Efficiently efficiently producing hydrogen from nearby water becomes a reality thanks to Oregon State University College of Engineering researchers and collaborators at Cornell University and the Argonne National Laboratory.
Scientists are using advanced experimental tools to gain a clearer understanding of cleaner and more sustainable electrochemical catalytic processes than the derivation of hydrogen from natural gas.
The findings were published on January 8, 2021, at Advances in Science.
Hydrogen is present in many compounds on Earth, most commonly combined with oxygen to make water, and has many scientific, industrial and energy roles. They also occur in the form of hydrocarbons, compounds made up of hydrogen and carbon such as methane, a major component of natural gas.
“Hydrogen production is important for many aspects of our lives, such as fuel cells for cars and the production of many useful chemicals such as ammonia,” said Oregon State’s Zhenxing Feng, a professor of chemical engineering. “It is also used in the refining of metals, to produce man-made materials such as plastic and for a number of other purposes.”
According to the Department of Energy, the United States produces most of its hydrogen from methane sources such as natural gas via a technique known as steam-methane reform. The process involves subjugation of methane to vaporized by the presence of a catalyst, creating a reaction that produces hydrogen and carbon monoxide, as well as a small amount of carbon dioxide.
The next step is called the gas-water shift reaction in which carbon monoxide and vapor are reacted through other catalysts, making carbon dioxide and hydrogen added. In the final step, adsorption of pressure oscillations, carbon dioxide, and other impurities is removed, leaving a pure hydrogen.
“Compared to the renewal of natural gas, the use of electricity from renewable sources becomes a water separator for cleaner and more sustainable hydrogen,” said Feng. “However, the efficiency of water separation is low, mainly because of the high potential – the difference between the actual potential and the theoretical potential of the electrochemical reaction – from one and a half key reactions in the process, the reaction of oxygen evolution or OER.”
A half-reaction is one of two parts of redox, or reduction-oxidation, a reaction in which electrons are transferred between two reactants; Reduction refers to the loss of electrons, oxidation means the loss of electrons.
The concept of half-reaction is often used to describe what is happening in electrochemical cells, and half-reaction is commonly used as a way to balance redox reactions. Excess potential is the margin between the theoretical voltage and the correct voltage required to cause electrolysis – a chemical reaction driven by the application of electric current.
“Electric electrodes are important to promote the reaction of water separation by lowering the potential, but developing high-performance electrocatalysts is far from straight,” said Feng. “One of the main obstacles is the lack of information about the evolutionary structure of electrocatalysts during electrochemical operations. Understanding the evolutionary structure and chemistry of electrocatalysts during OER is crucial for the development of high quality electrocatalyst materials and, in turn, energy sustainability.”
Feng and his collaborators use a sophisticated set of tools to study the atomic structural evolution of the state-of-the-art electrocatalyst OER, strontium iridate (SrIrO3), di sour electrolyte
“We want to know the origins of good activity for OER records – 1,000 times higher than commercial catalysts, iridium oxide,” said Feng. “Using a synchrotron-based X-ray facility in Argonne and laboratory photographic X-ray spectroscopy at the Northern Nanotechnology Infrastructure site at OSU, we observed surface chemistry and crystalline-to-amorphic transformation from SrIrO3 salami OER. “
The observation led to an in-depth understanding of what happens behind strontium iridate for its ability to work as well as being a catalyst.
“Our detailed findings of atomic scale explain how the active stridium iridate layer forms on strontium iridate and point to the critical role of lattice oxygen activation and ionic coupling in the formation of active OER units,” he said.
Feng adds that the work provides how the applied potential facilitates the formation of amorphous layers that function in the electrochemical interface and lead to the possibility of a better catalyst design.
References: “Amorphization mechanism of SrIrO3 electrocatalysts: How redox oxygen initiates ionic diffusion and structural reorganization “by Gang Wan, John W. Freeland, Jan Kloppenburg, Guido Petretto, Jocienne N. Nelson, Ding-Yuan Kuo, Cheng-Jun Sun, Jianguo Wen, J. Trey Diulus, Gregory S. Herman, Yongqi Dong, Ronghui Kou, Jingying Sun, Shuo Chen, Kyle M. Shen, Darrell G. Schlom, Gian-Marco Rignanese, Geoffroy Hautier, Dillon D. Fong, Zhenxing Feng, Hua Zhou and Jin Suntivich, 8 January 2021, Advances in Science.
DOI: 10.1126 / sciadv.abc7323
Collaborating with Feng is chemical engineering professor Gregory Herman, who heads the Northwest Nanotechnology Infrastructure Infrastructure site funded by the National Science Foundation in Oregon State, and Trey Diulus, a former Ph.D. student at OSU and currently a postdoctoral researcher at the University of Zurich in Switzerland.
Also contributing to the research were researchers from the Université Catholique de Louvain in Belgium, the University of Science and Technology of China and the University of Houston.