TY - JOUR
T1 - Synergistic Effect of Hydrogenation and Thiocyanate Treatments on Ag-Loaded TiO 2 Nanoparticles for Solar-to-Hydrogen Conversion
AU - Wang, T. T.
AU - Raghunath, P.
AU - Lin, Y. G.
AU - Lin, Ming-Chang
PY - 2017/5/11
Y1 - 2017/5/11
N2 -
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.
AB -
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.
UR - http://www.scopus.com/inward/record.url?scp=85020930325&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcc.7b00304
DO - 10.1021/acs.jpcc.7b00304
M3 - Article
AN - SCOPUS:85020930325
SN - 1932-7447
VL - 121
SP - 9681
EP - 9690
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 18
ER -