Scientists at the University of Kansas and the U.S. Department of Energy's Brookhaven National Laboratory have made significant progress in the division of hydrogen and oxygen molecules for the production of fossil fuel-free pure hydrogen.
Insights gained from pulse radiolysis experiments have revealed the comprehensive reaction mechanism of a crucial set of catalysts used in the process of "water-splitting." The collaborative efforts of researchers at KU and Brookhaven bring us closer to achieving the production of pure hydrogen from renewable energy sources. This breakthrough holds the potential to foster a more sustainable future for both our nation and the global community.
Co-author James Blakemore, an associate professor of chemistry, emphasized the immense difficulty in comprehending the intricate chemical reactions responsible for producing clean fuels such as hydrogen. He expressed that the publication signifies the culmination of a project he initiated during his inaugural year at KU. His groundbreaking research conducted in Lawrence serves as the foundation for this remarkable breakthrough.
"Our research paper unveils painstakingly acquired data obtained through specialized techniques, shedding light on the intricate workings of a specific catalyst employed in hydrogen generation," he explained. "The utilization of these specialized techniques, both at KU and Brookhaven, enabled us to comprehensively understand the process of producing hydrogen from its fundamental components-;protons and electrons. This in-depth understanding provides a complete picture of the hydrogen production mechanism."
Blakemore's research conducted at KU served as the fundamental basis for this significant breakthrough. To further investigate and advance his findings, he collaborated with Brookhaven's Accelerator Center for Energy Research, where he had access to a range of cutting-edge techniques, including pulse radiolysis. It is worth noting that Brookhaven is one of only two locations in the nation equipped with the necessary apparatus to conduct pulse radiolysis experiments. This collaboration allowed for a more comprehensive exploration of the research and facilitated the progression of knowledge in the field.
"Attaining a comprehensive understanding of an entire catalytic cycle is a rarity," remarked Dmitry Polyansky, a co-author of the paper and chemist at Brookhaven. "These reactions involve numerous intricate steps, some of which occur rapidly and are challenging to observe directly. Therefore, achieving a complete understanding of such complex processes is a significant accomplishment."
Blakemore and his team achieved this breakthrough by investigating a catalyst built upon a pentamethylcyclopentadienyl rhodium complex, commonly abbreviated as [CpRh]. Their primary focus was on the Cp (pronounced C-P-"star") ligand in conjunction with the rare metal rhodium. This selection was motivated by previous research suggesting that this particular combination would be well-suited for their intended investigation.
Blakemore expressed, "Our chosen rhodium system proved to be highly suitable for pulse radiolysis experiments. The widely recognized Cp* ligands, known to organometallic chemists and chemists from various backgrounds, are extensively employed to support numerous catalysts and can stabilize various species involved in catalytic cycles. A crucial discovery presented in our paper provides new perspectives on the vital role played by the Cp* ligand in the chemistry of hydrogen evolution. It sheds light on the intimate involvement of the Cp* ligand in this significant catalytic process."
But Blakemore stressed the findings could lead to other improved chemical processes besides producing clean hydrogen.
Blakemore emphasized the significance of their research, stating, "Through our study, we aim to demonstrate to chemists the remarkable reactivity that can be enabled by a commonly used ligand, Cp*. This unconventional reactivity is not only relevant to hydrogen-related applications but has broader implications. Cp* is widely present in various catalysts, and chemists typically attribute the crucial role in catalysis to the metal component. However, our findings challenge this conventional notion. We showcase that Cp* can play a pivotal role in assembling the molecular components and facilitating the formation of desired products. This highlights the broader potential and versatility of Cp* beyond traditional perceptions of catalysts solely relying on metals."
Blakemore expressed his aspiration for this paper to serve as a starting point for enhancing other catalysts and systems that utilize Cp* ligands. The breakthrough, backed by the National Science Foundation and the DOE Office of Science, holds the potential for broader applications in industrial chemistry. Blakemore's current endeavors involve leveraging similar techniques employed in this study to explore innovative methods for recycling nuclear fuels and managing actinide species. This demonstrates the expanding scope of their research and its implications for advancing various aspects of chemical science and technology.
KU students at the graduate and undergraduate levels also were involved in research that underpinned the breakthrough.
Blakemore highlighted the significance of this project as a valuable training platform for students. Wade Henke, the first author and a graduate student, has since advanced to a postdoctoral position at Argonne National Laboratory. Yun Peng, the second author and another graduate student, initiated the collaborative work with Brookhaven. Both have successfully completed their Ph.D. studies. Additionally, undergraduate students made valuable contributions to the project over the course of several years, providing new complexes and insights that played a crucial role in shaping the narrative presented in this paper. The involvement of students at various academic levels underscores the collaborative and educational nature of this research endeavor.
"All in all, I consider this a successful project and one that was a real team effort over the years."