A new electrochemical system that uses biomass-derived lignin to produce hydrogen has been developed by a team from the School of Energy and Chemical Engineering at the Ulsan National Institute of Science and Technology (Ulsan, South Korea; www.unist.ac.kr), led by professor Jungki Ryu.
In conventional technology, hydrogen is produced through the electrolysis of water. However, in this technology, the oxygen-generation reaction is slow and the hydrogen production is inefficient. This is because the electrons that produce the hydrogen come from the oxygen-evolution reaction.
The team uses a molybdenum-based, inexpensive metal catalyst (phosphomolybdic acid) to break down lignin at low temperatures, and extract the electrons to produce hydrogen. The new system moves electrons from lignin along a wire to the electrode where the hydrogen-evolution reaction occurs. This makes it possible to produce hydrogen with less energy than conventional water electrolysis, as there is no need for oxygen reactions. “Our work is also significant, as it presents a new way to replace oxygen-producing reactions in the electrolysis of water,” says Ryu.
Conventional methods require more than 1.5 V, but the new system can produce hydrogen gas at 0.95 V. Additionally, carbon monoxide and vanillin, which are produced via lignin breakdown, are useful in several industrial processes.