A neat way to store and purify hydrogen

Hoshimoto’s concept art for the researchers’ new reaction. The lion – boranes and 2-methylquinoline – finds and holds the hydrogen molecules. Credit: Y. Hoshimoto

Hydrogen gas is going to be an increasingly important substance over the next decade, as a means of storing and transporting renewable energy.

But hydrogen itself is hard to store and transport: as a flammable, invisible gas, it could make for dangerous cargo.

And the most common method of making it at the moment produces a lot of greenhouse gas emissions.

New research, published in Science Advances, might have landed on both an easier way to store it – and a cheaper and less carbon-intensive way to make it.

The researchers, at Osaka University in Japan, have found some substances that react with hydrogen, and only hydrogen – so they can store and release the gas with ease.

Currently, most commercial hydrogen is made from steam-reforming natural (methane) gas, producing carbon dioxide and other greenhouse gases in the process.

The hydrogen made by this method is only about 70% pure: it also contains carbon monoxide, carbon dioxide, and trace amounts of other gases, each of which have to be removed individually through laborious, energy-intensive ways.

“Even a small amount of carbon monoxide can hinder hydrogen uptake,” says corresponding author Associate Professor Yoichi Hoshimoto, from Osaka University’s Department of Applied Chemistry.

“Thus, costly purification methods to isolate the hydrogen prior to storage are necessary.”

The Osaka research has found that boron-based compounds called triaryl boranes could catalyse a reaction between hydrogen and another substance called 2-methylquinoline, causing the hydrogen to stick to the 2-methylquinoline.

The shortcut this work takes: carbon dioxide and other greenhouse gases are still released to make crude hydrogen, but it can then be purified more easily. Credit: Y. Hoshimoto

When heated at 200°C for three hours, the 2-methylquinoline released the hydrogen again.

The resulting method is a 99% efficient way to store hydrogen, and releases hydrogen with 99.9% purity.

The reaction: borane-catalysed hydrogenation of 2-methylquinoline. After heating, the hydrogen is released again. Credit: Y. Hoshimoto

This method still produces some carbon emissions in its first stage – unlike electrolysis, which can be a near zero-emissions way of making hydrogen.

But this chemical trick could help boost the industry in its nascency, and provide a neat storage method.

 

Transferred linked: https://cosmosmagazine.com/science/hydrogen-storage-borane/