New catalyst brings seawater desalination and hydrogen production closer to commercialization

Rapid, one-step assembly at room temperature offers high efficiency at low cost.

Seawater makes up around 96% of all water on earth, making it a tempting resource to meet the world’s growing needs for clean drinking water and carbon-free energy. And scientists already have the technical ability to both desalinate seawater and divide it to produce hydrogen, which is in demand as a clean energy source.

But existing methods require multiple steps carried out at high temperatures over a long period of time in order to produce a catalyst with the necessary efficiency. This requires substantial amounts of energy and increases costs.

Researchers at the University of Houston have reported an oxygen-releasing catalyst that only takes a few minutes to develop at room temperature on commercially available nickel foam. Combined with a previously reported hydrogen evolution reaction catalyst, it can achieve the current density industrially required for the global division of seawater at low voltage. The work is described in an article published in Energy and environmental sciences.

Zhifeng Ren, director of the Texas Center for Superconductivity at UH (TcSUH) and corresponding author of the article, said rapid, low-cost production is essential for commercialization.

“Any discovery, any technological development, no matter how good, the final cost will play the most important role,” he said. “If the cost is prohibitive, it will not be marketed. In this article, we found a way to cut costs so that marketing is 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, reported an oxygen-releasing catalyst that only takes a few minutes to develop at room temperature and is able to produce efficiently at both clean drinking water and hydrogen from seawater. Credit: University of Houston

Ren’s research group and others have previously reported a compound of nickel-iron hydroxide (oxy) as a catalyst to split seawater, but the production of the material required a long process driven at temperatures between 300 Celsius and 600 Celsius, or as high as 1100 degrees Fahrenheit. The high energy cost made it impractical for commercial use, and the high temperatures degraded the structural and mechanical integrity of the nickel foam, making long-term stability an issue, said Ren, who is also MD Anderson physics professor at UH.

To address both cost and stability, researchers discovered a method of using nickel-iron hydroxide (oxy) on nickel foam, doped with a small amount of sulfur to produce a catalyst. effective at room temperature in five minutes. Working at room temperature reduced the cost and improved mechanical stability, they said.

“To stimulate the hydrogen economy, it is imperative to develop cost-effective and easy methodologies for synthesizing NiFe-based hydroxide (oxy) catalysts for high performance seawater electrolysis,” said they wrote. “In this work, we have developed a one-step surface engineering approach to fabricate highly porous self-supported S-doped Ni / Fe (oxy) hydroxide catalysts from commercial Ni foam in 1 to 5. minutes at room temperature. “

Besides 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 Sciences and Technology, Central China Normal University.

Ren said one of the keys to the researchers’ approach was the decision to use a chemical reaction to produce the desired material, rather than the traditional energy-consuming focus on physical transformation.

“This led us to the right structure, the right composition for the oxygen-releasing catalyst,” he said.

Reference: “Ultrafast synthesis at room temperature of porous S-doped Ni / Fe (oxy) hydroxide electrodes for the catalysis of the evolution of oxygen in the division of sea water” 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