Scientists have searched for a clean energy source for tasks such as car propulsion. Hydrogen has promising qualities: Instead of releasing large quantities of carbon dioxide as exhaust, it only releases water vapor and warm air. In addition to car propulsion, hydrogen is used in the process of ammonia production, metal refining, and plastics manufacturing.
Companies including Toyota, Honda, and Hyundai have released hydrogen-based cars, but none were considered popular, with the best-selling being the Toyota Mirai, selling roughly 14,300 units. One reason for this is because of the limited availability of hydrogen fuel in the United States.
A popular method of obtaining hydrogen is steam methane reformation (SMR). However, SMR also produces carbon monoxide and carbon dioxide, giving it similar issues to combustion engines. To combat this issue, a team at Oregon State University College of Science, led by Kyriakos Stylianou, created a photocatalyst, allowing for a cleaner means of producing hydrogen.
A catalyst is a substance that increases the rate of a chemical reaction without undergoing a permanent change, and a photocatalyst is capable of absorbing light to reach a higher energy level and speed up reactions.
This photocatalyst is a crystalline, porous material known as a metal-organic framework (MOF). This is made of positively charged metal ions surrounded by organic molecules, resulting in a porous material, granting millions of possible different properties. There have been nearly 100,000 of these MOFs created to date, and the properties of over half a million have been predicted. This research centered on the MOF BVR-19, which contains a sulfide-to-sulfide bond, resulting in a reactive sulfur species when exposed to light. By not using metal ions, the reaction relies on the organic component, which is a different way of thinking about using MOFs to produce hydrogen previously. This MOF is also synthesized at room temperature spontaneously, meaning there is a strong energy advantage compared to previous methods such as SMR. Other methods to produce hydrogen are known as hydrolysis and may be more environmentally friendly than SMR, though this is dependent on where the energy is sourced from.
This lays the groundwork for future research, though in its current state it cannot be utilized commercially; it costs $5 per kilogram versus $1.50 per kilogram from SMR. Nevertheless, this provides a positive outlook on the future of hydrogen-based energy.
