Artificial Photosynthesis: Hydrogen fuel from manganese oxide
Artificial Photosynthesis: Hydrogen fuel from manganese oxide
author Added by FuelCellsWorks, December 16, 2015

A new artificial photosynthesis method developed at Florida State University (FSU), Tallahassee, Florida (US), uses less material to capture sunlight and produces hydrogen fuel faster. 

Plants use sunlight to convert water and carbon dioxide to carbohydrates and oxygen. The compounds in FSU’s process can do the same but break down water into hydrogen and oxygen — the generated fuel is hydrogen gas.  Other research teams around the world are investigating different approaches to mimicking nature’s photosynthesis process. FSU professor of chemical engineering Jose L Mendoza-Cortes explains what is innovative about his approach: “We found a material that with electricity converts water into oxygen, and it can also absorb sunlight effectively when taking only one layer of it.”

An energy source that sustains itself

Indeed, the new method only uses a single layer of manganese oxide material, potentially making the solar energy it produces less expensive. Furthermore, mirroring nature, the theoretically self-sustaining process does not generate carbon dioxide. 

The novel system uses manganese, oxygen and salt — all Earth-abundant elements. “With some tweaking, like changing the salt, it can also convert water into oxygen. This then can be used to generate hydrogen gas, which can be used as a fuel,” Mendoza-Cortes says. “The promise that it holds, is that it can potentially be cheap and also resistant, and it can be used for real applications.”

Making the process less expensive by only using one layer of manganese oxide was not the researchers goal initially. The experiment at first involved more expensive procedures, but when they scaled back the number of birnessite layers, the device processed light at a speedier rate. Turns out, a less dense cell used the light more efficiently. Less materials, of course, would mean lower manufacturing costs at scale. 

More manganese-oxide-based solar cells in the future?

The expert agrees that his discovery could inspire new approaches to future solar cell designs. “This family of materials can do two things,” he points out. “One is that it absorbs sunlight effectively in the range that it can drive the conversion of water to oxygen and hydrogen. It can also serve as the catalyst for this conversion.”

Solar cells typically do not store energy. In this case, however, the energy is stored in the hydrogen that is produced, which Mendoza-Cortes says can then be used in a fuel cell to generate energy when the sun is not shining. “Since it generates hydrogen fuel and it is a resistant solar cell that is made of abundant materials, perhaps it can be commercially feasible,” the researcher hopes. 

In fact, it is this very potential beyond the laboratory that has this chemical engineer personally most excited about his research breakthrough. “That it can be more than an academic exercise, and perhaps be applicable to real life and could have an impact,” he adds. 

What is next for the FSU researcher and his team in this endeavor? “Investigate and discover more interesting materials and molecules that can help us find new ways to generate energy in a sustainable fashion, so future generation do not struggle when the non-renewable resources run out,” he says.

The study “Birnessite: A Layered Manganese Oxide To Capture Sunlight for Water-Splitting Catalysis,” co-authored by Mendoza-Cortes, is published in the Journal of Physical Chemistry.