Monitoring photoinduced charge transfer dynamics in wet nanoplasmonic light-harvesting systems using time-resolved ambient pressure x-ray photoelectron spectroscopy

Improving the efficiency and economic viability of hydrogen production via photoelectrochemical (PEC) water splitting is a major hurdle for clean and renewable hydrogen production. One promising system utilizes plasmonic metal nanoparticles (NPs) to improve light harvesting and charge separation in wide-bandgap semiconductor systems, enhancing visible light absorption and photocatalytic performance. Here, a model system of 20 nm gold NPs atop a layer of TiO₂ is studied with picosecond time-resolved ambient pressure x-ray photoelectron spectroscopy (TRAPXPS) to observe charge carrier dynamics in real-time with electron donor and acceptor site specificity. Measurements both in vacuum (dry) and with a background pressure of ~9 Pa of water vapor (wet) are performed and compared with previous results.^1,2 Recombination dynamics under both dry and wet conditions were substantially faster in recent measurements; however, the timescale of the wet sample charge separation dynamics remained orders of magnitude faster. Differences and similarities between current and previous results will be discussed in the context of the different sample preparation conditions.

1 Borgwardt, M. et al. J. Phys. Chem. Lett. 11, 5476-5481 (2020)

2 Fraund, M. et al. OSA Technical Digest Tu4A.20 (2021)