Engineers and scientists at Rice University have developed a tasty method for petrochemical refineries to turn an unpleasant byproduct into money. The smell of rotten eggs is unmistakably present in hydrogen sulfide gas. Thousands of tons of the toxic gas are produced annually as a byproduct of processes that remove sulfur from petroleum, natural gas, coal, and other products. It frequently comes from sewers, stockyards, and landfills, but it is especially problematic for refineries, petrochemical plants, and other industries.
Naomi Halas, a Rice engineer, physicist, and chemist, and colleagues describe a process that uses gold nanoparticles to convert hydrogen sulfide into sulfur and high-demand hydrogen gas in a single step in a study that was published in the American Chemical Society’s high-impact journal ACS Energy Letters. Even better, the one-step process only needs light as its source of energy. Peter Nordlander of Rice University, Emily Carter of Princeton University, and Hossein Robatjazi of Syzygy Plasmonics are co-authors of the study.
“Hydrogen sulfide emissions can result in heavy fines for industry, but cleanup is also highly expensive,” said Halas, a pioneer in nanophotonics whose group has spent years creating light-activated nanocatalysts that are economically practical. “Although the term “game-changer” is overused, it is appropriate here. Plasmonic photocatalysis should be far less expensive to implement than conventional remediation, and it also has the potential to turn a costly burden into a commodity that is worth more and more money.
Each hydrogen sulfide gas molecule (H2S) consists of two hydrogen atoms and one sulfur atom. The main component of the hydrogen economy, clean-burning hydrogen gas (H2), has two hydrogen atoms in each of its molecules. In the latest research, Halas’ team placed tiny islands of gold on the surface of silicon dioxide powder grains. Each island was a gold nanoparticle that was 10 billionths of a meter across and had a strong interaction with a particular visible light wavelength. “Hot carriers,” or brief, high-energy electrons, are produced by these plasmonic processes and can power catalysis.
In the work, Halas and co-authors demonstrated how a bank of LED lights could effectively induce hot carrier photocatalysis and convert H2S straight into H2 gas and sulfur in a laboratory setting. Comparing it to the well-established catalytic process refineries employ to break down hydrogen sulfide is striking. It is referred to as the Claus process, and instead of producing hydrogen energy, it transforms sulfur into water. There are several steps in the Claus procedure as well, some of which call for combustion chambers to be heated to a temperature of roughly 1,500 degrees Fahrenheit.
Syzygy Plasmonics, a startup with more than 60 employees, including co-founders Halas and Nordlander, has obtained a license for the plasmonic hydrogen sulfide remediation technique.
According to Halas, the remediation procedure may end up being inexpensive for cleaning up non-industrial hydrogen sulfide from sources including sewer gas and animal wastes because of its low implementation costs and high efficiency.
The technique should be reasonably simple to scale up using renewable solar energy or extremely effective solid-state LED lighting, she added, as it just needs visible light and no external heating.
Halas and Nordlander received the esteemed 2022 Eni Energy Transition Award on October 3 in appreciation of their work creating effective light-powered catalysts for large-scale hydrogen production.
Halas is a professor of chemistry, bioengineering, physics, astronomy, materials science, and nanoengineering at Rice University. He also holds the Stanley C. Moore Chair in Electrical and Computer Engineering. Nordlander holds the Wiess Chair and is a professor of electrical and computer engineering, physics, astronomy, materials science, and nanoengineering at Rice. Carter is a professor emeritus of mechanical and aerospace engineering, applied and computational mathematics, and the Gerhard R. Andlinger Professor Emeritus in Energy and Environment at Princeton University. Robatjazi is the director of science at Syzygy Plasmonics and a chemistry adjunct professor at Rice.
The Welch Foundation (C-1220, C-1222), the Air Force Office of Scientific Research (FA9550-15-1-0022), and the Defense Threat Reduction Agency all provided funding for this study (HDTRA 1-16-1-0042).
