This latest breakthrough may enable a new approach to renewable energy, using solar energy to convert water (H2O) to hydrogen (H2) during the day and hydrogen back to water at night while providing electrical power.
Similar to a battery, a fuel cell provides stored energy. A proton-exchange membrane fuel cell (PEMFC) gets its energy from the chemical reaction of stored hydrogen and oxygen from the air. These gases combine inside the fuel cell to provide electrical power while emitting only water without carbon dioxide, making this fuel cell environmentally friendly. The PEMFC technology holds great promise as a clean alternative to the internal combustion engine of cars, which emits greenhouse gases and pollutants.
Nonetheless, several hurdles must be surmounted before this fuel-cell technology can be widely adopted. A major issue is that the chemical reaction of reducing oxygen to form water is very sluggish, requiring a huge amount of expensive platinum to kick start the reaction and keep it going. In addition, while the produced water vapor is far better than carbon emissions, its presence at the reaction site would stop the reaction and therefore must be transported away quickly for the reaction to continue.
Led by Yu Huang, a professor of materials science and engineering at UCLA Samueli School of Engineering and corresponding author of the study, the Huang Group was able to overcome several major obstacles to meet DOE requirements. First, the team dramatically accelerated the chemical reaction, greatly reducing the amount of costly platinum needed. In addition, the researchers found a way to quickly expel excess water from the reaction site.
According to the study’s first author, Zipeng Zhao, a postdoctoral fellow in Huang’s group, the key was shaping the nanoscale details of the carbon-support surface to achieve the perfect ratio of the oxygen inflow to match the outflow of water byproduct to maximize the reaction rate.
“Atomically speaking, this is sort of like designing freeway on-ramps and off-ramps for the ideal flow of traffic,” Huang said. “For the ideal fuel cell, we need our incoming traffic of hydrogen and oxygen to merge, and then following their reaction to produce electricity, we need to push the water out as fast as we can. We accomplished this by building upon our previous work and focusing on the overall microenvironment where the reaction takes place. The result is outstanding at an efficiency level where industry can now start to explore adopting this technology.”
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