A team of researchers from the National Energy Technology Laboratory (NETL) and the University of Pittsburgh has developed a new high-performance catalyst that electrochemically converts carbon dioxide and water into formic acid, which can be used as a hydrogen carrier. An open-access paper detailing the research appears in the journal Applied Catalysis B: Environmental.

Formic acid is also an important chemical product as well as a major player in synthetic chemistry as an acid, a reductant, and a carbon source. Research on the conversion of CO₂ to formic acid has been underway for years, e.g. earlier post.

We carefully optimized the catalyst formulation to maximize performance, and the demonstrated activity and product selectivity are among the highest reported in the literature.

—lead author Thuy Duong Nguyen Phan

Formic acid is a versatile liquid product that has potential uses in fuel cells, agricultural, chemical and pharmaceutical applications. Additionally, and more importantly for our nation’s decarbonization goals, formic acid produced via CO2R has been identified as an economically viable green hydrogen carrier, which means that the hydrogen is stored in another form and then separated out when needed. The liquid state of formic acid reduces the challenges associated with compressing, transporting and storing gaseous hydrogen.

—NETL co-authors James Ellis and Douglas Kauffman

Deliberately adding sulfur into tin-based catalysts (doping) has been shown to improve CO2R activity and selectivity; however, the precise relationship between sulfur-dopant levels and catalyst performance remains largely unexplored from an experimental standpoint.

In this work, the NETL-led team sought to close that knowledge gap and experimentally quantified the composition-dependent role of sulfur dopants, demonstrating that its beneficial influence on CO₂ conversion only occurs over a very narrow composition range.

We investigated various concentrations of sulfur dopants between approximately 1 and 11%. Surprisingly it was at the lower end, about 1.4% sulfur content, that we saw the most promising results—a five-fold improvement in conversion performance compared to an undoped catalyst. This shows that a little bit of sulfur dopant goes a long way to improving catalyst performance—something no one has shown before.

—Thuy Duong Nguyen Phan

The research will help provide further insight into the design of high-performance CO2R electrocatalysts.

Resources

• Thuy-Duong Nguyen-Phan, James E. Ellis, Anantha Venkataraman Nagarajan, Bret H. Howard, Giannis Mpourmpakis, Douglas R. Kauffman (2024) “Precisely doping the surface of tin-based electrocatalysts for improved CO2 conversion to liquid chemicals,” Applied Catalysis B: Environmental, Volume 340, doi: 10.1016/j.apcatb.2023.123250