Bacteria and Sunlight Unleash Sustainable Energy Revolution

Scientists at the University of Rochester are revolutionizing the production of clean, renewable energy by harnessing the power of bacteria and nanomaterials to mimic photosynthesis and generate hydrogen fuel.

In response to the global demand for sustainable energy solutions, researchers at the University of Rochester have drawn inspiration from the natural process of photosynthesis. Their groundbreaking project aims to artificially replicate photosynthesis by using bacteria to transfer electrons to a nanocrystal semiconductor photocatalyst, thereby producing clean hydrogen fuel.

A recent study published in the Proceedings of the National Academy of Sciences by Professor Kara Bren and Professor Todd Krauss of the University of Rochester’s Chemistry department unveiled the cost-effective and efficient utilization of Shewanella oneidensis bacteria as a source of electrons for their artificial photosynthesis system.

By combining the remarkable properties of these microorganisms with nanomaterials, the researchers have developed a system that has the potential to revolutionize the production of hydrogen fuel, replacing current methods reliant on fossil fuels. This breakthrough unlocks a powerful source of renewable energy while significantly reducing greenhouse gas emissions.

Bren emphasizes the significance of hydrogen as “an ideal fuel” due to its environmental friendliness and absence of carbon emissions, setting it apart from traditional fossil fuels. Hydrogen, the most abundant element in the universe, can be obtained from various sources such as water, natural gas, and biomass. Unlike fossil fuels, burning hydrogen only results in the emission of water vapor, making it a clean and sustainable alternative. Moreover, hydrogen fuel boasts a high energy density, enabling its usage in diverse applications, including fuel cells, and facilitating both small-scale and large-scale production for various purposes, from individual households to industrial manufacturing.

Overcoming the challenges associated with hydrogen utilization, which mostly involve extracting hydrogen from compounds like hydrocarbons and water, researchers have pursued artificial photosynthesis as a means to extract hydrogen from water. Artificial photosynthesis systems typically consist of a light absorber, a catalyst for fuel production, and a source of electrons. Immersed in water, these systems rely on a light source to energize the absorber, allowing the catalyst to combine electrons from an external source, such as bacteria, with protons from water to generate hydrogen gas.

However, existing systems either depend on fossil fuels during production or lack an efficient electron transfer mechanism. Addressing this limitation, Bren explains, “We want to get hydrogen from water in a light-driven reaction so we have a truly clean fuel—and do so in a way that we don’t use fossil fuels in the process.”

To overcome this obstacle, Krauss and Bren have spent approximately a decade developing an efficient system that combines artificial photosynthesis with semiconductor nanocrystals as light absorbers and catalysts. Their main challenge was identifying an electron source and establishing an efficient electron transfer from the donor to the nanocrystals. Previous systems relied on ascorbic acid (vitamin C) for electron delivery, but this approach was deemed costly. In their study, the researchers found an unlikely electron donor in Shewanella oneidensis, a bacterium initially sourced from upstate New York’s Lake Oneida. This bacterium provides a cost-effective and efficient means of supplying electrons to the system.

While other research groups have explored the combination of bacteria and nanostructures, Bren and Krauss’s system represents a unique approach. Their system employs bacteria as an electron source for a nanocrystal catalyst, contrasting with previous studies that used bacteria to extract electrons from nanocrystals. Under anaerobic conditions (without oxygen), Shewanella oneidensis respires cellular substances, releasing electrons during fuel metabolism. The bacterium can then donate these electrons to an external catalyst, facilitating hydrogen gas production.

Bren envisions a future where individual homes could house vats and underground tanks that utilize sunlight to generate and store small quantities of hydrogen, providing affordable, clean-burning fuel for powering homes and vehicles. Presently, hydrogen-powered trains, buses, and cars rely primarily on hydrogen derived from fossil fuels. However, Bren stresses the necessity of sourcing hydrogen from water using light-driven reactions, without relying on fossil fuels, to truly benefit the environment.

The study received funding from the US Department of Energy.

Frequently Asked Questions (FAQs) about sustainable energy

More about sustainable energy

• University of Rochester News Release
• Proceedings of the National Academy of Sciences Study
• US Department of Energy