A recent collaboration between Oregon State University's College of Engineering, Cornell University, and the Argonne National Laboratory has made significant progress in hydrogen extraction from water.
Researchers employed a range of experimental tools to further illuminate the mechanisms behind an electrochemical catalytic process that promises to be more sustainable and more environmentally friendly than existing methods of drawing hydrogen from natural gas. Their findings are published in the journal Science Advances.
Drawing Hydrogen from Natural Gas
Hydrogen barely exists in the atmosphere, often found as a part of other compounds - most notably in water, combined with oxygen atoms. Additionally, it has found various applications in energy, industry, and even in purely scientific fields. Hydrogen is also commonly present in a class of compounds known as hydrocarbon - composed primarily of carbon and hydrogen in materials like methane, known as a primary component of natural gas.
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"The production of hydrogen is important for many aspects of our life, such as fuel cells for cars and the manufacture of many useful chemicals such as ammonia," explains Zhenxing Feng, lead author of the study and a chemical engineering professor at Oregon State, in a statement. He adds that hydrogen is used in metal refinement and production of synthetic materials such as plastic, which is used in various applications.
According to the US Department of Energy, the United States produces most of its hydrogen from methane sources in a method known as steam-methane reforming. In this method, methane is introduced to pressurized steam. A catalytic agent is added, encouraging a chemical reaction that results in carbon monoxide and hydrogen, with a small amount of carbon dioxide as a byproduct.
It is followed by a water-gas shift reaction where carbon monoxide and steam are again subjected to a chemical reaction, this time using a different catalyst, drawing additional carbon dioxide and hydrogen in the process. Finally, in a method known as pressure-swing adsorption, carbon dioxide, and other remaining impurities are removed, leaving a product of pure hydrogen.
A Greener Alternative to Steam-Methane Reforming
"Compared to natural gas reforming, the use of electricity from renewable sources to split water for hydrogen is cleaner and more sustainable," Feng argues but noting that the efficiency of water-splitting is low. He explains that this is because of "high overpotential," or the difference between an electrochemical reaction's actual and theoretical potential, which constitutes an important reaction, the oxygen evolution reaction (OER).
He explains that electrocatalysts are important in promoting water-splitting reactions by reducing overpotential but acknowledges that the development of high-performance electrocatalysts is "far from straightforward." Among the existing constraints is the lack of details regarding the structure of electrocatalysts in the middle of operations.
"Understanding the structural and chemical evolution of the electrocatalyst during the OER is essential to developing high-quality electrocatalyst materials and, in turn, energy sustainability," Feng said.
Researchers then turned to study the structural evolution of strontium iridate (SrIrO3), an OER electrocatalyst, while in an acid electrolyte. They used synchrotron-based X-ray from Argonne and the X-ray photoelectron spectroscopy at Oregon State, allowing them to observe the transformation of the electrocatalyst during the OER process.
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