The big picture: Most hydrogen production still relies on natural gas. However, a new technique that uses only sunlight and water could allow humanity to move away from using fossil fuels to produce cleaner energy.

Researchers at Shinshu University in Japan have built a novel reactor to manufacture renewable hydrogen fuel directly from sunlight and water. It’s still an early prototype, but the system could eventually provide a way to produce zero-emission fuel cheaply and sustainably.

The reactor is 1,076 sq ft and employs unique photocatalytic panels to split water molecules into hydrogen and oxygen. This conversion leverages a two-step process. First, the reactor extracts oxygen. The second step separates the hydrogen atoms. The device can then siphon off the hydrogen and store it as a clean-burning fuel for powering vehicles, generators, or other machines.

This method differs from today’s “one-step” catalysts that split water into hydrogen and oxygen in one go. Although the traditional method is easier, it is also terribly inefficient because the hydrogen fuel requires refinement using natural gas.

The team initially tested the reactor with UV light, which showed promise. Under actual sunlight, it yielded even better results, with around 50 percent higher solar energy conversion.

The system sounds quite promising. However, there’s a catch. The reactor only converts about one percent of sunlight into hydrogen fuel under standard simulated conditions. That’s an improvement over previous attempts, but it’s still too low for wide-scale adoption. The researchers note that an approximately five percent efficiency is needed to make it commercially viable.

The scientists believe that increasing the reactor scale and developing new, higher-performing photocatalysts is critical. However, achieving viable efficiency will require a broader scientific effort focused on enhancing the photocatalysts.

“The most important aspect to develop is the efficiency of solar-to-chemical energy conversion by photocatalysts,” senior author Kazunari Domen said.

“If it is improved to a practical level, many researchers will work seriously on the development of mass production technology and gas separation processes, as well as large-scale plant construction. This will also change the way many people, including policymakers, think about solar energy conversion, and accelerate the development of infrastructure, laws, and regulations related to solar fuels.”

Despite the remaining technical hurdles, the concept shows great promise. If scientists can refine the catalysts and scale up the reactors, we could be getting our fuel fix from two of the most plentiful resources on Earth rather than finite fossil fuels.

Masthead credit: Philip Graves