Synergistic Effect of Hydrogenation and Thiocyanate Treatments on Ag-Loaded TiO 2 Nanoparticles for Solar-to-Hydrogen Conversion

T. T. Wang, P. Raghunath, Y. G. Lin, Ming-Chang Lin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

H 2 evolution rate enhanced by Ag-loading on 25 nm TiO 2 anatase nanoparticles (denoted as Ag/TiO 2 ), Ag-loaded on hydrogenated TiO 2 NPs (Ag/H:TiO 2 ), as well as by the treatment of both NPs with potassium thiocyanate (KSCN) solution have been systematically investigated in conjunction with quantum-chemical calculations and XANES and EXAFS analyses with synchrotron radiation. We have observed a cumulative enhancement effect of these fabrication processes on solar to hydrogen (STH) conversion using a simulating light source. Ag/TiO 2 shows an enhanced visible absorption with 4-5 time increase in H 2 evolution over that of TiO 2 or H:TiO 2 prepared under mild hydrogenation conditions, while Ag/H:TiO 2 exhibits an even greater UV-visible absorption, similar to that of AgSCN/H:TiO 2 , with 3.1 times higher STH than that of Ag/TiO 2 . The treatment of Ag/TiO 2 and Ag/H:TiO 2 NPs with 0.1 mM KSCN solution further increases their STHs by 3.6 and 2.8 times, respectively. Optimization of KSCN concentration up to 0.2 mM gave [H 2 ] production rate rise to 2.75 mmol h -1 g -1 under Xe lamp illumination for the AgSCN/H:TiO 2 system, which has also been tested for its durability, showing a notable robustness. The observed synergistic effect of TiO 2 hydrogenation and SCN treatment of the Ag/H:TiO 2 NPs has been corroborated by the results of quantum chemical elucidation of H 2 production mechanism and the photocatalytic effects of Ag/H:TiO 2 and AgSCN/H:TiO 2 NPs revealed by appearances of new sub-band states within the TiO 2 bandgap, as well as by the result of XANES and EXAFS analyses which support the electron-pulling effect of the SCN group attached to Ag. Finally, we have also compared the efficacies of H 2 , HCOOH, and CH 3 OH as hydrogenation sources at 300 °C and the efficacies of CH 3 OH, C 2 H 5 OH, and sucrose as sacrificial agent to facilitate the separation of the electron from the hole.

Original languageEnglish
Pages (from-to)9681-9690
Number of pages10
JournalJournal of Physical Chemistry C
Volume121
Issue number18
DOIs
StatePublished - 11 May 2017

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