TITLE: Capturing Catalysis in Motion: Picosecond X Ray Views of Hydrogen Evolving Molecular Complexes
AUTHOR: Dooshaye Moonshiram. Heterostructures for Optics and optoelectronics group (ICMM).
WHEN: February, 19th - 12PM
WHERE: Salón de Actos, ICMM-CSIC
ABSTRACT: Replacing fossil fuels with renewable energy sources represents one of the most promising approaches for addressing the global energy crisis. While substantial progress has been made in generating electricity from solar, wind, tidal, and hydroelectric power, these intermittent sources remain limited without reliable strategies for energy storage and transport. A compelling solution lies in converting solar energy into chemical energy through fuel‑forming reactions inspired by natural photosynthesis, for example, light-driven water splitting to generate hydrogen and oxygen. The potential of molecular hydrogen as a carbon‑free, high‑energy-density fuel has stimulated extensive efforts to design catalysts for photo‑induced water oxidation, proton reduction, and integrated photosensitizer–catalyst assemblies. Despite significant synthetic advances and the development of increasingly efficient water‑splitting complexes, a fundamental gap persists in understanding how catalyst structure, stability, and ligand geometry govern performance.
In this context, time‑resolved X‑ray absorption spectroscopy (XAS) combined with X‑ray emission spectroscopy (XES) provides a uniquely powerful platform for visualizing electronic and geometric changes in photocatalytic systems with picosecond‑to‑microsecond time resolution. This talk will explore the reaction pathways of cobalt‑, nickel‑, and copper‑based photosensitizers and hydrogen‑evolving complexes, characterized with unprecedented temporal precision using picosecond X‑ray probes. The mechanistic trajectories of these catalysts, including spectroscopic and kinetic identification of key intermediates involved in hydrogen evolution and H–H bond formation, will be presented. By integrating experimental measurements with advanced theoretical simulations, we uncover new insights into the structures, energetics, and time scales that define catalytic intermediates during hydrogen evolution under purely aqueous conditions. The findings open pathways for the rational design of next‑generation molecular photocatalysts capable of operating at faster time scales than the current microsecond limit, and highlight how tailored ligand environments can enhance protonation efficiency and overall catalytic performance.
