‘Accidental power trip’ leads scientists to discover new way of generating hydrogen

Researchers from the National University of Singapore (NUS) stumbled upon a discovery that could forever revolutionize how we acquire hydrogen from water, according to a press release from the institution published on Thursday.

Light as a trigger

The team was led by Associate Professor Xue Jun Min, Dr Wang Xiaopeng and Dr Vincent Lee Wee Siang from the Department of Materials Science and Engineering under the NUS College of Design and Engineering (NUS CDE). The discovery they made was that light could trigger a new mechanism in a catalytic material used in water electrolysis.

“We discovered that the redox center for electro-catalytic reaction is switched between metal and oxygen, triggered by light,” said Jun Min. “This largely improves the water electrolysis efficiency.”

It all began with an accidental power trip of the ceiling lights in Jun Min’s laboratory almost three years ago. Back then, the ceiling lights in Jun Min’s research lab were normally turned on for 24 hours. When the lights went off due to a power failure, there was an opportunity to observe something that scientists had never witnessed before.

When the researchers returned the next day, they found that the darkness had influenced the performance of a nickel oxyhydroxide-based material in the water electrolysis experiment. It had fallen drastically.

“This drop in performance, nobody has ever noticed it before, because no one has ever done the experiment in the dark,” said Jun Min. “Also, the literature says that such a material shouldn’t be sensitive to light; light should not have any effect on its properties.”

Jun Min and his team knew they had stumbled on something significant, and they embarked on numerous repeated experiments to test out their new theories. They eventually had enough data to publish a paper.

Now, the team is working on new ways to improve industrial processes to generate hydrogen such as making the cells containing water to be transparent, so as to introduce light into the water splitting process.

“This should require less energy in the electrolysis process, and it should be much easier using natural light,” said Jun Min. “More hydrogen can be produced in a shorter amount of time, with less energy consumed.”

Pushing the boundaries

Jun Min added that the best way to develop science is not to keep finding new ways to do what has already been done, but to constantly push the boundaries.

“It’s only through accumulation of new knowledge that we can improve society progressively,” said Jun Min.

This discovery is bound to affect food companies that use hydrogen gas to turn unsaturated oils and fats into saturated ones and the petroleum industry that uses the gas to remove sulphur content from oil.

Hydrogen also has the potential to be used as an eco-friendly fuel as it produces no emissions and is easier to store, making it more reliable than solar-powered batteries.

The paper is published in the Nature journal.

Abstract:

Realizing an efficient electron transfer process in the oxygen evolution reaction by modifying the electronic states around the Fermi level is crucial in developing high-performing and robust electrocatalysts. Typically, electron transfer proceeds solely through either a metal redox chemistry (an adsorbate evolution mechanism (AEM), with metal bands around the Fermi level) or an oxygen redox chemistry (a lattice oxygen oxidation mechanism (LOM), with oxygen bands around the Fermi level), without the concurrent occurrence of both metal and oxygen redox chemistries in the same electron transfer pathway. Here we report an electron transfer mechanism that involves a switchable metal and oxygen redox chemistry in nickel-oxyhydroxide-based materials with light as the trigger. In contrast to the traditional AEM and LOM, the proposed light-triggered coupled oxygen evolution mechanism requires the unit cell to undergo reversible geometric conversion between octahedron (NiO6) and square planar (NiO4) to achieve electronic states (around the Fermi level) with alternative metal and oxygen characters throughout the oxygen evolution process. Utilizing this electron transfer pathway can bypass the potential limiting steps, that is, oxygen–oxygen bonding in AEM and deprotonation in LOM1. As a result, the electrocatalysts that operate through this route show superior activity compared with previously reported electrocatalysts. Thus, it is expected that the proposed light-triggered coupled oxygen evolution mechanism adds a layer of understanding to the oxygen evolution research scene.