Fast installation in one step at room temperature ensures high efficiency at low cost.
Seawater makes up about 96% of all water on Earth, making it an enticing source to meet the world’s growing need for clean drinking water and carbon-free energy. And scientists have all the technical ability to both desalinate and split seawater to produce hydrogen, which is in high demand as a clean energy source.
However, existing methods require multiple steps performed at high temperatures over a long period of time to produce a catalyst with the required efficiency. This requires considerable amounts of energy and drives up costs.
Researchers at the University of Houston have reported an oxygen-evolving catalyst that takes just minutes to grow on commercially available nickel foam at room temperature. In combination with a previously reported hydrogen evolution reaction catalyst, it can achieve the industrially required current density for the overall low voltage cleavage of seawater. The work is described in a paper published in Energy and Environmental Sciences.
Zhifeng Ren, director of the Texas Center for Superconductivity at UH (TcSUH) and the paper’s corresponding author, said fast, low-cost production is critical to commercialization.
“Every discovery, every technological development, no matter how good it is, the ultimate cost will play the most important role,” he said. “If the costs are prohibitive, it will not make it to the market. In this document we have found a way to reduce costs so that commercialization becomes easier and more acceptable to customers. “
A team of researchers led by Zhifeng Ren, director of the Texas Center for Superconductivity at the University of Houston, has reported an oxygen-evolving catalyst that takes only minutes to grow at room temperature and is capable of efficiently producing both clean drinking water and produce hydrogen from seawater. Credit: University of Houston
The research group of Ren and others have previously reported a nickel-iron (oxy) hydroxide compound as a catalyst to split seawater, but producing the material required a lengthy process performed at temperatures between 300 Celsius and 600 degrees Celsius, or as high as 1,100 degrees Fahrenheit. The high energy costs made it impractical for commercial use, and the high temperatures impaired the nickel foam’s structural and mechanical integrity, making long-term stability a concern, said Ren, who is also MD Anderson professor of physics at UH.
To address both cost and stability, the researchers discovered a process to use nickel iron (oxy) hydroxide on nickel foam doped with a small amount of sulfur to produce an effective catalyst at room temperature within five minutes. Operating at room temperature reduced costs as well as improved mechanical stability, they said.
“To boost the hydrogen economy, it is necessary to develop cost-effective and convenient methodologies to synthesize NiFe-based (oxy) hydroxide catalysts for high-performance seawater electrolysis,” they wrote. “In this work, we developed a one-step surface engineering approach to fabricate highly porous self-supporting S-doped Ni / Fe (oxy) hydroxide catalysts from commercial Ni foam in 1 to 5 minutes at room temperature.”
In addition to Ren, co-authors include first author Luo Yu and Libo Wu, Brian McElhenny, Shaowei Song, Dan Luo, Fanghao Zhang and Shuo Chen, all with the UH Department of Physics and TcSUH; and Ying Yu from the College of Physical Science and Technology at Central China Normal University.
Ren said a key to the researchers’ approach was the decision to use a chemical reaction to produce the desired material, rather than the energy-consuming traditional focus on a physical transformation.
“That led us to the right structure, the right composition for the oxygen-evolving catalyst,” he said.
Reference: “Ultrafast Room Temperature Synthesis of Porous S-doped Ni / Fe (oxy) Hydroxide Electrodes for Oxygen Evolution Catalysis in Seawater Splitting” by Luo Yu, Libo Wu, Brian McElhenny, Shaowei Song, Dan Luo, Fanghao Zhang, Ying Yu , Shuo Chen and Zhifeng Ren, June 2, 2020, Energy and Environmental Sciences.
DOI: 10.1039 / D0EE00921K