Water splitting has long been hailed as a promising path to clean hydrogen fuel. But while the process looks elegant on paper, it turns out to be far less efficient in practice, demanding significantly more energy than theory predicts. Now, scientists at Northwestern University have discovered a surprising culprit behind this energy gap.
“When you split water, two half-reactions occur,” said Northwestern’s Franz Geiger, who led the study. The half-reaction that produces oxygen is really difficult to perform because everything has to be aligned just right. It ends up taking more energy than theoretically calculated. If you do the math, it should require 1.23 volts. But, in reality, it requires more like 1.5 or 1.6 volts.”
“Providing that extra voltage costs money, and that’s why water splitting hasn’t been implemented at a large scale. By designing new catalysts that make water flipping easier, we could make water splitting more practical and cost-effective.”
The study reveals this molecular acrobatics as a key barrier to oxygen evolution, a critical half-reaction in water splitting. Even more importantly, the researchers found that adjusting the pH of water can make the flipping easier — opening new avenues to optimize the reaction and lower the cost of clean hydrogen fuel.
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