Engineers developed a breakthrough method to generate hydrogen gas in one-step process

Hydrogen sulfide, infamous for its aroma of rotten eggs, is known to be highly poisonous and corrosive - especially in wastewater applications. Petrochemical plants and other industries make thousands of tons of this gas every year as a byproduct of various processes that separate sulfur from petroleum, natural gas, coal, and other products.

Now, Rice University engineers and scientists have devised a new way for such petrochemical industries to turn the noxious gas into "high-demand" hydrogen gas.

Rice engineer, physicist, and chemist Naomi Halas and the team have created a method that derives energy from light and employs gold nanoparticles to convert hydrogen sulfide and sulfur in one step.

In comparison, current catalytic technology refineries work through a method known as the Claus process, which requires multiple steps. Also, it produces sulfur but no hydrogen, which is converted into water.

"Hydrogen sulfide emissions can result in hefty fines for industry, but remediation is also very expensive," Halas, a nanophotonics pioneer whose lab has spent years developing commercially viable light-activated nanocatalysts, said in a statement. "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."

According to Halas, the process is economical; it could have low implementation costs and high efficiency to clean up nonindustrial hydrogen sulfide from sources like sewer gas and animal wastes.

The remediation process is economical and efficient

The team dotted the surface of grains of silicon dioxide powder with tiny "islands" of gold, according to the release. Each island was a gold nanoparticle that would interact with a wavelength of visible light. The reactions created "hot carriers," short-lived, high-energy electrons that can drive catalysis.

In a laboratory setup, the team demonstrated that a bank of LED lights could produce "hot carrier photocatalysis" and convert H2S directly into H2 gas and sulfur.

"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," added Halas.

Their findings are published in the American Chemical Society's journal ACS Energy Letters.

Abstract:

Plasmonic metal nanostructures have garnered rapidly increasing interest as heterogeneous photocatalysts, facilitating chemical bond activation and overcoming the high energy demands of conventional thermal catalysis. Here we report the highly efficient plasmonic photocatalysis of the direct decomposition of hydrogen sulfide into hydrogen and sulfur, an alternative to the industrial Claus process. Under visible light illumination and with no external heat source, up to a 20-fold reactivity enhancement compared to thermocatalysis can be observed. The substantially enhanced reactivity can be attributed to plasmon-mediated hot carriers (HCs) that modify the reaction energetics. With a shift in the rate-determining step of the reaction, a new reaction pathway is made possible with a lower apparent reaction barrier. Light-driven one-step decomposition of hydrogen sulfide represents an exciting opportunity for simultaneous high-efficiency hydrogen production and low-temperature sulfur recovery, important in many industrial processes.