How to improve solid oxide fuel cells

Researchers from Washington State University (WSU) have determined a key step in improving solid oxide fuel cells (SOFCs) — a promising clean energy technology that has so far struggled to gain wide acceptance in the marketplace.

Fuel cells convert the chemical energy in fuels directly into electrical energy. Like batteries, they have an anode, cathode and electrolyte and create electricity. Yet while they are about four times more efficient than combustion engines, as they are based on electrochemical reactions, researchers continue to struggle with making them cheaply and efficiently enough to compete with traditional power generation sources.

An SOFC is made of solid materials, and the electricity is created by oxygen ions travelling through the fuel cell. Unlike other types of fuel cells, SOFCs don’t require the use of expensive metals, like platinum, and can work with a large variety of fuels, such as gasoline or diesel fuel. When gasoline is used, however, a carbon-based material tends to build up in the fuel cell and stop the conversion reaction. Other chemicals, such as sulfur, can poison and stop the reactions.

Investigating the process that stops the reactions, the researchers found that problems most often occur at a place on the anode’s surface, called the triple-phase boundary, where the anode connects with the electrolyte and fuel. The team determined that the presence of an electric field at this boundary can prevent failures and improve the system’s performance. They also studied similar issues in solid oxide electrolysis cells (SOECs), which are like fuel cells that run in reverse to convert carbon dioxide and water to transportation fuel precursors.

According to project leader Jean-Sabin McEwen, the work provides guidance that industry can eventually use to reduce material build-up and poisoning, as well as improve performance of SOFCs and SOECs. The study has been published in the Journal of Physical Chemistry C.