New Device Creates Hydrogen Fuel from Sunlight and Sewage

Sewage and sunlight may not seem like a good combination. For one research team, though, this is the perfect matchup. Scientists have discovered a way to use sunlight and wastewater in order to create hydrogen gas. The findings could be a step forward to providing a sustainable energy source while improving wastewater treatment.

Either a photoelectrochemical cell (PEC) device or microbial fuel cell (MFC) device can be used alone to produce hydrogen gas. Both require a small addition voltage to do so, though; they need it in order to overcome the thermodynamic energy barrier for proton reduction in hydrogen gas. The need to add this additional electric power element adds significantly to both the cost and complication of these types of energy conversion devices. That's why scientists decided to find another way in order to make hydrogen gas.

In this case, the researchers created a hybrid device that combines a MFC and PEC. In the MFC component, bacteria degrade organic matter in the wastewater, generating electricity in the process. This electricity is then delivered to the PEC component in order to assist the solar-powered splitting of water that generates hydrogen and oxygen.

In fact, when fed with wastewater and illuminated in a solar simulator, the PEC-MFC device showed continuous production of hydrogen gas at an average rate of .05 m^3/day. At the same time, the turbid black wastewater became clearer. In addition, the soluble chemical oxygen demand, which is a measure of the amount of organic compounds in water, declined by 67 percent over 48 hours.

That's not all, either. The researchers are planning to scale up their laboratory device in order to make a larger 40-liter prototype continuously fed with municipal wastewater. They then plan to test the device on a wastewater treatment plant.

"The MFC will be integrated with the existing pipelines of the plant for continuous wastewater feeding, and the PEC will be set up outdoors to receive natural solar illumination," said Fang Qian, one of the researchers, in a news release.

The findings are published in the journal ACS Nano.