Understanding Competitive Photo-Induced Molecular Oxygen Dissociation and Desorption Dynamics atop a Reduced Rutile TiO₂(110) Surface: A Time-Domain Ab Initio Study

Abstract

Photochemical O 2 activation is the key to many photo-oxidation chemical reactions where the efficiency and chemical processes are significantly affected by the substrate−adsorbate interactions. However, the underlying mechanisms of the reactions are still unclear. Focusing on the reduced rutile TiO 2 (110) surface with an adsorbed O 2 , we perform time-domain density functional theory and nonadiabatic molecular dynamics simulations to investigate photo-induced O 2 dissociation and desorption processes. The simulations demonstrate that O 2 exhibits three distinct adsorption positions atop a reduced TiO 2 (110) surface where it prefers to adsorb at a bridge oxygen vacancy (O V ) site, followed by two metastable fivefold-coordinated Ti (Ti 5c ) sites, leading to the formation of peroxide O 2 2− by accepting two excess electrons of Ti 3+ ions induced by the O V . The adsorbed O 2 at an O V site creates no midgap states for capturing photo-excited holes and favors facile O 2 dissociation instead of desorption due to a small dissociation energy barrier, leaving the charge carrier lifetime up to over half a nanosecond. In contrast, midgap states composed of O 2 π* antibonding orbitals present in the two Ti 5c adsorption configurations are able to rapidly trap photoexcitation holes in the range of several to tens of picoseconds, which cause the elongation of the interfacial O−Ti bond length and drive O 2 desorption. The two Ti 5c adsorption configurations are switchable between each other and occur at Ti 5c sites due to the minute energy barriers, consolidating the experimental results. A good choice of a transition metal can enhance p−d polarization to manipulate the positions of O 2 antibonding orbitals and control O 2 chemical reactions. The reported results provide a fundamental understanding of the influence of the interplay between photoexcitation holes and the adsorbate−substrate interaction on O 2 dissociation and desorption. The study shows how electronic and charge properties can be controlled by dopants, allowing one to design high-performance transition metal oxide catalysts.

Recent Progress in Computational Design of Single-Atom/Cluster Catalysts for Electrochemical and Solar-Driven N2 Fixation

“…In the recent years, the decoherence-induced surface hopping (DISH) algorithm , has been employed in the framework of NAMD simulations to understand the just-mentioned phenomenon. Various inorganic monolayers (MoS 2 , WS 2 , ReS 2 , MoTe 2 , BP, InSe, doped phosphorene, and so on); organic monolayers (g-CN, g-C 3 N 4 , C 2 N, C 3 N, and many more); and bilayer organic–organic, inorganic–inorganic, and organic–inorganic van der Waals heterostructures have been treated with this NAMD formalism for qualitative estimation of their photophysical behavior. − Using these levels of calculation, many of these monolayers have been found to offer excellent photocatalytic activity for total water splitting to generate H 2 and O 2 as cleaner alternative energy fuels. However, the calculation of NRR activities of different mono- and bilayers (reported to be active photocatalysts through static electronic structure calculations) through NAMD simulations is yet to be performed.…”

Photocatalytic H 2 O‐to‐H 2 O 2 and ‐H 2 affected by Pd‐TiO 2‐δ /TiO 2

“…The incident light energy must be equal to or greater than the bandgap energy (BE) of a photocatalyst for the photoexcited electron and hole pairs separately in conduction and valence bands, respectively. The holes can oxidize H 2 O (l) to O 2 (E [H 2 O/O 2 ] = +1.23 V vs NHE), which involves in two‐electron reduction reaction step to yield H 2 O 2(aq) (E [O 2 /H 2 O 2 ] = +0.69 V vs NHE) 9‐12 . Simultaneously, the electrons can reduce H + (from H 2 O (l) splitting) to H 2(g) (E [H + /H 2 ] = −0.41 V vs NHE) 13,14 .…”

“…The holes can oxidize H 2 O (l) to O 2 (E [H 2 O/O 2 ] = +1.23 V vs NHE), which involves in two-electron reduction reaction step to yield H 2 O 2(aq) (E [O 2 /H 2 O 2 ] = +0.69 V vs NHE). [9][10][11][12] Simultaneously, the electrons can reduce H + (from H 2 O (l) splitting) to H 2(g) (E [H + /H 2 ] = À0.41 V vs NHE). 13,14 [15][16][17] The photocatalytic H 2 O-to-H 2 O 2(aq) and -H 2(g) for green energy have been widely studied.…”

Ultrafast Charge Transfer and Delayed Recombination in Graphitic-CN/WTe2 van der Waals Heterostructure: A Time Domain Ab Initio Study

“…The carrier lifetime has been found to be very sensitive to the size and shape of the nanomaterials . Since the discovery of atomically thin 2D materials such as graphene, boron nitride, transition metal dichalcogenides (TMDs), and transition metal nitrides (TMNs), they have been extensively employed in the area of nanoelectronics, spintronics, , photovoltaics, − energy storage devices, catalysts, and so on. − Doping of external atoms, creating atom or group vacancy, stacking of monolayers, and implementation of strain have been found to be efficient tools to generate efficient 2D materials for photovoltaic application with improved charge carrier lifetime. − …”