of the lead authors of the new study, had to repeat this experiment 20 to 30 times before he could believe it himself.
“We were so surprised to see this happen, but each time we kept getting the exact same result, it was a eureka moment,” Dr. Mateti said in a statement.
The researchers added that boron nitride powder can be reused multiple times for the same process without the need for harsh and toxic chemicals, as you typically encounter in petroleum refining. Boron nitride is perfectly safe to keep in your household, for instance.
Besides helping the petrochemical industry reduce its emissions, the same technique could be used to store and safely transport hydrogen. To release the gases for later use, the powder simply needs to be heated at several hundred degrees Celsius.
“The current way of storing hydrogen is in a high-pressure tank, or by cooling the gas down to a liquid form. Both require large amounts of energy, as well as dangerous processes and chemicals,” said Professor Ying (Ian) Chen, IFM’s Chair of Nanotechnology and co-author of the new study.
“We show there’s a mechanochemical alternative, using ball milling to store gas in the nanomaterial at room temperature. It doesn’t require high pressure or low temperatures, so it would offer a much cheaper and safer way to develop things like hydrogen-powered vehicles.”
For now, this technique — which has been three decades in the making — is a proof of concept. The team reported their results based on the separation of 2-3 liters of material, but they are confident the technology can be scaled up to full pilot. Currently, they are waiting for their provisional patent to be approved.
“We need to further validate this method with industry to develop a practical application,” Professor Chen said.
“To move this from the laboratory to a larger industry scale we need to verify that this process is cost saving, more efficient, and quicker than traditional methods of gas separation and storage.”