TY - JOUR

T1 - Mechanistic Insights into Hydrogen Evolution by Photocatalytic Reforming of Naphthalene

AU - Al-Madanat, Osama

AU - Alsalka, Yamen

AU - Curti, Mariano

AU - Dillert, Ralf

AU - Bahnemann, Detlef W.

N1 - Funding information: Financial support from the Katholischer Akademischer Ausländer-Dienst (KAAD) is gratefully acknowledged for providing a scholarship for Osama Al-Madanat to perform his Ph.D. Y.A. gratefully acknowledges the financial support from the Deutscher Akademischer Austauschdienst (DAAD) and the Federal Foreign Office. M.C. is grateful to the DAAD together with the Ministerio de Educación, Cultura, Ciencia y Tecnología (Argentina), for his ALEARG scholarship. O.A.-M. wishes to thank Dr. Samia Ben Hammouda for the helpful discussion while preparing the manuscript. The authors thank Carsten Günnemann for helping with the transient absorption spectroscopy analysis. This work was supported by Saint-Petersburg State University via a research grant ID 32706707. Financial support from the Global Research Laboratory Program (2014 K1 A1 A2041044), Korea Government (MSIP), through NFR is gratefully acknowledged.

PY - 2020/7/2

Y1 - 2020/7/2

N2 - Heterogeneous photocatalysis has been widely considered, among other applications, for environmental remediation and hydrogen production. While these applications have been traditionally seen as well-separated areas, recent examples have highlighted the possibility of coupling them. Here, we demonstrate the simultaneous production of H2 and naphthalene removal from aqueous solutions with (unoptimized) photonic efficiencies of 0.97 and 0.33%, respectively, over Pt-TiO2 under simulated sunlight. Photocatalytic and spin-trapping experiments in the presence of a hydroxyl radical and hole scavengers evinced that only the photogenerated holes play a significant role in the oxidation of naphthalene. Isotopic labeling analyses showed that the evolved H2 isotopologues match those of the solvent and that deuterated water (but not deuterated naphthalene) decreases the reaction rate, suggesting its involvement in the rate-determining step. Moreover, the use of Ti18O2 does not lead to the significant formation of 18O-enriched CO2, suggesting that water is the source of the oxygen atoms. Ultimately, by considering the stable and transient reaction intermediates, we propose a plausible reaction pathway. Our work illustrates that environmental remediation can be effectively coupled to solar fuel production, providing a double purpose to photocatalytic reactions, while the mechanistic insights will be of use for the further development of this strategy.

AB - Heterogeneous photocatalysis has been widely considered, among other applications, for environmental remediation and hydrogen production. While these applications have been traditionally seen as well-separated areas, recent examples have highlighted the possibility of coupling them. Here, we demonstrate the simultaneous production of H2 and naphthalene removal from aqueous solutions with (unoptimized) photonic efficiencies of 0.97 and 0.33%, respectively, over Pt-TiO2 under simulated sunlight. Photocatalytic and spin-trapping experiments in the presence of a hydroxyl radical and hole scavengers evinced that only the photogenerated holes play a significant role in the oxidation of naphthalene. Isotopic labeling analyses showed that the evolved H2 isotopologues match those of the solvent and that deuterated water (but not deuterated naphthalene) decreases the reaction rate, suggesting its involvement in the rate-determining step. Moreover, the use of Ti18O2 does not lead to the significant formation of 18O-enriched CO2, suggesting that water is the source of the oxygen atoms. Ultimately, by considering the stable and transient reaction intermediates, we propose a plausible reaction pathway. Our work illustrates that environmental remediation can be effectively coupled to solar fuel production, providing a double purpose to photocatalytic reactions, while the mechanistic insights will be of use for the further development of this strategy.

KW - EPR

KW - Hproduction

KW - isotopic study

KW - persistent organic pollutants

KW - photoreforming

KW - polycyclic aromatic hydrocarbons

KW - reaction mechanism

KW - titania

KW - H production

UR - http://www.scopus.com/inward/record.url?scp=85088008686&partnerID=8YFLogxK

U2 - 10.1021/acscatal.0c01713

DO - 10.1021/acscatal.0c01713

M3 - Article

VL - 10

SP - 7398

EP - 7412

JO - ACS catalysis

JF - ACS catalysis

SN - 2155-5435

IS - 13

ER -