The study, published in Communications Chemistry, also showed that the same approach could produce hydrogen from other alcohols and from biomass-derived materials including glucose and cellulose. The researchers said the result points to a potentially low-cost route for hydrogen production using abundant elements.
Catalysts are central to many industrial and consumer technologies, but they are often built from metals and compounds arranged in sophisticated structures that can be expensive and difficult to produce. The Kyushu group said it has been working to develop catalysts based on abundant and inexpensive elements with an eye toward sustainability.
"Our research group has long been interested in developing catalysts from abundant and inexpensive elements. This time we turned our eyes toward sustainability and investigated the utility of common metals as catalysts for producing hydrogen gas," said Associate Professor Takahiro Matsumoto of Kyushu University's Faculty of Engineering, who led the study. "Hydrogen is a clean energy carrier because it does not produce carbon dioxide when used. However, most hydrogen today is made from fossil fuels, so we must develop sustainable methods to produce it to have a positive ecological impact."
The researchers initially set out to generate hydrogen from methanol using organometallic iron complexes. Methanol and other alcohols contain hydrogen that can be removed through alcohol dehydrogenation, but that process usually depends on complex catalysts made from rare or costly metals.
During those experiments, the team encountered an unexpected result in a control test. Instead of relying on a complex iron compound, they found that a mixture of methanol, iron ions, and sodium hydroxide could release a large amount of hydrogen when irradiated with UV light.
"In what can only be considered incredible serendipity, we found in one of our control experiments mixing methanol, iron ions, and sodium hydroxide, and then irradiating it with UV light, generated a considerable amount of hydrogen gas," Matsumoto said. "It was hard to believe at first. We validated these findings, experimented further, and confirmed them. We found that the hydrogen production rate was 921 mmol of hydrogen per hour per gram of catalyst. This number is comparable to the best catalysts reported to date."
The team further reported that the same system could produce hydrogen from a wider range of feedstocks, including other alcohols as well as glucose, starch, and cellulose. That flexibility suggests the method may have value beyond methanol-based reactions if its performance can be improved for those additional materials.
The researchers said more work is needed before the chemistry can be developed into practical hydrogen technology. They still do not understand the detailed reaction mechanism, and catalytic activity remains low for several of the other tested substrates.
"One limitation of this study is that we still do not know the reaction mechanism in detail. Additionally, although we observed hydrogen generation from other materials, the catalytic activity for these substrates is still low," Matsumoto said. "Finally, this reaction is so simple that anyone, from elementary school students to curious adults, can reproduce it. I encourage everyone to try it out, and I hope it inspires people to pursue careers in the sciences."
Research Report:Iron ion enables photocatalytic hydrogen evolution from methanol
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