Hydrogen could play a pivotal role in transforming the world's energy portfolio to include more renewable sources. This promise, however, has been elusive, mainly because the production of hydrogen from water is difficult, and sustainable catalysts made from inexpensive and earth-abundant elements that can efficiently catalyze the water-splitting reactions are hard to come by.
Scientists at Rutgers Univ. have developed a catalyst that could address these issues and move hydrogen's potential closer to reality.
"Hydrogen has long been expected to play a vital role in our future energy landscape by mitigating, if not completely eliminating, our reliance on fossil fuels," says
The water-splitting reaction, which decomposes water into oxygen, hydrogen, and electrons, can be thought of as two half reactions: the hydrogen-evolution reaction (HER) and the oxygen-evolution reaction (OER). While catalysts have been found to work well for each of these half reactions, it has been difficult to find HER and OER catalysts that work well in the same pH range. Almost all of the best OER catalysts work well only at neutral or basic pH, and most of the HER catalysts function well only in acidic media. And although platinum-based catalysts are known to efficiently catalyze HER almost regardless of pH, their widespread use has been limited by the high cost and scarcity of platinum.
The Rutgers chemists focused on developing HER catalysts composed of inexpensive and earth-abundant elements that can operate in a wide pH range. (They chose the HER catalyst because OER catalysts that work in a wide pH range are relatively rare.) The new catalyst consists of nitrogen-rich carbon nanotubes (CNTs) embedded with cobalt.
To synthesize the catalyst, the scientists heated graphitic carbon nitride that had been functionalized with Co2+ to 700°C in a nitrogen-rich atmosphere, and then treated the hot material with sulfuric acid for 24 hours. They then performed electrochemical experiments in acid, base, and neutral media. These experiments showed that the cobalt-embedded CNTs are among the most active noble-metal-free heterogeneous catalysts for HER in all three pH environments. In addition, their performance was close to that of platinum.
The researchers have filed for a patent on the catalyst technology, which is available for licensing through the
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