Researchers have identified a way to harness the entire spectrum of sunlight and efficiently transform it into hydrogen for fuel. The method involves a single molecule – an air-stable complex called rhodium – that quickly turns solar energy into hydrogen. While most photocatalysts only absorb the sunlight, requiring another molecule to convert that energy into hydrogen, rhodium does all the work itself, which is why it is faster and more effective. That and its ability to absorbs the entire spectrum of light is why the molecule can harness over 50% more solar energy than current solar cells. The research is published in the journal Nature Chemistry.
Claudia Turro, leader of the study and a chemistry professor and director of The Ohio State University Center for Chemical and Biophysical Dynamics, said:
The whole idea is that we can use photons from the sun and transform it into hydrogen. To put it simply, we are saving the energy from sunlight and storing it into chemical bonds so it can be used at a later time.
The finding could lead to a powerful method of making clean alternatives to fuel things like hydrogen-powered vehicles. It could be an additional way for humans to transition away from fossil fuels that contribute to climate change towards environmentally friendly energy sources that do not.
Turro said:
We have to have renewable energy. Just imagine if we could use sunlight for our energy instead of coal or gas or oil, what we could do to address climate change.
To make the system, the team assembled rhodium atoms into a scaffold structure; that way, the molecule bonds have space in between each other, leaving room for sunlight to be “saved.” In this space, a chemical reaction occurs: two photons (elemental particles of sunlight that contain energy) are converted into two electrons. Even slow or sparse photons from low-energy sunlight are captured because the chemical reaction is direct.
Turro said:
What makes it work is that the system is able to put the molecule into an excited state, where it absorbs the photon and is able to store two electrons to make hydrogen. This storing of two electrons in a single molecule derived from two photons, and using them together to make hydrogen, is unprecedented.
There is a catch: the molecule is a scarce and precious metal, so it’s unbelievably expensive. Regardless, the team remains hopeful and is currently working on improving rhodium to produce hydrogen over a long period while also looking into ways to build the catalyst out of less costly materials.
