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CHEMISTS at Brookhaven National Laboratory, US, have developed a catalyst based on soya beans and molybdenum to produce hydrogen from water.

The Brookhaven team has been working on a process to mimic photosynthesis in plants, effectively taking the products of hydrocarbon fuel combustion, water and carbon dioxide, back into fuels. An important step of this process is splitting water to produce hydrogen, but the most effective catalyst found so far is platinum, which is prohibitively expensive. The researchers, led by chemist Wei-Fu Chen, say that their new catalyst is not only stable, low-cost and made partly from a renewable resource, but it is the best-performing catalyst yet made that does not contain a noble metal.

Chen and his team had been experimenting with the use of molybdenum paired with carbon, along with nitrogen to help combat the acidic environment in the electrolysis cells. On an internship, highschool students and sisters Shilpa and Shweta Iyer were set a task to find cheap, readily-available sources of carbon and nitrogen. The Iyers hit upon soya beans, as their high protein content means they contain a high proportion of nitrogen.

The catalyst is made by first grinding dried soya beans into a powder and mixing it with ammonium molybdate in water. This mixture was then dried and heated in an inert argon atmosphere.

“A subsequent high temperature treatment (carburisation) induced a reaction between molybdenum and the carbon and nitrogen components of the soybeans to produce molybdenum carbides and molybdenum nitrides. The process is simple, economical, and environmentally friendly,” says Chen.

Neither molybdenum carbide or molybdenum nitride is effective alone as a catalyst in electrolysis cells to split water. The former is unstable, while the later is corrosion resistant but inefficient. A nanostructured combination of the two, however, remained efficient and stable after 500 hours of testing.

The researchers also tested the ‘MoSoy’ catalyst anchored on graphene sheets, which increased its efficiency still further, beating the efficiency of pure platinum. While it is still not as effective as commercially-available platinum catalysts, the team says that it will carry out further studies to better understand the interaction between MoSoy and the graphene substrate to improve its catalytic performance.

“The preparation of the MoSoy catalyst is simple and can be easily scaled up. Its long-term durability and ultra-low capital cost satisfy the prerequisites for its application in the construction of large-scale devices. These findings thus open up new prospects for combining inexpensive biomass and transition metals…to produce catalysts for electro-catalytic reactions,” the researchers say.

Energy and Environmental Science DOI: 10.1039/C3EE40596F