Taking molecular snapshots in solar fuel generation processes with pulsed X-rays

Transient molecular structures along reaction coordinates, both electronic and nuclear configurations, in solar fuel generation and related processes have been obtained by pulsed x-rays using laser-initiated time-resolved x-ray absorption spectroscopy (LITR-XAS) which has been developed in our lab and elsewhere during last decade. Information of these transition molecular structures combined with molecular dynamics and energetics obtained from complementary ultrafast optical transient absorption/emission spectroscopy provides us insight into reaction mechanisms and the correlations of electron and nuclear movements during energy and electron transfer processes during solar fuel generation. A few examples will be presented on molecular structural dynamics studies of metalloporphyrins, excited state transition metal complexes, and metal nanoparticle or metal complex /titanium oxide nanoparticles interfacial systems whose transient structures are closely related to their functions in solar fuel generation.