Effects of Surface Anchoring Groups (Carboxylate vs Phosphonate) in Ruthenium-Complex-Sensitized TiO<sub>2</sub> on Visible Light Reactivity in Aqueous Suspensions

Bae, Eunyoung; Choi, Wonyong; Park, Jaiwook; Shin, Hyeon Suk; Kim, Seung Bin; Lee, Jae Sung

doi:10.1021/jp047777p

Cited by 286 publications

(248 citation statements)

References 44 publications

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“…It should be noted that a large effect of anchor group on molecular conductance was pointed out in a previous theoretical study. 84 These anchoring groups differ in both the binding strength to surface 27,[48][49][50][51][52][53] and electronic structure. 52, 54 Stronger binding of phosphonate to TiO 2 than the carboxylate anchoring group has been observed in experiments 27,[48][49][50][51][52][53] and confirmed in computational modeling.…”

Section: Ph Dependence Of Photophysicsmentioning

confidence: 99%

“…84 These anchoring groups differ in both the binding strength to surface 27,[48][49][50][51][52][53] and electronic structure. 52, 54 Stronger binding of phosphonate to TiO 2 than the carboxylate anchoring group has been observed in experiments 27,[48][49][50][51][52][53] and confirmed in computational modeling. 54 A recent periodic hybrid HF-DFT study of HPO 3 H 2 and HCOOH on anatase TiO 2 (101) surface has found the binding energy in the former to be ∼20 kcal/mol larger.…”

Section: Ph Dependence Of Photophysicsmentioning

confidence: 99%

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pH-Dependent Electron Transfer from Re-bipyridyl Complexes to Metal Oxide Nanocrystalline Thin Films

et al. 2005

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Photoinduced interfacial electron transfer (ET) from molecular adsorbates to semiconductor nanoparticles has been a subject of intense recent interest. Unlike intramolecular ET, the existence of a quasicontinuum of electronic states in the solid leads to a dependence of ET rate on the density of accepting states in the semiconductor, which varies with the position of the adsorbate excited-state oxidation potential relative to the conduction band edge. For metal oxide semiconductors, their conduction band edge position varies with the pH of the solution, leading to pH-dependent interfacial ET rates in these materials. In this work we examine this dependence in Re(L P )(CO) 3 Cl (or ReC1P) [L P ) 2,2′-bipyridine-4,4′-bis-CH 2 PO(OH) 2 ] and Re-(L A )(CO) 3 Cl (or ReC1A) [L A ) 2,2′-bipyridine-4,4′-bis-CH 2 COOH] sensitized TiO 2 and ReC1P sensitized SnO 2 nanocrystalline thin films using femtosecond transient IR spectroscopy. ET rates are measured as a function of pH by monitoring the CO stretching modes of the adsorbates and mid-IR absorption of the injected electrons. The injection rate to TiO 2 was found to decrease by 1000-fold from pH 0-9, while it reduced by only a factor of a few to SnO 2 over a similar pH range. Comparison with the theoretical predictions based on Marcus' theory of nonadiabatic interfacial ET suggests that the observed pH-dependent ET rate can be qualitatively accounted for by considering the change of density of electron-accepting states caused by the pH-dependent conduction band edge position.

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Section: Ph Dependence Of Photophysicsmentioning

confidence: 99%

Section: Ph Dependence Of Photophysicsmentioning

confidence: 99%

pH-Dependent Electron Transfer from Re-bipyridyl Complexes to Metal Oxide Nanocrystalline Thin Films

et al. 2005

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“…As a mean to achieve this goal, semiconductor photocatalysts have been extensively studied. In particular, a variety of visible light-active photocatalyts [2][3][4][5][6] including CdS [7][8][9][10][11][12][13] have been studied. In terms of the band gap magnitude and the position of band edges, CdS is ideally suited for photocatalytic water splitting but it is not effective at all unless suitable electron donors (EDs) are present.…”

Section: Introductionmentioning

confidence: 99%

Effects of the preparation method of the ternary CdS/TiO2/Pt hybrid photocatalysts on visible light-induced hydrogen production

2008

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A variety of combinations of CdS, TiO 2 , and Pt in preparing the hybrid catalysts were studied for hydrogen production under visible light (l > 420 nm) irradiation. The preparation method sensitively influenced the activity of the ternary hybrid catalysts. The formation of the potential gradient at the interface between CdS and TiO 2 is necessary in achieving the efficient charge separation and transfer and how the platinum as a cocatalyst is loaded onto the CdS/TiO 2 hybrid catalysts determines the overall hydrogen production efficiency. The common method of photoplatinization of CdS/TiO 2 hybrid [Pt-(CdS/TiO 2 )] was much less efficient than the present method in which Pt was photodeposited on bare TiO 2 , which was followed by the deposition of CdS [CdS/(Pt-TiO 2 )]. The CdS/(Pt-TiO 2 ) has the hydrogen production rate ranging (6-9) Â 10, which is higher by a factor of 3-30 than that of Pt-(CdS/TiO 2 ). The photocatalytic activity of the ternary hybrid catalysts was extremely sensitive to where the platinum is loaded. The photoactivity of the hybrid catalyst was also assessed in terms of the photocurrent collected by the methyl viologen electron shuttle in the catalyst suspension. CdS/(Pt-TiO 2 ) generated higher photocurrents than Pt-(CdS/TiO 2 ) by a factor of 2-7. The extreme sensitivity of the preparation method to the hydrogen production activity should be taken into account when hybrid photocatalysts are designed and prepared.

