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Improving the photocatalytic reduction of CO2 to CO through immobilisation of a molecular Re catalyst on TiO2.

Windle CD, Pastor E, Reynal A, Whitwood AC, Vaynzof Y, Durrant JR, Perutz RN, Reisner E - Chemistry (2015)

Bottom Line: Photocatalytic CO2 reduction is even observed with ReP-TiO2 at wavelengths of λ>495 nm.Transient absorption spectroscopy suggests that the high activity upon heterogenisation is due to an increase in the lifetime of the immobilised anionic Re intermediate (t50% >1 s for ReP-TiO2 compared with t50% = 60 ms for ReP in solution) and immobilisation might also reduce the formation of inactive Re dimers.This study demonstrates that the activity of a homogeneous photocatalyst can be improved through immobilisation on a metal oxide surface by favourably modifying its photochemical kinetics.

View Article: PubMed Central - PubMed

Affiliation: Christian Doppler Laboratory for Sustainable SynGas Chemistry, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (U.K.); Department of Chemistry, University of York, Heslington, York YO10 5DD (U.K.).

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Transient absorption decays of the reduced intermediate ReP− probed at 500 nm after photoexcitation of the catalyst with 415 nm light (ca. 300 μJ cm−2, 0.5 Hz repetition rate) in the presence of a sacrificial electron donor TEOA (1 m). A) RePpic in solution and anchored onto TiO2 under N2; B) RePpic in solution and anchored to TiO2 under CO2 with an inset showing a second normalisation of the kinetics of the slow phase for both systems.
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fig04: Transient absorption decays of the reduced intermediate ReP− probed at 500 nm after photoexcitation of the catalyst with 415 nm light (ca. 300 μJ cm−2, 0.5 Hz repetition rate) in the presence of a sacrificial electron donor TEOA (1 m). A) RePpic in solution and anchored onto TiO2 under N2; B) RePpic in solution and anchored to TiO2 under CO2 with an inset showing a second normalisation of the kinetics of the slow phase for both systems.

Mentions: The kinetics of RePpic in solution and anchored on TiO2 were also monitored by transient absorption spectroscopy in the millisecond to second timescales (Figure 4). The measurements were performed under either an N2 or a CO2 atmosphere, using TEOA (1 m in DMF) as sacrificial electron donor. In all cases, the decays were probed at 500 nm, corresponding to λmax of the reduced catalytic intermediate ReP−. Under N2, the lifetime of ReP− is more than one order of magnitude longer-lived when the catalyst is anchored onto TiO2 than in solution (t50 %>1 s for RePpic–TiO2 and t50 %=60 ms for RePpic in homogeneous solution). The addition of CO2 in RePpic–TiO2 samples shortens the lifetime of the transient absorption decay assigned to ReP− to t50 %=400 ms. The decay of ReP− in solution, in the presence of CO2, has a strong biphasic behaviour, with a fast component in the 1–10 ms timescale and a slow phase in the 100 ms–1 s timescale, indicative of a multiple step process. The effect of the lifetime of the reaction intermediates on the CO2 reduction photocatalysis is further discussed below.


Improving the photocatalytic reduction of CO2 to CO through immobilisation of a molecular Re catalyst on TiO2.

Windle CD, Pastor E, Reynal A, Whitwood AC, Vaynzof Y, Durrant JR, Perutz RN, Reisner E - Chemistry (2015)

Transient absorption decays of the reduced intermediate ReP− probed at 500 nm after photoexcitation of the catalyst with 415 nm light (ca. 300 μJ cm−2, 0.5 Hz repetition rate) in the presence of a sacrificial electron donor TEOA (1 m). A) RePpic in solution and anchored onto TiO2 under N2; B) RePpic in solution and anchored to TiO2 under CO2 with an inset showing a second normalisation of the kinetics of the slow phase for both systems.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4471553&req=5

fig04: Transient absorption decays of the reduced intermediate ReP− probed at 500 nm after photoexcitation of the catalyst with 415 nm light (ca. 300 μJ cm−2, 0.5 Hz repetition rate) in the presence of a sacrificial electron donor TEOA (1 m). A) RePpic in solution and anchored onto TiO2 under N2; B) RePpic in solution and anchored to TiO2 under CO2 with an inset showing a second normalisation of the kinetics of the slow phase for both systems.
Mentions: The kinetics of RePpic in solution and anchored on TiO2 were also monitored by transient absorption spectroscopy in the millisecond to second timescales (Figure 4). The measurements were performed under either an N2 or a CO2 atmosphere, using TEOA (1 m in DMF) as sacrificial electron donor. In all cases, the decays were probed at 500 nm, corresponding to λmax of the reduced catalytic intermediate ReP−. Under N2, the lifetime of ReP− is more than one order of magnitude longer-lived when the catalyst is anchored onto TiO2 than in solution (t50 %>1 s for RePpic–TiO2 and t50 %=60 ms for RePpic in homogeneous solution). The addition of CO2 in RePpic–TiO2 samples shortens the lifetime of the transient absorption decay assigned to ReP− to t50 %=400 ms. The decay of ReP− in solution, in the presence of CO2, has a strong biphasic behaviour, with a fast component in the 1–10 ms timescale and a slow phase in the 100 ms–1 s timescale, indicative of a multiple step process. The effect of the lifetime of the reaction intermediates on the CO2 reduction photocatalysis is further discussed below.

Bottom Line: Photocatalytic CO2 reduction is even observed with ReP-TiO2 at wavelengths of λ>495 nm.Transient absorption spectroscopy suggests that the high activity upon heterogenisation is due to an increase in the lifetime of the immobilised anionic Re intermediate (t50% >1 s for ReP-TiO2 compared with t50% = 60 ms for ReP in solution) and immobilisation might also reduce the formation of inactive Re dimers.This study demonstrates that the activity of a homogeneous photocatalyst can be improved through immobilisation on a metal oxide surface by favourably modifying its photochemical kinetics.

View Article: PubMed Central - PubMed

Affiliation: Christian Doppler Laboratory for Sustainable SynGas Chemistry, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (U.K.); Department of Chemistry, University of York, Heslington, York YO10 5DD (U.K.).

No MeSH data available.


Related in: MedlinePlus