Modification of Nanocrystalline WO₃ with a Dicationic Perylene Bisimide: Applications to Molecular Level Solar Water Splitting

Abstract

[(N,N'-Bis(2-(trimethylammonium)ethylene) perylene 3,4,9,10-tetracarboxylic acid bisimide)(PF6)2] (1) was observed to spontaneously adsorb on nanocrystalline WO3 surfaces via aggregation/hydrophobic forces. Under visible irradiation (λ > 435 nm), the excited state of 1 underwent oxidative quenching by electron injection (kinj > 10(8) s(-1)) to WO3, leaving a strongly positive hole (Eox ≈ 1.7 V vs SCE), which allows to drive demanding photo-oxidation reactions in photoelectrochemical cells (PECs). The casting of IrO2 nanoparticles (NPs), acting as water oxidation catalysts (WOCs) on the sensitized electrodes, led to a 4-fold enhancement in photoanodic current, consistent with hole transfer from oxidized dye to IrO2 occurring on the microsecond time scale. Once the interaction of the sensitizer with suitable WOCs is optimized, 1/WO3 photoanodes may hold potentialities for the straightforward building of molecular level devices for solar fuel production.

Perylene Diimide Aggregates on Sb-Doped SnO2: Charge Transfer Dynamics Relevant to Solar Fuel Generation

“…In this contribution we extend our previous work on the use of PDI-sensitized photoanodes for water oxidation, in which the redox properties of the PDI's ground and excited state were assessed in ACN solution. 15 Herein we report the electrochemical and spectroscopic characterization of PDI aggregates, formed upon deposition on different substrates, showing that these species still meet the thermodynamic requirements of photoanodic assemblies. Indeed, as evidenced in Figure S1A, the PDI aggregates…”

“…Colloidal IrO 2 nanoparticles (NPs) solution was prepared by following literature procedures 25 and deposited onto ATO-PDI photoelectrodes by means of spin coating. 15 …”

“…Recently, it has been shown that even sensitizers without any specific anchoring site can adsorb/aggregate in a very stable fashion onto the surfaces of these materials by hydrophobic/pi-stacking interactions. 15 Following this latter approach, we have investigated the charge separation dynamics in different wide band gap porous semiconductors sensitized with aggregates of perylene diimidebased dyes (namely [(N,N′-bis(2-(trimethylammonium)-ethylene)-perylene-3,4,9,10-tetracarboxylic acid bis-imide)]-(PF 6 ) 2 , PDI, and the hexacationic derivative PDI2, see Figure 1), with the aim of finding substrates with optimized photoinduced charge separation.…”

A Dynamic View of Proton-Coupled Electron Transfer in Photocatalytic Water Splitting

“…[6][7][8][9][10][11][12] A photoelectrochemical solar fuel cell device combines the functions of light harvesting, charge separation and catalysis. [13][14][15] In the last decade several systems have been proposed employing either metal oxide nanoparticles 8,[16][17][18][19][20][21][22][23][24] or molecular complexes 8,[25][26][27][28] as water oxidation catalyst (WOC). Furthermore, the coupling between the WOC, the chromophore and an electron accepting semiconductor into a photoanode has been achieved through co-absorption of both the catalyst and the chromophore 16,[29][30][31][32] or through dye-WOC supramolecular complexes.…”

Real roles of perylenetetracarboxylic diimide for enhancing photocatalytic H2-production

“…As the visible-light collector, perylene derivatives have been investigated in photoelectrochemical water-splitting systems [26][27][28]. Quite recently, Caramori and Bignozzi et al [29] used dicationic PDI as sensitizer to inject charges to WO 3 , which resulted in long-lived charge separated states in the heterogeneous phase and hole transfer to the sacrificial hole scavenger for photo-oxidation reactions.…”