Rice University researchers and colleagues at Princeton and Syzygy Plasmonics have developed a plasmonic photocatalyst for the direct decomposition of hydrogen sulfide gas into hydrogen and sulfur, as an alternative to the industrial Claus process. A paper on the work appears in ACS Energy Letters.

An illustration of the light-powered, one-step remediation process for hydrogen sulfide gas made possible by a gold photocatalyst created at Rice University. (Image courtesy of Halas Group/Rice University)

Thousands of tons of the gas are made each year by refineries, petrochemical plants and other industries as a byproduct of processes that remove sulfur from petroleum, natural gas, coal and other products.

Rice engineer, physicist and chemist Naomi Halas and collaborators describe a one-step, light-driven method that uses gold nanoparticles to convert hydrogen sulfide into high-demand hydrogen gas and sulfur in a single step. Study co-authors include Rice’s Peter Nordlander, Princeton University’s Emily Carter and Syzygy Plasmonics’ Hossein Robatjazi.

Hydrogen sulfide emissions can result in hefty fines for industry, but remediation is also very expensive. The phrase ‘game-changer’ is overused, but in this case, it applies. Implementing plasmonic photocatalysis should be far less expensive than traditional remediation, and it has the added potential of transforming a costly burden into an increasingly valuable commodity.

—Naomi Halas

In the new study, Halas’ team dotted the surface of grains of silicon dioxide powder with tiny islands of gold. Each island was a gold nanoparticle about 10 billionths of a meter across that would interact strongly with a specific wavelength of visible light. These plasmonic reactions create “hot carriers,” short-lived, high-energy electrons that can drive catalysis.

In the study, Halas and co-authors used a laboratory setup and showed a bank of LED lights could produce hot carrier photocatalysis and efficiently convert H₂S directly into H₂ gas and sulfur. That’s a stark contrast to the established catalytic technology refineries use to break down hydrogen sulfide. Known as the Claus process, it produces sulfur but no hydrogen, which it instead converts into water. The Claus process also requires multiple steps, including some that require combustion chambers heated to about 1,500 degrees Fahrenheit.

The plasmonic hydrogen sulfide remediation technology has been licensed by Syzygy Plasmonics, a Houston-based startup company with more than 60 employees, whose co-founders include Halas and Nordlander.

Halas said the remediation process could wind up having low enough implementation costs and high enough efficiency to become economical for cleaning up nonindustrial hydrogen sulfide from sources such as sewer gas and animal wastes.

Given that it requires only visible light and no external heating, the process should be relatively straightforward to scale up using renewable solar energy or highly efficient solid-state LED lighting.

—Naomi Halas

The research was supported by the Welch Foundation (C-1220, C-1222), the Air Force Office of Scientific Research (FA9550-15-1-0022) and the Defense Threat Reduction Agency (HDTRA 1-16-1-0042).

Resources

• Minghe Lou, Junwei Lucas Bao, Linan Zhou, Gopal Narmada Naidu, Hossein Robatjazi, Aaron I. Bayles, Henry O. Everitt, Peter Nordlander, Emily A. Carter and Naomi J. Halas (2022) “Direct H₂S decomposition by plasmonic photocatalysis: Efficient remediation plus sustainable hydrogen production” ACS Energy Letters doi: 10.1021/acsenergylett.2c01755