Suffolk Reporter

Chemists at the U.S. Department of Energy’s Brookhaven National Laboratory have developed a theoretical framework to predict catalyst behavior more accurately. The study, published in Chem Catalysis, examines how temperature and pressure affect catalysts' structure, efficiency, and product formation.

Ping Liu, a theorist in Brookhaven Lab’s Chemistry Division and adjunct professor at Stony Brook University, led the research. "Our results highlight the significant impact the reaction environment can have on catalytic performance," Liu stated. The research shows that catalyst-environment interactions can be used to enhance catalysts' efficiency and selectivity.

The scientists modeled catalysts that convert carbon dioxide into various products like methanol using palladium combined with zinc or silver. Previous experiments showed metallic palladium produced formic acid while theoretical calculations suggested methanol should be favored. This discrepancy prompted further investigation.

Hong Zhang, Liu's graduate student at SBU and first author of the paper, designed a model using density function theory and kinetic modeling to understand these reactions better. "We developed a framework based on density function theory and kinetic modeling to capture the dynamic behavior and structure of the catalyst under operational reaction conditions," Zhang explained.

Liu noted that capturing reaction-driven dynamics experimentally is challenging. "The reality is that a catalyst often undergoes significant structural changes or phase transitions in the reaction environment," she said.

The new modeling framework aims to bridge studies of catalysts before and after reactions. It involves mapping out phase changes under different pressures and temperatures to determine which conditions favor certain products.

At room temperature, hydrogen blocked reactions from starting by covering catalytic surfaces. Increasing temperatures created hydrogen vacancies allowing carbon dioxide access to active sites for conversion into formic acid. Further temperature increases changed selectivity towards producing carbon monoxide and methanol.

"We found that changing the temperature actually changes the active sites of the catalyst," Liu said, explaining how larger hydrogen vacancies favored methanol production.

The framework was validated for other catalysts including pure palladium and alloys with zinc or silver. "In all three cases, the framework we developed can accurately describe the experimentally observed selectivity with significantly reduced computing cost," Liu added.

This work enhances understanding of catalyst structures and mechanisms while demonstrating how reaction conditions influence catalytic activity. Funded by DOE Office of Science, calculations utilized resources at Brookhaven Lab's Center for Functional Nanomaterials and Stony Brook University's SeaWulf computing system supported by NSF grants.