Light-induced Enhancement of Energetic Charge Carrier Extraction and Modulation of Local Charge Density to Impact Selectivity in Plasmonic Nanometals.

Localized surface plasmon resonance (LSPR) metals exhibit remarkable light-absorbing property and unique catalytic activity, attracting significant attention in photocatalysts recently. However, the practical application of plasmonic nanometal is hindered by challenge of energetic electrons extraction and low selectivity. The energetic carriers generated in nanometal under illumination have extremely short lifetimes, leading to rapid energy loss. In this work, silver nanometals modified with five distinct sulfhydryl ligands (re-Ag-S-R) were synthesized via photoreduction of superlattice precursors. Modified surface efficiently extracts and preserves excited state electrons of plasmonic nanometals. By modulation the local charge density at catalytic active sites through substituents with varying electron-donating and electron-withdrawing properties, the selectivity of the photocatalytic carbon dioxide reduction reaction and hydrogen evolution reaction was influenced. The results demonstrated opposite selectivity between methoxy-modified re-Ag-S-OCH3 (CO selectivity of 96.73 %) and amino-modified re-Ag-S-NH2 (H2 selectivity of 96.66 %) despite their similar structures. The changes in excited states and surface contact potentials induced by LSPR were monitored using femtosecond transient absorption (fs-TA) spectroscopy and Kelvin probe force microscopy (KPFM). Meanwhile, the detailed discussion of the LSPR mechanism in plasmonic nanometals will serve as valuable references and foundational elements for future research in this area.