Issue 37, 2016

Design of nitrogen-doped layered tantalates for non-sacrificial and selective hydrogen evolution from water under visible light

Abstract

Nitrogen doping into a series of layered tantalates (ALaTa2O7, where A = Li, Na, K, Rb, or Cs) was attempted in order to produce materials capable of catalyzing non-sacrificial and endergonic water reduction under visible light. Heating of KLaTa2O7 and RbLaTa2O7 in an NH3 stream at 1073 K led to successful nitrogen doping, accompanied by a significant shift in the absorption edge of the material toward the visible-light region, while similar treatment of the other tantalates resulted in the collapse of the layered structure or partial anion substitution at the surface. Although the NH3 heating of a conventional RbLaTa2O7 precursor prepared with nearly stoichiometric Rb (Rb/La = 1.2) resulted in the formation of impurities such as Ta3N5 and amorphous tantalum nitrides, the use of a Rb-rich precursor prepared with excess Rb (Rb/La = 2.4) effectively suppressed this impurity formation. The Rb+ cations in the prepared pure nitrogen-doped sample were exchanged with H+ to facilitate the intercalation of water, and a cationic Pt precursor was then selectively introduced into the interlayers and photocatalytically reduced to Pt metal particles. The internally platinized H+/RbLaTa2O7−xNy showed stable H2 evolution in the presence of I as an electron donor under visible light, accompanied by the generation of I3. Although the externally platinized H+/RbLaTa2O7−xNy sample and other bulk-type photocatalysts such as Ta3N5 generated H2 in the presence of a sacrificial electron donor, H2 evolution was negligible in the presence of I. The stable H2 evolution over the internally platinized H+/RbLaTa2O7−xNy sample is due to the suppressed backward reduction of I3 to I at selective reduction sites in the interlayer spaces, which are accessible only to cationic species and water.

Graphical abstract: Design of nitrogen-doped layered tantalates for non-sacrificial and selective hydrogen evolution from water under visible light

Supplementary files

Article information

Article type
Paper
Submitted
27 May 2016
Accepted
21 Aug 2016
First published
22 Aug 2016

J. Mater. Chem. A, 2016,4, 14444-14452

Design of nitrogen-doped layered tantalates for non-sacrificial and selective hydrogen evolution from water under visible light

H. Suzuki, O. Tomita, M. Higashi and R. Abe, J. Mater. Chem. A, 2016, 4, 14444 DOI: 10.1039/C6TA04416F

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