Andrew Bocarsly, a professor of chemistry at Princeton and a startup company called Liquid Light, Inc. have collaborated on a system that represents a grand leap in solar fuels research – creating formic acid, a potential fuel source, from carbon dioxide, water, and sunlight.

Bocarsly and collaborators used a commercial solar panel to power the conversion of CO2 and water to formic acid, according to a study published in June in the Journal of CO2 Utilization. The process took place inside an electrochemical cell, and used an Iridium-based electrocatalyst. The team achieves a Faradaic yield of ~67% and an overall conversion efficiency of ~1.8%, twice that of natural photosynthesis.

“While the results in themselves are impressive for a liquid carbon-based solar fuel, the dialogue Bocarsly opens up about how to determine efficiencies is enlightening itself,” says Amanda Smeigh, SOFI’s program manager, and expert in solar cells and solar fuels.

“The authors go through multiple ‘efficiency’ calculations and present a novel one that ratios energy output to energy input. This allows them to consider the energy density of their product versus the energy used to make it. From this we can see that if more energy goes into the system than one can get out, the process is not sustainable.”

Smeigh says the important take home message from Bocarsly’s study is that for a system to be practical, and ultimately commercializable, it must exceed the efficiency of natural photosynthesis. With his system, Bocarsly delivers.

This system represents not only a major advance in solar fuels technology, but also a promising form of renewable energy that utilizes waste CO2 to create a clean fuel.