Understanding reaction mechanisms in water oxidation and CO<sub>2</sub> reduction catalysis

Ruthenium complex figure.

One of the most promising avenues towards a sustainable energy economy is the conversion of CO2 and water into chemical fuels using renewable energy sources. For this process to be economically viable, catalysts need to be developed for the various steps involved, but the molecular-level mechanisms in the catalytic generation of solar fuels are often poorly understood. At the current stage of research, it is important to investigate promising molecular catalysts and key intermediates in the proposed catalytic cycles in detail to connect molecular properties with catalyst performance, which can potentially guide catalyst design.
We use electrospray ionization to bring homogeneous (model) catalysts from solution into the gas phase, such as [Ru(II)(bpy)(tpy)]2+ for water oxidation, or a nickel polypyridine complex for CO2 reduction (see below). We then use cryogenic ion spectroscopy to obtain vibrational and electronic spectra for our target complexes. We interpret our spectra with the help of quantum chemistry calculations. You can click here for an example of our work on a water oxidation catalyst. We currently study homogeneous CO2 reduction catalysts based on transition metal complexes with polypyridine ligands and various macrocycles (e.g. porphines).

The nickel complex [Ni(II)(t-butyl-bpy)2(HCOO-)]+, representing the exit channel in the conversion of CO2 to formic acid.

This work is funded through an award from the NSF Division of Chemistry.