Electron dynamics of solvated titanium hydroxide

Abstract

Increasing interest in the photocatalytic activity of TiO₂ has led to the consideration of using TiO₂ nanoparticles in renewable energy generation. In order to better understand the electronic properties of nanoscale TiO₂ structures, it is important to understand fundamental components that serve as synthesis precursors of TiO₂ nanomaterials. Knowing the properties of basic building blocks of TiO₂ materials, such as titanium hydroxide, Ti(OH)₄, helps in a better understanding of the properties of larger scale structures. Titanium hydroxide is simulated in an explicit aqueous environment by density functional theory with hybrid functionals to model realistic conditions and to gain insight on mechanisms of how the charge carriers relax and recombine. Computed on-the-fly non-adiabatic couplings are determined from the first principles molecular dynamics calculations and allow the application of reduced density matrix formalism to calculate electron dynamics and dissipation times. An ultrafast charge transfer between ligand and metal is facilitated by energy dissipation via non-radiative relaxation occurring within a stepwise cascade thermalisation mechanism. The results show the possibility for design of promising and efficient materials for solar driven water splitting reactions.

Keywords:

• electronic transitions
• non-adiabatic dynamics
• reduced density matrix
• water splitting
• first principles modelling of water
• non-radiative transitions

Acknowledgements

Authors thank S. Huang, Q. Meng, H. Yao, S. Jensen, and Yulun Han for editing and thorough discussion. Authors acknowledge inspiring discussions on colloidal nanostructures synthesis with Professors Grigoriy Sereda, James Hoefelmeyer, and Ranjit Koodali. Gratitude is given to Doug Jennewein for maintaining the High Performance Computing facilities at the University of South Dakota.

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Additional information

Funding

This research was supported by NSF awards EPS-0903804, CHE-1413614 and by DOE, BES – Chemical Sciences, NERSC Contract No. DE-AC02-05CH11231, allocation Awards 85213, 86185, 86898, ‘Computational Modeling of Photo-catalysis and Photoinduced Charge Transfer Dynamics on Surfaces’.