The flashing turn signal lever common in automobiles is not present on trains. Trains lack a manual handle to turn left or right, in contrast to automobiles. Instead, a switch point system controls a train, allowing for controlled movement in a chosen direction.
Prof. Yong-Tae Kim, Sang-Hoon You. Image Credit: Pohang University of Science and Technology
This manner of operation is similar to how a catalyst works in fuel cells of hydrogen-powered cars to selectively start chemical processes and prevent corrosion.
Researchers at POSTECH have created a selective catalyst that prevents corrosion in fuel cells used in hydrogen-powered cars, under the direction of Professor Yong-Tae Kim (Department of Material Science and Engineering and Graduate Institute of Ferrous and Energy Materials Technology) and Ph.D. candidate Sang-Hoon You (Department of Material Science and Engineering).
The team was able to prevent fuel cell corrosion by adjusting the hydrogen oxidation process to the amount of hydrogen present in the fuel cell. The study was published in the renowned energy journal ACS Energy Letters.
Many elements can affect the durability of fuel cells. One is deterioration, notably in the cathode catalyst, frequently exposed to start-up and shut-down events in cars. For instance, fuel cells made for automobiles naturally go through cycles of start-up and shut-down.
Fuel cells receive a steady supply of highly concentrated hydrogen during normal vehicle operation, but when the car is started or turned off, the concentration of hydrogen briefly decreases.
As a result, an unexpected oxygen reduction process in the anode is started when external air interacts with hydrogen inside the fuel cells. This causes abrupt potential jumps and carbon corrosion in the cathode.
The research team has developed a catalyst (Pt/TiO2) that effectively prevents corrosion in fuel cells used in hydrogen-powered automobiles. The catalyst is composed of platinum (Pt) placed onto titanium dioxide (TiO2).
This electrocatalyst’s effectiveness is due to the strong interaction between titanium dioxide and platinum as well as the material’s capacity to change its surface conductivity in response to hydrogen concentrations nearby.
The concentration of hydrogen in the fuel reduces proportionately when a vehicle abruptly stops or begins. The expansion of titanium dioxide onto platinum due to this drop in hydrogen concentration causes platinum to get buried under the catalyst’s surface.
Due to the poor conductivity of titanium dioxide, the catalyst eventually becomes an insulator as a result of the expansion of titanium dioxide burying the platinum. The catalyst’s inability to transmit electricity is hampered by this insulating effect, avoiding an unintended drop in oxygen that could otherwise end up in abrupt potential changes in the cathode.
On the other hand, the concentration of hydrogen within the automobile stays high during normal driving. Titanium dioxide reduction takes place on the catalyst’s surface at these extreme hydrogen concentration conditions, exposing the highly conductive platinum and promoting hydrogen mobility there. Hydrogen spillover is a phenomenon that improves current flow and speeds up hydrogen oxidation.
To compare the newly created catalyst with traditional catalysts, the study team also ran a simulation test. According to the test results, Pt/TiO2 catalyst fuel cells were three times more durable than conventional fuel cells.
This shows that the team’s usage of a selective oxygen reduction reaction and a hydrogen oxidation reaction dependent on the hydrogen concentration successfully extended the durability of fuel cells.
The standing of Korean hydrogen-fueled automobiles in the next-generation mobility industry could potentially improve if this study can help to address the current durability issues facing fuel cells for hydrogen-powered vehicles.
The Future Material Discovery Program, the Hydrogen Energy Innovative Technology Development Project, and the Mid-career Researcher Program of the National Research Foundation of Korea provided funding for the execution of this study.