Tech

Not noble catalyst for hydrogen production


Chất xúc tác không cao quý để sản xuất hydro

Credit: Advanced Materials (In 2022). DOI: 10.1002 / adma.202207466

Hydrogen is a promising future fuel—especially if produced from water—but the precious metal catalysts needed are rare, expensive, and in short supply. But now, in a recent study published in Advanced MaterialsResearchers from the University of Tsukuba and collaborating partners have developed a catalyst that can overcome the limitations of precious metals.

Hydrogen is a high-energy molecule that could be a renewable fuel in the future, as it only produces water when burned. Unfortunately, most hydrogen today is derived from the combustion of fossil fuels. Hydrogen produced from water is certainly more environmentally sustainable. However, metal catalyst needed to do the job — such as platinum and iridium — are scarce, expensive, and do not perform as well as they should under extreme conditions, and acidic conditions increase energy efficiency. Which metal can be replaced in acidic medium? The solution proposed by Professor Yoshikazu Ito and colleagues is a surprising one: Using multiple non-precious metals at once.

The researchers used high entropy alloy, is a mixture of many elements. While some of these alloys can be used to generate large amounts of hydrogen, others undergo a process known as oxidation (i.e. passivation) which gives some potential. corrosion resistance for alloys. However, as Professor Ito points out, “it is clear that determining which metal to use in proportion is equal to conventional bottom-up experiments – i.e. changing/adding one metal at a time – Our top-down approach not only saves time, but also provides invaluable chemical insights into the mechanism of hydrogen production.”

Their approach involved homogenous mixing of the nine alloying elements, then surface splitting in an acidic medium, and finally applying a voltage to facilitate structural rearrangements. surface to optimize catalyst activity. Experiments and theoretical calculations have identified metals that contribute to Catalytic activity (e.g. iron, chromium, nickel, cobalt and manganese) and the metals that contribute to passivation (e.g. titanium, zirconium, niobium and molybdenum). Outstanding performance of high entropy alloys and anticorrosion proven in real water electrolysis experiments.

The researchers’ work offers new possibilities and new perspectives on replacing extremely scarce precious metals, especially iridium with a worldwide production of just 7 tons per year. With a spike in the use of water electrolytes globally, iridium demand is expected to be 700 kg per gigawatt.

Aimi AH Tajuddin (first author, PhD student) explains: “Under challenging test conditions of the 0.5 mol sulfuric acid electrolyte, some stability had to be sacrificed to maximize maximize activity, and vice versa.

“The catalyst exhibits overvoltages of only hundreds of millivolts at 10 milliamperes/square meter in hydrogen and oxygen evolution reactions. Moreover, its remarkable performance remains stable in electrochemical cycle tests, equivalent to a 3–4 year lifespan in water electrolyzers powered by intermittent renewable energy sources such as solar power.”

This work succeeded in providing a proof of concept for a new, precious metal-free, economically viable hydrogen production method from water using renewable energy. This method costs only a few hundred US dollars per kilogram of catalyst and is suitable for mass production. The researchers’ application of high entropy alloys will allow the production of hydrogenbatteries and other products that require expensive metals.

More information:
Aimi AH Tajuddin et al., high entropic, corrosion resistant, non-precious metal electrode for oxygen evolution in acidic media, Advanced Materials (In 2022). DOI: 10.1002 / adma.202207466

Quote: Non-noble catalyst for hydrogen production (2022, 11 Nov) retrieved 11 Nov 2022 from https://techxplore.com/news/2022-11-non-noble-catalyst-hydrogen -production.html

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