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“…There remain significant interests in designing sensitizers with phosphonate anchoring groups because they have been shown to bind more strongly with metal oxide substrates than carboxylate and are expected to lead to better long-term cell stability. 8,[11][12][13][14][15][16] The incident photon-to-current conversion efficiency was found to be near unity in RuN3-sensitized TiO 2 solar cells, 2,10 and the high efficiency has been attributed to an ultrafast electron injection and a much slower charge recombination that happens on the microsecond to millisecond time scales. [17][18][19] The injection kinetics has been shown to be biphasic, consisting of a primary <100 fs component and slower components on a few to tens of picosecond time scales.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Interfacial Electron Transfer through Carboxylate and Phosphonate Anchoring Groups^†

et al. 2007

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The effects of anchoring groups on electron injection from adsorbate to nanocrystalline thin films were investigated by comparing injection kinetics through carboxylate versus phosphonate groups to TiO 2 and SnO 2 . In the first pair of molecules, Re(L A )(CO) 3 Cl (ReC1A) and Re(Lp)(CO)3Cl (ReC1P), [L A ) 2,2′-bipyridine-4,4′-bis-CH 2 -COOH, Lp) 2,2′-bipyridine-4,4′-bis-CH 2 -PO 3 H 2 ], the anchoring groups were insulated from the bipyridine ligand by a CH 2 group. In the second pair of molecules, Ru(dcbpyH 2 ) 2 (NCS) 2 (RuN3) and Ru(bpbpyH 2 ) 2 (NCS) 2 (RuN3P), [dcbpy ) 2,2′-bipyridine-4,4′-biscarboxylic acid, bpbpy ) 2,2′-bipyridine-4,4′-bisphosphonic acid], the anchoring groups were directly connected to the bipyridine ligands. The injection kinetics, as measured by subpicosecond IR absorption spectroscopy, showed that electron injection rates from ReC1P to both TiO 2 and SnO 2 were faster than those from ReC1A. The injection rates from RuN3 and RuN3P to SnO 2 films were similar. On TiO 2 , the injection kinetics from RuN3 and RuN3P were biphasic: carboxylate group enhances the rate of the <100 fs component, but reduces the rate of the slower components. To provide insight into the effect of the anchoring groups, the electronic structures of Re-bipyridyl-Ti model clusters containing carboxylate and phosphonate anchoring groups and with and without a CH 2 spacer were computed using density functional theory. With the CH 2 spacer, the phosphonate group led to a stronger electronic coupling between bpy and Ti center than the carboxylate group, which accounted for the faster injection from ReC1P than ReC1A. When the anchoring groups were directly connected to the bpy ligand without the CH 2 spacer, such as in RuN3 and RuN3P, their effects were 2-fold: the carboxylate group enhanced the electronic coupling of bpy π* with TiO 2 and lowered the energy of the bpy orbital. How these competing factors led to different effects on TiO 2 and SnO 2 and on different components of the biphasic injection kinetics were discussed.

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Effects of Surface Anchoring Groups (Carboxylate vs Phosphonate) in Ruthenium-Complex-Sensitized TiO₂ on Visible Light Reactivity in Aqueous Suspensions

Cited by 286 publications

References 44 publications

pH-Dependent Electron Transfer from Re-bipyridyl Complexes to Metal Oxide Nanocrystalline Thin Films

pH-Dependent Electron Transfer from Re-bipyridyl Complexes to Metal Oxide Nanocrystalline Thin Films

Effects of the preparation method of the ternary CdS/TiO2/Pt hybrid photocatalysts on visible light-induced hydrogen production

Comparison of Interfacial Electron Transfer through Carboxylate and Phosphonate Anchoring Groups^†

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Effects of Surface Anchoring Groups (Carboxylate vs Phosphonate) in Ruthenium-Complex-Sensitized TiO2 on Visible Light Reactivity in Aqueous Suspensions

Cited by 286 publications

References 44 publications

pH-Dependent Electron Transfer from Re-bipyridyl Complexes to Metal Oxide Nanocrystalline Thin Films

pH-Dependent Electron Transfer from Re-bipyridyl Complexes to Metal Oxide Nanocrystalline Thin Films

Effects of the preparation method of the ternary CdS/TiO2/Pt hybrid photocatalysts on visible light-induced hydrogen production

Comparison of Interfacial Electron Transfer through Carboxylate and Phosphonate Anchoring Groups†

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Effects of Surface Anchoring Groups (Carboxylate vs Phosphonate) in Ruthenium-Complex-Sensitized TiO₂ on Visible Light Reactivity in Aqueous Suspensions

Comparison of Interfacial Electron Transfer through Carboxylate and Phosphonate Anchoring Groups^†