Fast sampling in one step at room temperature delivers high efficiency at low cost.
Seawater makes up about 96% of all water on earth, making it an attractive resource to meet the world’s growing need for clean drinking water and carbon-free energy. And scientists already have the technical ability to desalinate seawater and split it to produce hydrogen, which is in demand as a source of clean energy.
But existing methods require several steps performed over a long period of time at high temperatures to produce a catalyst with the necessary efficiency. It requires significant amounts of energy and increases the cost.
Researchers from the University of Houston reported that an oxygen-producing catalyst only takes minutes to grow at room temperature on commercially available nickel foam. Combined with a previously reported hydrogen evolution reaction catalyst, it can achieve industrial required current density for the total splitting of seawater at low voltage. The work is described in a paper published in Energy and environmental science.
Zhifeng Ren, Director of the Texas Center for Superconductivity at UH (TcSUH) and corresponding author for the paper, says fast, cheap production is critical to commercialization.
“Any discovery, any technology development, no matter how good it is, the end cost is going to play the most important role,” he said. ‘If the cost is unpayable, it will not happen in the market. In this article, we have found a way to reduce costs so that commercialization will be easier and more acceptable for customers. ‘
A team of researchers led by Zhifeng Ren, director of the Texas Center for Superconductivity at the University of Houston, reported that a catalyst that develops oxygen only takes a few minutes to grow at room temperature and is able to clean drinking water and hydrogen to produce effectively from seawater. Credit: University of Houston
Ren’s research group and others previously reported a nickel-iron (oxy) hydroxide compound as a catalyst for the splitting of seawater, but the production of the material required a long process carried out at temperatures between 300 Celsius and 600 Celsius, or as high as 1100 degrees Fahrenheit. The high energy costs made it impractical for commercial use, and the high temperatures degraded the structural and mechanical integrity of the nickel foam, raising long-term stability concerns, Ren said. He 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 provide an effective catalyst at room temperature within five minutes. Working at room temperature has both reduced costs and improved mechanical stability, they said.
“To boost the hydrogen economy, it is essential to develop cost-effective and easy-to-use methodologies to synthesize NiFe-based (oxy) hydroxide catalysts for high-performance seawater electrolysis,” they wrote. “In this work, we have developed a one-step surface engineering approach to fabricate highly porous self-supporting S-doped Ni / Fe (oxy) hydroxide catalysts from commercial Ni foam within 1 to 5 minutes at room temperature.”
In addition to Ren, co-authors are the first writers 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 that the key to the researchers’ approach was the decision to use a chemical reaction to produce the desired material, rather than concentrating traditional energy consumption on physical transformation.
“This led us to the right structure, the right composition for the oxygen-evolving catalyst,” he said.
Reference: “Ultrasonic room temperature synthesis of porous S-doped Ni / Fe (oxy) hydroxide electrode 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 science.
DOI: 10.1039 / D0EE00921K