Boosting up the Low Catalytic Activity of Silver for H2 Production on Ag/TiO2 Photocatalyst: Thiocyanate as a Selective Modifier

Yeoseon Choi, Hyoung Il Kim, Gun Hee Moon, Seongwon Jo, Wonyong Choi

Research output: Contribution to journalArticle

86 Citations (Scopus)

Abstract

Noble metal cocatalysts like Pt have been widely employed as an essential ingredient in many kinds of photocatalytic materials for solar hydrogen production. The high material cost of Pt is the biggest limitation. Silver is far less expensive but much less active than Pt and Au as a hydrogen evolving catalyst. Here we demonstrate a new strategy to boost up the activity of silver in Ag/TiO2 for photocatalytic H2 production via forming a simple surface complexation of thiocyanate (SCN-) on silver. The addition of thiocyanate in the suspension of Ag/TiO2 markedly enhanced the photocatalytic production of H2 by about 4 times. Thiocyanate was not consumed at all during the photoreaction, which ruled out the role of thiocyanate as an electron donor. Such a positive role of thiocyanate was not observed with bare TiO2, Pt/TiO2, and Au/TiO2. The selective chemisorption of thiocyanate on silver was confirmed by the analyses of Raman spectroscopy and spot-profile energy-dispersive spectroscopy. In the presence of thiocyanate, the overpotential for water reduction on Ag/TiO2 electrode was slightly reduced, and the interfacial charge transfer resistance on Ag/TiO2 (measured by electrochemical impedance spectroscopy) was significantly decreased, whereas other electrode systems (bare TiO2, Au/TiO2, and Pt/TiO2) showed the opposite effect of thiocyanate. These results indicate that the adsorption of thiocyanate on Ag facilitates the transfer of photogenerated electrons on the Ag/TiO2 electrode. It is proposed that the formation of Ag-SCN surface complex enhances the interfacial electron transfer rate and facilitates the reduction of protons on Ag/TiO2.

Original languageEnglish
Pages (from-to)821-828
Number of pages8
JournalACS Catalysis
Volume6
Issue number2
DOIs
Publication statusPublished - 2016 Feb 5

Fingerprint

Photocatalysts
Silver
Catalyst activity
Electrodes
Electrons
Chemisorption
Hydrogen production
Precious metals
Complexation
Electrochemical impedance spectroscopy
Raman spectroscopy
Charge transfer
Energy dispersive spectroscopy
Protons
Adsorption
Hydrogen
Catalysts
thiocyanate
Costs
Water

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)

Cite this

Choi, Yeoseon ; Kim, Hyoung Il ; Moon, Gun Hee ; Jo, Seongwon ; Choi, Wonyong. / Boosting up the Low Catalytic Activity of Silver for H2 Production on Ag/TiO2 Photocatalyst : Thiocyanate as a Selective Modifier. In: ACS Catalysis. 2016 ; Vol. 6, No. 2. pp. 821-828.
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Boosting up the Low Catalytic Activity of Silver for H2 Production on Ag/TiO2 Photocatalyst : Thiocyanate as a Selective Modifier. / Choi, Yeoseon; Kim, Hyoung Il; Moon, Gun Hee; Jo, Seongwon; Choi, Wonyong.

In: ACS Catalysis, Vol. 6, No. 2, 05.02.2016, p. 821-828.

Research output: Contribution to journalArticle

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T1 - Boosting up the Low Catalytic Activity of Silver for H2 Production on Ag/TiO2 Photocatalyst

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AU - Jo, Seongwon

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N2 - Noble metal cocatalysts like Pt have been widely employed as an essential ingredient in many kinds of photocatalytic materials for solar hydrogen production. The high material cost of Pt is the biggest limitation. Silver is far less expensive but much less active than Pt and Au as a hydrogen evolving catalyst. Here we demonstrate a new strategy to boost up the activity of silver in Ag/TiO2 for photocatalytic H2 production via forming a simple surface complexation of thiocyanate (SCN-) on silver. The addition of thiocyanate in the suspension of Ag/TiO2 markedly enhanced the photocatalytic production of H2 by about 4 times. Thiocyanate was not consumed at all during the photoreaction, which ruled out the role of thiocyanate as an electron donor. Such a positive role of thiocyanate was not observed with bare TiO2, Pt/TiO2, and Au/TiO2. The selective chemisorption of thiocyanate on silver was confirmed by the analyses of Raman spectroscopy and spot-profile energy-dispersive spectroscopy. In the presence of thiocyanate, the overpotential for water reduction on Ag/TiO2 electrode was slightly reduced, and the interfacial charge transfer resistance on Ag/TiO2 (measured by electrochemical impedance spectroscopy) was significantly decreased, whereas other electrode systems (bare TiO2, Au/TiO2, and Pt/TiO2) showed the opposite effect of thiocyanate. These results indicate that the adsorption of thiocyanate on Ag facilitates the transfer of photogenerated electrons on the Ag/TiO2 electrode. It is proposed that the formation of Ag-SCN surface complex enhances the interfacial electron transfer rate and facilitates the reduction of protons on Ag/TiO2.

AB - Noble metal cocatalysts like Pt have been widely employed as an essential ingredient in many kinds of photocatalytic materials for solar hydrogen production. The high material cost of Pt is the biggest limitation. Silver is far less expensive but much less active than Pt and Au as a hydrogen evolving catalyst. Here we demonstrate a new strategy to boost up the activity of silver in Ag/TiO2 for photocatalytic H2 production via forming a simple surface complexation of thiocyanate (SCN-) on silver. The addition of thiocyanate in the suspension of Ag/TiO2 markedly enhanced the photocatalytic production of H2 by about 4 times. Thiocyanate was not consumed at all during the photoreaction, which ruled out the role of thiocyanate as an electron donor. Such a positive role of thiocyanate was not observed with bare TiO2, Pt/TiO2, and Au/TiO2. The selective chemisorption of thiocyanate on silver was confirmed by the analyses of Raman spectroscopy and spot-profile energy-dispersive spectroscopy. In the presence of thiocyanate, the overpotential for water reduction on Ag/TiO2 electrode was slightly reduced, and the interfacial charge transfer resistance on Ag/TiO2 (measured by electrochemical impedance spectroscopy) was significantly decreased, whereas other electrode systems (bare TiO2, Au/TiO2, and Pt/TiO2) showed the opposite effect of thiocyanate. These results indicate that the adsorption of thiocyanate on Ag facilitates the transfer of photogenerated electrons on the Ag/TiO2 electrode. It is proposed that the formation of Ag-SCN surface complex enhances the interfacial electron transfer rate and facilitates the reduction of protons on Ag/TiO2.

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